THE BENEFITS OF HYDRATED LIME - National Lime Association

The Benefits ofHYDRATED LIME INHOT MIX ASPHALTWritten By:Dallas N. LittleandJon A. Epps2001Hydrated lime in hot mix asphalt(HMA) creates multiple benefits.Updated By:Peter E. Sebaaly2006April 2006Prepared for the National Lime Association

TABLE OF CONTENTSPageSUMMARY.....................................................................................................................................8BACKGROUND .............................................................................................................................8Definitions and Mechanisms................................................................................................8History - Observed U.S. Pavement Problems......................................................................9Test Methods to Assess Stripping and Moisture Damage .................................................10LIME AS AN ANTI-STRIP AGENT............................................................................................12EXTENDED BENEFITS OF LIME IN HMA ..............................................................................15The Benefits of Hydrated Lime as a Mineral Filler and inMitigating the Effects of Oxidative Aging ............................................................15United States Research ..........................................................................................15European Research.................................................................................................18Plasticity of Fine Aggregate and Coatings.........................................................................20EFFECTIVENESS OF LIME IN COLD IN-PLACE RECYCLING............................................21IMPACT OF LIME ON THE MECAHNICAL PROPERTIESOF HMA MIXTURES...................................................................................................................23IMPACT OF LIME ON PAVEMENT LIFE AND LIFE CYCLE COSTS..................................26METHODS USED TO ADD LIME TO HMA .............................................................................25Laboratory and Field StudiesAssessing Methods of Lime Addition .............................................................................27Addition of Lime in the Hot Mix Plant..................................................................27Addition of Lime to Selected Fractions of Stockpiles...........................................29CONCLUSIONS............................................................................................................................30REFERENCES ..............................................................................................................................32

LIST OF TABLESTablePage1 Relative Behavior of Lime and Liquid Antistrip Additives in Georgia[Collins (1986)]..................................................................................................................362 Deformation (mm) After 20,000 Passes for Samples Treated with VariousAnti-Stripping Treatments in Colorado [Aschenbrener and Far (1994)]...........................363 Tabulations of Stripping Rate [Watson (1992)].................................................................374 Recommended Binder Contents for Optimum Durability of HMA Mixtures[Ishai and Craus (1996)] ...................................................................................................385 Impact of Lime Treatment on the Performance of Texas HMA Mixtures under theHamburg Wheel Tracking Device [Tahmoressi (2002)] ..................................................386 Tensile Strength Properties of Untreated and Lime Treated Mixture on the LoganInternational Airport [Mallick et al. (2005)] .....................................................................397 Impact of Multiple Freeze-thaw Cycling on the Rutting Potential of Liquid and LimeMixtures from the Idaho SH67 Project [Sebaaly et al. (2005)] ........................................398 Mechanical Properties of Lime and Liquid Mixtures from the Idaho SH67 Project[Sebaaly et al. (2005)] .......................................................................................................409 Plastic Shear Strains at 5,000 Cycles and Corresponding Rut Depth of North CarolineMixture, 50oC [Tayebali and Sidhore (2005)] .................................................................4010 Number of Cycles Corresponding to 7.5 mm and 5.0 mm Rutting in SpecimensTested by ASTEC Asphalt Pavement Tester [Collins et al. (1997)] .................................4111 Summary of Creep Test Data Evaluated According to theProcedure Developed by Little et al. [1994]......................................................................4112 Comparison of High Temperature Properties of the Un-aged and Aged Binders[Petersen et al. (1987)] ......................................................................................................4213 Comparison of Low Temperature Properties of the Un-aged and Aged Binders[Petersen et al. (1987)] ......................................................................................................4214 Impact of Hydrated Lime on the Properties of the Recovered Aged Binder from HMAMixtures in Spain [Rescasens et al. (2005)] .....................................................................4315 Mix Design Properties of the Nevada CIR Mixtures [Sebaaly et al. (2004)] ...................43ii

16 Impact of Hydrated Lime on the Torsional Fatigue Life of Sand Asphalt Mixtures[Little and Kim (2002)] .....................................................................................................4417 Impact of Lime Treatment and Lime Application Methods on the Mechanical Propertiesof Nevada’s HMA Mixtures [McCann and Sebaaly (2003)] ............................................4418 Ratio of E* with Lime to E* without Lime [Witczak and Bari (2004)] ...........................4419 Reasons for Using Lime in HMA Pavements [Hicks and Scholz (2003)] .......................4520 Typical Cost for Adding Lime into HMA Mixtures based on Contractors Surveys[Hicks and Scholz (2003)] ................................................................................................4521 Summary of the Life Cycle Cost Analysis of HMA Pavements with and without Limebased on the Deterministic Approach [Hicks and Scholz (2003)] ....................................4622 Summary of the Performance of Field Projects based on PMS Data[Sebaaly et al. (2003)] .......................................................................................................4723 Impact of Lime Treatment on Pavement Life in Nevada based on AASHTO DesignGuide [Sebaaly et al. (2003)] ............................................................................................4724 Performance of HMA Pavements in Northeast Texas based on Hamburg Rut Depth andVisual Performance Rating [Tahmoressi and Scullion (2002)]. .......................................4825 Nevada DOT Moisture Sensitivity Data of 97-99 HMA Mixtures[Epps Martin et al. (2003)] ................................................................................................4926 NDAOT Moisture Sensitivity Properties of HMA Mixtures at Various Marination Times[Epps Martin et al. (2003)] ................................................................................................49iii

LIST OF FIGURESFigurePage1 Extent of Moisture Damage in the United States [Hicks (1991)]...................................502 Percentage of Pavements Experiencing Moisture Related Distress by State[Hicks (1991)].................................................................................................................503 Distribution of Moisture Damage Treatments [Aschenbrener (2002)] ..........................514 Effect of Freeze-Thaw on Resilient Modulus [Epps et al. (1992)].................................515 Effect of the Number of Freeze-Thaw Cycles on Retained Tensile Strengthfor Various Additives [Epps et al. (1992)]......................................................................526 Effect of Degree of Saturation on the Tensile Strength Ratio[Kennedy and Ping (1991)].............................................................................................527 Relative Effectiveness of Mixture Tests Procedures to IdentifyMoisture-Related Problems [Hicks (1991)]....................................................................538 Type of Tests used to Assess Moisture Susceptibility of HMA Mixtures[Aschenbrener (2002)] ...................................................................................................539 Testing Stage for Moisture Susceptibility of HMA Mixtures[Aschenbrener (2002)] ...................................................................................................5410 Effect of Selected Modifiers on Moisture Damage as Measured bythe Freeze-Thaw Pedestal Tests [Kennedy and Ping (1991)].........................................5411 Effect of Various Additives on the Retained Strength (Following LottmanConditioning) of Asphalt Mixtures with 6.0% Asphalt Cement [Epps (1992)] .............5512 Multiple Freeze-Thaw Cyclic Tests Results for Laboratory Mixtures ComparingSeverity of Test Methods on the Ability to Differentiate BetweenLime and Other Anti-Strip Additives [Kennedy and Ping (1991)].................................5613 The Effect of Additives on Fatigue Life - Oregon Department of HighwaysField Study [Kim et al. (1995)].......................................................................................5814 Effect of Additives (Without Moisture) on Permanent Deformation -Oregon Department of Highways Field Study [Kim et al. (1995)] ................................5815 Effect of Additives (With Moisture) on Permanent Deformation -Oregon Department of Highways Field Study [Kim et al. (1995)] ................................59iv

FigurePage16 Effect of Hydrated Lime on the Resilient Moduli Before and Following LottmanConditioning for Truckee and Grass Valley, California Mixtures[Epps et al. (1992)] .........................................................................................................5917 Effect of Hydrated Lime on the Resilient Moduli Before and Following LottmanConditioning for Mammoth and Monroe, California Mixtures[Epps et al. (1992)] .........................................................................................................6018 Relative Effectiveness of Additives in Eliminating or ReducingMoisture Problems [Hicks (1991)] .................................................................................6019 Effect of Time on the Average Diamentral Tensile Strength Based onCores from Georgia Field Study [Watson (1992)] .........................................................6120 Severity of Stripping as Determined by Maupin for Virginia Pavements[Maupin (1995)]..............................................................................................................6221 Average Stripping in Fine Aggregate [Maupin (1997)] .................................................6222 Mr Property as a Function of Freeze-Thaw Cycles for the Mixtures on SD 314[Sebaaly et al. (2003)] ....................................................................................................6323 Mr Property as a Function of Freeze-Thaw Cycles for the Mixtures on US 14[Sebaaly et al. (2003)] ....................................................................................................6324 Relationship between Mr and F-T Cycles for Idaho SH67 Mixtures[Sebaaly et al. (2005)] ....................................................................................................6425 TSR Values of the North Carolina Mixtures with Baghouse Fines[Tayebali and Sidhore (2005)] .......................................................................................6426 Effect of the Addition of Hydrated Lime on Asphalt Binder Rheology, G*/sin δ[Little (1996)]..................................................................................................................6527 Creep Strains Measured After Lottman Conditioning on Natchez, Mississippi AsphaltMixture [Little (1994)]....................................................................................................6528 Lime Added to Hot Mix in Various Modes (to the Aggregate or to the Bitumen)Strongly Affects the Rut Resistance of the Mixture, Even Under High Temperature andMoisture [Lesueur et al. (1998)] .....................................................................................66v

FigurePage29 Hydrated Lime Improves Low Temperature Toughness of the Lime-Modified Bitumen[Lesueur et al. (1999)].....................................................................................................6630 Hydrated Lime Added to the Bitumen Improves the Toughness of the Bitumenand Improves Fatigue Life When Compared to the Identical Mixture Without Lime[Lesueur et al. (1998)].....................................................................................................6731 Effect of Hydrated Lime in Reducing the Aging Index of Asphalt Binders[Petersen et al. (1987)]....................................................................................................6732 Aging Index of Untreated and Lime-treated Asphalt Binders[Huang et al. (2002)] ......................................................................................................6833 Field Data Demonstrating the Effect of Hydrated Lime on the Hardening of AsphaltBinder Based on Utah Data [Jones (1997)] ....................................................................6934 Results of Rut Tracking Tests From Wuppertal-Dornap, Germany[Radenberg (1998)].........................................................................................................6935 Tensile Strength Ratio (TSR) and Resilient Modulus Ratio (MRR) of Kansas CIRMixtures [Cross (1999)] .................................................................................................7036 Percent Increase in Rut Depth in the APA Underwater after 8,00 Cycles ofKansas CIR Mixtures [Cross (1999)] ............................................................................7037 Average and Low Values of PSI for Untreated and Lime-Tretaed Mixtures on I-80 inNorthern Nevada [Sebaaly et al. (2003)] .......................................................................7138 Effect of the Method of Hydrated Lime Addition on the Retained ResilientModulus after Lottman Conditioning [Waite et al. (1986)]............................................7239 Effect of the Type of Additive and Method of Addition on the RetainedTensile Strength of Materials from SR-50, Millard County Lime to Salina, Utah[Betenson (1998)] ...........................................................................................................7240 Effect of Method of Lime Addition on Tensile Strength Ratio for Materials from I-70Wetwater to Colorado Line, Utah DOT [Betenson (1998)] ...........................................7341 Effect of Method of Lime Addition on the Retained Compressive and TensileStrengths for Main Street in Richfield, Utah [Betenson (1998)]....................................7342 Effect of Method of Lime Addition on the Retained Compressive and TensileStrengths for I-70 Spring Canyon to Wide Hollow, Utah [Betenson (1998)] ................74vi

FigurePage43 Effect of the Addition of Lime and Method of Addition on theRetained Stability for Georgia DOT Mixtures [Collins (1998)].....................................7444 Effect of Method of Application on Retained Tensile Strengths ofBatch Plant Operations in Texas [Button and Epps (1983)]...........................................7545 Effect of Addition of Lime to Drum Plant Operations[Button and Epps (1983)]................................................................................................7546 Impact of Lime Addition Method [Tahmoressi and Mikhail (1999)].............................7647 Effect of Method of Addition of Lime on Tensile Strength Ratio forBatch and Drum Plants [Button (1984)] .........................................................................7648 Effect of Amount of Lime Added to Field Sand [Kennedy et al. (1982)]......................7749 Effect of Time of Stockpile Marination on the Tensile Strength Ratio ofMississippi Siliceous River Gravel Aggregate [Little (1994)] .......................................7750 Effect of Method of Lime Addition and Percent of Lime Added toGranite Aggregate [Hanson et al. (1993)].......................................................................7851 Effect of Exposure Time and Stockpile Carbonation on theActive Ca(OH) 2 Remaining [Graves (1992)] .................................................................79vii

THE BENEFITS OFHYDRATED LIME INHOT MIX ASPHALTSUMMARYHydrated lime in hot mix asphalt (HMA)creates multiple benefits. A considerableamount of information exists in thecurrent literature on hydrated lime’sability to control water sensitivity and itswell-accepted ability as an antistrip toinhibit moisture damage. However, recentstudies demonstrate that lime alsogenerates other effects in HMA.Specifically, lime acts as an active filler,anti-oxidant, and as an additive thatreacts with clay fines in HMA. Thesemechanisms create multiple benefits forpavements:1. Hydrated lime reduces stripping.2. It acts as a mineral filler, stiffening theasphalt binder and HMA.3. It improves resistance to fracturegrowth (i.e., it improves fracturetoughness) at low temperatures.4. It favorably alters oxidation kineticsand interacts with products ofoxidation to reduce their deleteriouseffects.5. It alters the plastic properties of clayfines to improve moisture stability anddurability.The ability of lime to improve theresistance of HMA mixtures to moisturedamage, reduce oxidative aging, improvethe mechanical properties, and improveresistance to fatigue and rutting, has ledto observed improvements in the fieldperformance of lime-treated HMApavements. Life cycle cost analyses haveshown that using lime results inapproximate savings of $20/ton of HMAmix while field performance data showedan increase of 38% in the expectedpavement life.Several highway agencies have proven theeffectiveness of lime with cold-in-placerecycled mixtures. Lime treatment of theCIR mixtures increases their initialstability which allows the early opening ofthe facility to traffic and improves theirresistance to moisture damage whichsignificantly extends the useful life of thepavement.Various methods are used to add hydratedlime to HMA. They range from adding drylime to the drum mixer at the point ofasphalt binder entry, to adding lime toaggregate followed by “marination” forseveral days. This report summarizesstudies evaluating different modes ofapplication. Because different methodshave been used successfully, preferredmodes of application vary from state tostate. In 2003, the NLA produced anoverview of how to add lime to HMAmixtures based on site visits(http://www.lime.org/howtoadd.pdf).Hydrated lime is an additive that increasespavement life and performance throughmultiple mechanisms. This documentconsolidates recent studies and updatesprevious literature compilations onhydrated lime’s multiple benefits.BACKGROUNDDEFINITIONS ANDMECHANISMSStripping is commonly defined as "loss ofadhesion between the aggregate surfaceand asphalt cement binder in the presenceof moisture." HMA may experience loss ofstrength in the presence of moisturewithout visible evidence of debondingbecause water may affect the cohesivestrength of the asphalt binder. Thus, theterms "water susceptibility" and "watersensitivity" are often used to designatethe loss of strength or other properties ofHMA in the presence of moisture.8

The water susceptibility of HMA iscontrolled by:• Aggregate properties• Asphalt cement binder properties• Mixture characteristics• Climate• Traffic• Construction practices• Pavement design considerationsIt is usually the aggregate properties thatdominate the water susceptibilityproperties of an HMA. Although asphaltcement properties may also affect watersusceptibility, generally an aggregaterelatedwater susceptibility problemcannot be overcome by selecting anunmodified asphalt cement binder withsuperior antistripping properties.Problem pavements under high trafficlevels normally experience more rapidpremature distress than similarpavements under low traffic loading.Compacted mixtures with high air voidsare generally more likely to experiencestripping than pavements that arecompacted to low air void contents.The hot and wet climates of the southernUnited States and the cold and relativelydry climates of the western United Statesexperience the most dramatic strippingproblems. In the southeastern states, thecombination of high temperatures (lowasphalt viscosity) and wet weather (in thesummer months) cause stripping. Themountain and high desert areas of thewest experience severe stripping problemsdue to moisture, freeze-thaw cycles (up to230 air freeze-thaw cycles annually), andaggregates that have poor adhesion toasphalt in the presence of moisture. Mostother regions also experience moistureproblems that can manifest themselvesthrough incompatibility between bindersand aggregates and/or loss of cohesion inthe bitumen due to moisture penetration.Pavements with open-graded frictioncourses and interlayers (fabric, chip seals,etc.) have experienced premature distressdue to stripping. In fact, failures ofasphalt pavements within weeks of placingchip seals have occurred relativelyfrequently.The physical-chemical mechanismsresponsible for stripping in asphaltaggregatemixtures are complex and maynever be fully understood. Detachment,displacement, emulsification, pore waterpressure, hydraulic scouring, and asphaltaggregateinterfacial physical-chemistryhave been proposed to define the cause ofwater susceptibility problems. Additionalresearch will be needed for a fullunderstanding of the basic mechanisms.Nonetheless, the research presented inthis report demonstrates lime’s potentialfor creating multiple benefits in HMA andeffecting significant improvements inpavement performance.HISTORY – OBSERVED U.S.PAVEMENT PROBLEMSIn the late 1970s, a number of prematureasphalt pavement failures occurred in thesoutheastern and western United States.Stripping was identified as a majorproblem, but its rather suddenappearance has never been fullyexplained. Probable causes included:changes in properties of asphaltsassociated with the Arab oil embargo ofthe mid 1970s, increases in traffic, drummixing equipment, open graded frictioncourses, paving fabrics, and aggregatecharacteristics.A National Cooperative Highway ResearchProject (NCHRP), which was completed in1991, presented a more comprehensivereview of moisture damage problems[Hicks (1991)]. About 70 percent of theresponding state and provincedepartments of transportation in NorthAmerica experienced moisture damageproblems in their pavements. Figure 1shows that all regions reported moisture9

damage. Figure 2 shows the percentage ofpavements experiencing moisture-relateddistress by state.The major types of premature distressincluded: rutting or permanentdeformation in the wheel paths, bleedingin selected areas of the pavement, andalligator cracking. Millions of dollars ofrehabilitation were necessary andresearch efforts were initiated to solve thisproblem.Since the 1991 survey, many morestates have identified moisture as asignificant cause of pavement damage. In2002, the Colorado Department ofTransportation conducted a survey toidentify the actions that various agenciestake in combating moisture damage ofHMA mixtures [Aschenbrener (2002)].This survey included 50 state departmentsof transportation, 3 FHWA Federal Landoffices, the District of Columbia, and 1Canadian province. It was determinedthat 82% of the agencies require somesort of antistrip treatment. Figure 3shows the distribution of the varioustechniques used for moisture damagetreatment. Since the publication of the2002 survey, additional states have beguntreating asphalt mixes for stripping, suchas Kansas, and Vermont. After years ofalternate treatment methods to addresspavement damage, and after a thoroughstudy of alternate methods, the NebraskaDOT chose to specify hydrated limeexclusively as the preferred method oftreatment for their pavements.TEST METHODS TO ASSESSSTRIPPING AND MOISTUREDAMAGEThese moisture damage problemsstimulated considerable research in theUnited States in the late 1970s and duringthe 1980s. NCHRP projects were initiatedto develop improved water sensitivitytests for HMA [Lottman (1978), Lottman(1982), and Tunnicliff and Root (1982)].The present AASHTO and ASTM testmethods were developed based on thisresearch (AASHTO T 283 and ASTM D4867).Additional research was conductedin the 1990s and 2000s under theStrategic Highway Research Program(SHRP), NCHRP project 9-13;“Compatibility of a Test for Moisture-Induced Damage with SuperpaveVolumetric Mix Design,” and NCHRPproject 9-34; “Improved ConditioningProcedure for Predicting the MoistureSusceptibility of HMA Pavements.”Numerous test methods have beendeveloped to determine the watersusceptibility of HMA and other types ofasphalt aggregate combinations. Most ofthe tests are intended for use during themixture design process and are notsuitable for quality control and qualityassurance purposes. For the most part,extensive data are not available tocorrelate laboratory tests and fieldperformance.Laboratory tests for water susceptibilitycan be grouped into three mixturecategories: loose, representative, andcompacted.• Loose mixture tests includesoaking and boiling tests (e.g.,ASTM D 3625) performed on looseor uncompacted mixtures.• Representative mix tests areperformed on a selected portion ofthe aggregate fraction (forexample the fine aggregate). Oneexample is the “pedestal freezethawtest.”• Compacted mix tests comprisemost of the testing presentlyperformed in the United States.The immersion compression (ASTMD 1075), Root-Tunnicliff (ASTM D4867), and Lottman (AASHTO T283) tests are the most widely10

used. AASHTO T 283 with 6-inchdiameter samples is part of thevolumetric mixture design protocolfor Superpave.• Also under the compacted mixcategory, the environmentalconditioning system (ECS)developed in the SHRP researchand the Hamburg wheel trackingdevice are the latest group of teststo be introduced to assess themoisture susceptibility of HMAmixtures. A common featureamong these two tests is that theyattempt to simulate fieldconditions. The ECS simulates fieldconditions by simultaneouslyapplying repeated loads andmoisture flow while the Hamburgdevice applies repeated tire loadsover a submerged HMA sample.Important features of a water sensitivitytest include: compaction of the HMA to anair void content typical of that which isachieved at the time of construction (sixto eight percent), ensuring that thesample is exposed to water (using avacuum saturation procedure), andexposing the sample to a severe testenvironment (freeze-thaw cycle or cycles).Recent developments through the ECSand Hamburg tests attempted toincorporate simulations of field loadingconditions into the laboratory testingprocess.It is important that the air voids and thedegree of saturation be controlled inwhatever test method is used. Thevacuum saturation level and freeze-thawcycles to stress the bond at the interfaceof the asphalt binder and aggregate mustalso be controlled. Figure 4 indicates theimportance of the freeze-thaw cycle,Figure 5 the effect of multiple freeze-thawcycles, and Figure 6 the importance ofcontrolling the saturation level.North America, which indicate that theAASHTO T 283 test with modulus ortensile strength ratio is the most effectivemethod [Hicks (1991)]. The 2002Colorado DOT survey also collected dataon the type of test used to measuremoisture susceptibility and the stage atwhich the test is conducted [Aschenbrener(2002)]. It was found that 87% of theagencies test the HMA mix for moisturesensitivity. Figure 8 presents the varioustesting techniques that the agencies useto evaluate moisture susceptibility of HMAmixtures. Figure 9 shows the stage atwhich the agencies test for moisturesusceptibility: 62% test at the mix designstage only and 38% test at both the mixdesign and construction stages. Thesurvey also concluded that 20% of theagencies continue to fund research onmoisture damage of HMA mixtures.Based on the 1991 and 2002surveys, the AASHTO T 283 and othertensile strength ratio (TSR) tests areperceived to be the most effective. TheAASHTO T 283 with a single freeze-thawcycle is the best standardized testpresently used in the United States. Theuse of multiple freeze-thaw cycles haveshown to increase precision and toimprove correlations with actual fieldperformance. The percentages ofagencies using the various tests, based onthe 2002 survey, are summarized below:• 82 % use tensile test (AASHTO T283, ASTM D 4867, or similar),• 10% use a compression test(AASHTO T 115 or similar),• 4% use a retained stability test(typically the Marshall stability),and• 4% use wheel-track tests (eitherthe Hamburg or the APA) andtensile tests.Figure 7 summarizes the findings of the1991 survey of states and provinces in11

LIME AS AN ANTISTRIP AGENTA number of additives to reduce moisturesensitivity and stripping are used in theUnited States. Hydrated lime is widelyused as an antistrip additive. Othersinclude liquid additives (e.g. amines,diamines, and polymers), portlandcement, fly ash, and flue dust. Pavementcontractors usually prefer liquid antistripadditives as they are relatively easy touse. Figure 10 shows results from thefreeze-thaw pedestal test indicating therelative antistripping properties of varioustypes of additives. These data show thatsome liquid antistrip additives reduce theresistance of HMA mixtures to moisturedamage. Figure 11 shows the results ofLottman tests on Nevada HMAs, whichcontain different types of antistripadditives [Epps (1992)]. The higherretained strength after Lottmanconditioning when hydrated lime is addedillustrates its value in reducing moisturedamage.Figure 12 illustrates that the relativeeffectiveness of liquid antistrip agents andlime depends on the aggregate type andthe test method used to evaluate the HMA[Kennedy and Ping (1991)]. In general,the more severe the laboratory testmethod, the more demonstrable thedifferences between lime and liquidantistrip agents.The relative effect of lime versus variousliquid antistrip agents in Georgia HMAmixtures is shown in Table 1 [Collins(1988)]. The conditioned samplesreported in this table were subjected tovacuum saturation without freeze-thawcycles. Values reported are state-wideaverage values. In all but one case, limeoutperformed the other antistrippingagents.Colorado used the Hamburg wheeltracking device to evaluate the relativeeffectiveness of different types ofantistripping agents (Table 2). Theaddition of hydrated lime producedmixtures that passed the test acceptancecriteria for all four HMAs. Some of theliquid antistrip agents did not producesatisfactory results [Aschenbrener and Far(1994)].A study conducted by Oregon StateUniversity for the Oregon DOTdemonstrated that both fatigue andrutting resistance can be improved withlime [Kim et. al., (1995)]. Figure 13indicates that the addition of hydratedlime will increase the fatigue life of apavement as determined by a laboratoryfatigue test. Figures 14 and 15 show thatlime reduces permanent deformation orrutting of pavements. These data alsoindicate that lime performs better thanliquid antistrip materials.Results of laboratory studies on Californiaaggregates are shown in Figures 16 and17 [Epps (1992)]. The antistrip benefits ofadding lime to these aggregates and thisasphalt binder are evident. The modifiedLottman test (AASHTO T 283) was used inthis study.Results of a survey of perceptions of theeffectiveness of various antistrippingagents are shown on Figure 18 [Hicks(1991)]. Lime has a higher effectivenessrating than liquid antistrip agents(amines), polymers, and portland cement.Georgia DOT conducted a field evaluationprogram involving more than 125 pavingprojects [Watson (1992)]. Core samples(of lime-treated HMA) were obtained fromthese projects and a visual evaluation ofstripping was made--see Table 3. Some ofthese cores were from pavements morethan 10 years old. Average tensilestrengths of these core samples areshown on Figure 19. The effectiveness oflime as an antistripping agent isdemonstrated by the constant level of thetensile strength of the field cores as afunction of pavement age.12

Virginia conducted field evaluations ofpavements that were three to four yearsold—see Figure 20 [Maupin (1995)]. Ofthe 12 pavements included in the study,the pavements in which lime was used asan antistrip agent had only “very slight” to“slight” stripping as determined from coresamples obtained from the pavements andfrom visual evaluations of the pavementsurface. The lime-treated HMA sectionsdisplayed lower water sensitivity than thesections that were treated with chemicalliquid additive. Two years later, adifferent set of pavements were sampledand evaluated after five to six years ofservice [Maupin (1997)]. Results fromthis study indicate little differencebetween the lime-treated and liquid-antistrip-treatedHMA sections as shown inFigure 21. However, this study wasconducted on non-experimental testsections – in contrast to the earlier, morescientifically-structured and well-designedstudy.Tarrer (1996) investigated the bitumenaggregatebond and concluded that, in thefield, the water at the surface of theaggregate has a high pH and thereforemost liquid antistrip agents remain at thesurface because they are water soluble athigh pH levels. To overcome being washedaway, the liquid antistripping agents mustbe given time to cure (in excess of threehours). In contrast, hydrated lime curesrapidly (within 15 to 30 minutes) andforms water insoluble compounds.Hydrated lime creates a very strong bondbetween the bitumen and the aggregate,preventing stripping at all pH levels.Tarrer also found that hydrated limereacted with silica and alumina aggregatesin a pozzolanic manner that addedconsiderable strength to the mixture.In 1996 Ishai and Craus compared theimpact of six different fillers on thedurability of HMA mixtures under moistureconditioning [Ishai and Craus (1996)].The durability index was defined as theaverage strength loss area enclosedbetween the durability curve and initialstrength line. The researchers found thatmixtures with non-active fillers are muchmore sensitive to binder contents thanmixtures with active filers. Using therelationships between durability index andbinder contents for the various fillers, theresearchers recommended the optimumbinder contents for the various fillers toachieve the optimum durability of themixture. The data in Table 4 indicate thatby using hydrated lime as a filler in HMAmixtures, the optimum binder content formaximum durability is a minimum of0.5% lower than any other filler. Thisreduction in the optimum binder contenttranslates into direct construction costsavings.Tahmoressi reported on a Texas DOTstudy to evaluate the impact of limetreatment on the performance oflimestone mixtures in Texas under theHamburg wheel tracking device[Tahmoressi (2002)]. The study evaluatedthe performance of Texas mixtures usingsoft, moderate, and hard limestoneaggregates with PG64-22, PG70-20, andPG76-22 binders. The research concludedthat the addition of 1% hydrated limereduces the Hamburg rut depth by 50percent for all binder grades and it isequivalent to raising the PG binder gradeby one grade. The report also presentedextensive data on the resistance of HMAmixtures to rutting under the Hamburgwheel tracking device conducted by theTexas DOT. TxDOT uses a Hamburgfailure criterion of a 12.5 mm rut depthunder 20,000 load cycles. Table 5summarizes the TxDOT data whichindicate that limestone, gravel, andigneous aggregates all show significantincrease in the number of mixes passingthe TxDOT Hamburg criterion by theaddition of lime regardless of the bindergrade.The South Dakota DOT compared theperformance of various antistrip additiveson two field projects [Sebaaly et al.(2003)]. Each project included a controlsection and five sections treated with13

lime, liquid, and ultrapave (UP) additives.Figures 22 and 23 show the performanceof the field mixtures under multiplefreeze-thaw cycling in the laboratory.The resilient modulus (Mr) is anengineering property that describes thestress-strain relationship of the HMA mix.A reduction in the Mr property undermultiple freeze-thaw cycling leads to anincrease in the strains experienced by theHMA mixture due to traffic inducedstresses. As the HMA pavement issubjected to higher strains, its tendencyto experience rutting and fatigue crackingwould increase. The data show thatmixtures treated with hydrated limeperformed significantly better than thecontrol, UP5000, and the liquid antistripmixtures at both locations.Moisture damage was identified as thecause of failure of HMA mixtures with twodifferent aggregates at the LoganInternational Airport in Boston. Theimpacts of lime treatment of the twomixtures and an additional mixture with athird aggregate were evaluated usingmultiple freeze-thaw cycling and loadingunder the Model Mobile Load Simulator 3(MMLS3) [Mallick et al. (2005)]. TheMMLS3 subjects the six-inch diametersamples to repeated tire loads of 607 lbsand 100 psi while submerged under 140oFwater. The tensile strength (TS) propertywas used to measure the impact of bothmultiple freeze-thaw cycling and theMMLS3 trafficking. Table 6 shows that theaddition of hydrated lime significantlyimproved the unconditioned andconditioned TS and TSR of mixtures. Itwas concluded that lime treatment waseffective in improving the resistance ofthe mixtures to moisture damage inducedby hot-wet trafficking (MMLS3) and undermultiple freeze-thaw cycling.In 2005 the Idaho DOT constructed a fieldproject on SH67 to evaluate the impact oflime and liquid antistrip on the mechanicalproperties of an Idaho HMA mix [Sebaalyet al. (2005)]. Both the lime and liquidmixtures were evaluated under multiplefreeze-thaw cycling in the laboratory asshown in Figure 24. The lime mix startedat a higher dry Mr property andmaintained good modulus properties overthe entire 21 freeze-thaw cycles. Theliquid mix fully disintegrated after 22freeze-thaw cycles. The results of amechanistic analysis summarized in Table7 show that, as a result of multiple freezethawcycling, the liquid mix will have 220percent increase in potential rutting ascompared to the lime mix having only 65percent potential increase in rutting.Table 8 summarizes the followingmechanical properties of the lime andliquid mixtures:• Dynamic modulus in compressionas an indicator of rutting resistance• Dynamic modulus in tension as anindicator of moisture damage• Rate of dynamic creep as anindicator of fatigue resistanceBased on the mechanical properties of thelime and liquid mixtures at the moistureconditioned and unconditioned stages, theresearchers concluded that the lime mix isstiffer, less susceptible to rutting, and lesssusceptible to moisture damage whilehaving similar fatigue cracking comparedto the liquid mix.A recent study by the North Carolina DOTevaluated the use of lime as an anti-stripadditive for mitigating moisture sensitivityof asphalt mixes containing baghousefines (BHF) [Tayebali and Shidhore(2005)]. The NCDOT uses a tensilestrength ratio of 85% as a failure criterionfollowing the AASHTO T-283 methodwithout the freeze-thaw cycle. Figure 25shows that the use of 1.0 percenthydrated lime improved the TSR ratios ofmixtures from the high 60s to the 85-95percent range which comply with theNCDOT TSR criterion. The researchersused the simple shear tester to measurethe permanent shear strains under 5,000cycles of shear stresses and used themeasured shear strains to estimate rutdepth. The data in Table 9 show that the14

lime treatment of the mixtures reducedthe estimated rut depth at the dry andwet stages.EXTENDED BENEFITS OF LIMEIN HMANot only does the addition of lime provideantistripping benefits, but it also:1. Acts as a mineral filler to stiffenthe asphalt binder and HMA;2. Improves resistance to fracturegrowth (i.e., improves fracturetoughness) at low temperatures;3. Favorably alters oxidation kineticsand interacts with products ofoxidation to reduce theirdeleterious effects; and4. Alters the plastic properties of clayfines to improve moisturesensitivity and durability.The filler effect of the lime in the asphaltreduces the potential of the asphalt todeform at high temperatures, especiallyduring its early life when it is mostsusceptible to rutting. The hydrated limefiller actually stiffens the asphalt film andreinforces it. Furthermore, the lime makesthe HMA less sensitive to moisture effectsby improving the aggregate-asphalt bond.This synergistically improves rutresistance. As the HMA ages due tooxidation, hydrated lime reduces not onlythe rate of oxidation but also the harmcreated by the products of oxidation. Thiseffect keeps the asphalt from hardeningexcessively and from becoming highlysusceptible to cracking (through fatigueand low temperature (thermal) cracking).Synergistically, the filler effect of thehydrated lime dispersed in the asphaltimproves fracture resistance and furtherimproves cracking resistance.In addition to these benefits, addinghydrated lime to marginal aggregates thathave plastic fines can improve theaggregate through the mechanisms ofcation exchange,flocculation/agglomeration, and pozzolanicreactions. These reactions result in achange in the characteristics of the finesso that they are no longer plastic but actas agglomerates held together by a“pozzolanic cement” [Little (1987)]. Thisprocess makes the aggregate fines muchless susceptible to moisture by reducingtheir ability to attract and hold water.THE BENEFITS OF HYDRATEDLIME AS A MINERAL FILLERAND IN MITIGATING THEEFFECTS OF OXIDATIVE AGINGThis section presents research on themultifunctional benefits of hydrated limein more detail. Research has beenconducted throughout the world--in theUnited States, Europe, Australia, andSouth Africa.UNITED STATES RESEARCHFigures 16 and 17 indicate that theaddition of hydrated lime to HMAincreases stiffness [Epps (1992)]. Thishelps to distribute and reduce the stressesand strains in the pavement structurecreated by traffic loads and generallyreduces rutting (permanent deformation)potential. The results of laboratory wheeltracking tests conducted in Colorado(Table 2) and Georgia (Table 10) indicatethat hydrated lime increases resistance torutting and permanent deformation[Aschenbrener and Far, (1994) and Collinset al., (1997)]. Creep tests in Texas(Table 11) also clearly show that hydratedlime promotes high temperature stability,thereby increasing resistance to rutting[Little (1994)].The mineral filler effect on asphalt isshown in Figure 26 and indicates that limesubstantially increases the stiffness ofasphalt cement binders. The propertyrepresented in Figure 26 is the parameter15

G*/sin δ, which has been adopted by theSuperpave performance grade (PG)system for asphalt binders as an indicatorof rut resistance. An increase in thisparameter increases the stiffness of theHMA and reduces the rutting potential.The increase in stiffness of the asphaltbinder also increases resistance to watersusceptibility. The synergistic effects ofmoisture resistance and improvedstiffness are demonstrated by the creeptest results in Figure 27. The experimentused a siliceous aggregate from Natchez,Mississippi treated with a lime slurry inthe stockpile - a marination process. Thestockpile was about 90 days old when itwas used to produce the HMA. The creeptests were conducted after the mix wassubjected to vacuum saturation. Theuntreated mix is extremely moisturesusceptible and creeps at an acceleratedrate (tertiary creep) after about 2,500seconds of loading. The lime-treated mixmaintains excellent creep properties(maintaining steady state behavior) andnever enters tertiary creep.Research studies conducted in the 1990sevaluated the impact of lime on theimprovements in high temperatureperformance (rutting resistance), fatiguecracking resistance, and low temperaturefracture [Little (1996), Lesueur et al.(1998), and Lesueur and Little (1999)].These studies concluded that:1. Hydrated lime is not simply aninert filler but reacts with thebitumen. The lime particles actuallyadsorb polar components of thebitumen. This adsorbed inter-layermakes hydrated lime a veryeffective additive. The level of thebitumen-lime reaction was found tobe bitumen dependent.2. The “active” filler effect has agraduated temperature sensitivity.At high temperatures the fillereffect is most pronounced; it isconsiderably less at temperaturesnear the glass transition of thebitumen. This very positivecharacteristic allows the bitumen toresist flow-damage at hightemperatures and yet to relax atlow temperatures, dissipatingenergy by flow in lieu of fracturing.3. A physico-chemical interactionbetween the hydrated lime and thebitumen can be verified by (a)rheological models, (b) nuclearmagnetic resonance, and (c)scanning electron microscopy.4. The physico-chemical interaction isa fundamental mechanism thatprovides a basis to explain themultifunctional effects of lime inbitumen. These effects include: (a)improved rut resistance (Figure28), (b) improved low-temperaturefracture toughness (Figure 29),and (c) improved fracture fatigueresistance (Figure 30).Extensive research at the WesternResearch Institute (WRI) shows that agehardening of asphalt binders can bereduced by the addition of hydrated lime[WRI (1997)]. In 1987, Petersen et al.evaluated two asphalt binders modifiedwith limestone and hydrated lime at 20percent by weight of binder. Theuntreated and treated binders were agedat 113 o C in the thin film accelerated agingtest. Table 12 summarizes the hightemperature properties of the untreatedand treated binders. For both binders,the addition of hydrated lime increasesthe un-aged complex modulus, reducesthe aged complex modulus, andsignificantly reduces the aging index(Figure 31). Table 13 summarizes themeasured low temperature properties ofthe untreated and treated aged bindersfrom the same experiment. In bothcases, the lime treatment of the bindersalmost doubled the percent elongation ofthe aged binders while it maintainedsimilar modulus to the untreated binder.This translates in significantimprovements in the resistance of theaged binders to thermal cracking. Theresults of this research indicate that lime16

treatment would improve the resistance offresh pavements to permanentdeformation through an increase in theun-aged high temperature complexmodulus and improves the resistance ofthe aged pavement to thermal crackingthrough the reduced aging index. Sincethe behavior of HMA mixtures at lowtemperatures is mainly controlled by theproperties of the aged binder, limetreatment would produce HMA pavementsthat are highly resistant to thermalcracking.In other research efforts, the WRIresearchers attempted to resolve some ofissues surrounding the laboratory testingof recovered asphalt binders from fieldagedmixtures [Huang et al. (2002) andHuang and Robertson (2004)]. Extractingand recovering an asphalt binder from alime-treated HMA mixture using powerfulsolvents would destroy any lime-inducedmolecular structuring that may be presentin the mix. Another question would bewhere does the lime go after the binder isrecovered. Furthermore, there is noassurance that the rheological propertiesmeasured in the recovered asphalt binderare representative of the actual in-placeproperties of the lime-treated asphalt inthe pavement. In light of these issues,the WRI researchers aged the untreatedand lime-treated binders in the pressureaging vessel (PAV) at 60 o C to simulatethe temperature ranges encountered inthe field. The PAV aging intervals werefor 100, 400, 800, and 2000 hours. Therheological properties of the un-aged andaged binders were measured at 25 o C and60 o C and 10 rad/s. Two asphalt bindersand two grades of hydrated lime wereused in the study. Both binders weretreated with 20 percent by weight ofbinder with the two grades of lime. Figure32 presents the relationship betweenaging time and aging index which isdefined as the ratio of the viscosity afterPAV aging over the viscosity before aging.The data in Figure 32 indicate that thelime was highly effective in reducing theaging index of the AAD-1 binder. Limetreatment was not as effective with theABD binder which is not a typical binder.It is well recognized that lime treatmentwould improve the aging characteristics ofmost asphalt binders.The WRI research adds further credibilityto the bitumen-hydrated-lime interaction.WRI’s research demonstrates thatcarboxylic acids in bitumens hydrogenbond very strongly with hydroxyl groupson siliceous aggregates. However, thehydrogen bonds are very sensitive todisruption by water. Conversion ofcarboxylic acids within the bitumen toinsoluble salts prior to mixing withaggregate should prevent adsorption ofthe water-sensitive free acids on theaggregate. WRI further notes that theconversion of all acidic materials in thebitumen to water-insensitive calcium saltsat the time of bitumen production wouldbe preferred.Furthermore, this reduction in hardeninghas been confirmed in a field studyconducted by the Utah DOT (Figure 33)[Jones (1997)].Buttlar et al., (1999) usedmicromechanics to assess the mechanicalproperties of mineral fillers combined withbitumen to form mastics. They concludedthat a rigid layer adsorbed to the fillerexplains the ability of the filler to result instiffening ratios that are greater thanwould be predicted based on volumetricconcentrations alone. Based on theequivalent rigid layer analysis, physicochemicalreinforcement effects play adominant role throughout the range offiller-to-bitumen ratios encountered inpractice. Hydrated lime shows a muchhigher level of physico-chemicalreinforcement than baghouse fillers. Theyfurther conclude that the surface activityof hydrated lime--and hence physicochemicalstiffening potential--is quite highand that the flaky shape and roughsurface texture of hydrated lime alsocontribute to stiffening effects whichexceed those predicted by volume-based17

models. The work of Buttlar et al., (1999),Lesueur, Little and Epps (1998), Lesueurand Little (1999), Hoppman (1998), andVanelstraete and Verhasselt (1998) areconsistent and in agreement on this topic.Johannson (1998) performed an extensivereview of the literature of lime in bitumenand conducted additional research on thereaction of hydrated lime with bitumen.Some of Johannson’s most significantfindings are:1. Adding 20 percent hydrated limeby mass of binder produces asignificant increase in creepstiffness but does not increasephysical hardening. Furthermore,the lime-modified bitumendemonstrates a greater potentialfor dissipating energy throughdeformation (at low temperature)than the unmodified bitumen. Thisis a positive effect at lowtemperatures because it reducesfracture potential.2. Although the filler effect increaseslow temperature stiffness, fracturetoughness is substantiallyincreased. Fracture toughness isthe energy expended in fracturinga material. Lesueur and Little(1999) also demonstrated that atlow temperatures lime does notnegatively impact relaxation butsubstantially increases fracturetoughness.3. Hydrated lime reduces the effectsof age-hardening more so at hightemperatures than at lowtemperatures.Little and Petersen (2005)synthesized several decades of researchconsidering the rheological andmechanical contributions imparted toasphalt mixtures by the addition ofhydrated lime. They concluded that dueto its chemical activity, hydrated limeadded as part of the mineral filler,improves stiffness at high temperatureswhile toughening mixes at lowtemperatures. Mixtures containinghydrated lime can accommodate morefatigue than either unfilled systems orthose containing equivalently sizedlimestone. They observed that “theimpact of hydrated lime as a filler and itsproven ability to resist damage is probablydue to a complex interaction of effectsrelated to a physical filler and the way inwhich hydrated lime affects the microstructuralnature of the bitumen.”EUROPEAN RESEARCHFrench ResearchFrench researchers recognize the effectsof hydrated lime in HMA in improvingstiffening as well as the aggregate-asphaltbond. The Jean Lefevre-Metz Companyand the Laboratoire Central des Ponts etChaussées (LCPC) in Saint Quentin,verified that hydrated lime makes asphaltroad courses more stable and reducesrutting [Mauget (1998)].German ResearchThe practical effectiveness of hydratedlime in HMA to improve moisturesensitivity and stiffening is accepted inGermany. Field research on two roadsections (L 280 near Grevenbroich and B7N near Wuppertal-Dornap) confirms thatthe addition of 1.0 to 1.5 percenthydrated lime by weight of the mixturecan substantially improve rut resistance[Radenberg (1998)]. Figure 34 illustratesthe results of wheel tracking tests fromthe Wuppertal-Dornap pavements.Belgian ResearchThe Centre de Recherches Routiéres(CRR) in Belgium has verified that limecreates a significant improvement inadhesion between binders and aggregates[Verhasselt (1996)]. CRR also identifies animprovement in resistance to the effectsof oxidative hardening [Verhasselt &Choquet (1993)].18

Some of the most powerful research inrecent years to demonstrate a limebitumeninteraction was performed byHopman et al., (1998). Results are similarto those reported by Lesueur, Little, andEpps (1998). Hopman et al., used lightabsorption measurements and gelpermeationchromatography (GPC). Bothmethods show a significant change ingeneric composition of the bitumen afterthe addition of lime--indicating that lime isan “active” filler.Spanish ResearchResearchers in Spain and Argentinarecently compared the impact of hydratedlime on the aging characteristics ofasphalt binders and mixtures [Recasens etal. (2005)]. The aging process consistedof placing the compacted HMA sample inthe oven at 80 o C for 0, 2, 4, and 7 days.The asphalt binder was extracted from theHMA mix after 2 and 7 days of oven agingand tested for penetration, absolute andkinematic viscosities, and softening point.Table 14 summarizes the properties of therecovered aged binder which show thatthe hydrated lime significantly reduces theaging rate of the asphalt binder. Thestudy also evaluated the impact ofhydrated lime and calcium carbonate onthe aging rate of HMA mixtures. Theimpact of aging on the brittleness of theHMA mix was evaluated through a directtension test on a notched Marshall sampleat 20 o C. The specific energy of fracturewas obtained as the area under the loaddisplacement curve divided by the area ofthe fracture of the sample. A higherspecific energy of fracture indicates amore brittle HMA mix with a lowerresistance to cracking. The data showedthat after 7-days of oven aging, the HMAmix with hydrated lime had a specificenergy of fracture that is 10 and 30percent lower than the un-filled mix andthe mix with calcium carbonate,respectively. The combination of lowerbinder properties and lower specificenergy of fracture with time indicates theprotective characteristics of hydrated limeagainst aging which ensures a better longterm durability of the HMA mix.PLASTICITY OF FINEAGGREGATE AND COATINGSAggregates that are used for HMA cancontain plastic clays and clay coatings.While generally not desirable, economicconsiderations sometimes dictate their usein HMA. Lime is an effective chemicaladditive for reducing the plasticcharacteristics of clay soils and iscommonly used for treating soils withplasticity index above about 10 [NLA(1999)]. Ion exchange on the clay surface(involving calcium ions), flocculation andagglomeration of the clay minerals, andpozzolanic reactions are responsible forthe effectiveness of lime [Little (1995)].EFFECTIVENESS OF LIME INCOLD IN-PLACE RECYCLINGRecycling of the existing pavement offersan attractive approach for effectivelydealing with the distressed pavementsurface. A severely cracked pavementpresents a challenge for the designengineer due to its potential of reflectingthe cracks through the new overlay.Recycling of the existing surface woulddelay the problem of reflective crackingand a strong base would result in therequirement of a thinner overlay.Cold in-place recycling (CIR) is defined asthe pulverization of the top 2” – 3” of theexisting HMA layer, mixing it withemulsion and repaving the mix on thesite. The objectives of the CIR processcan be summarized as follows:• Reduce the brittleness of the agedexisting mixture,• Provide a mixture with enoughstability for early traffic, and• Improve the moisture sensitivity ofthe mixture.20

Achieving the above objectives is criticalsince any HMA mixture selected for CIR isexpected to have experienced moisturedamage and/or aging. The combination ofthese two conditions results in a CIRmixture that is highly susceptible tomoisture damage. Several laboratory andfield studies have shown that the additionof hydrated lime to CIR mixturessignificantly improves their early stabilityand moisture sensitivity.Cross evaluated the impact of hydratedlime slurry on the moisture sensitivity ofCIR mixtures in Kansas [Cross (1999)].The AASHTO T-283 with one freeze-thawcycle was used to moisture condition thetensile strength and resilient modulussamples. Figure 35 shows the retainedtensile strength and resilient modulusratios (i.e. ratio of conditioned overunconditioned property) of the variousCIR mixtures. The data show that thehydrated lime slurry has a significantimpact on the retained tensile strengthratio while not as significant on theretained resilient modulus ratio except forthe high float emulsion where thehydrated lime slurry showed a significantimpact on both ratios. The research alsoevaluated the impact of hydrated limeslurry on the rut resistance of CIR mixtureas measured in the asphalt pavementanalyzer (APA) at the dry and underwaterconditions. Figure 36 presents theincrease in rut depth from the dry to theunderwater conditions which shows thesignificant impact of the hydrated limeslurry in reducing the percent change inthe rut depth of the CIR mixtures.As a follow-up to this study, the KansasDOT constructed field test sections in1997 to evaluate the long-termperformance of CIR mixtures treated withlime slurry and fly ash [Fager (2004)].The Kansas researchers concluded thefollowing: “The fly ash section crackedsoon after construction and had morecracking than the lime slurry section.Cracking in the lime slurry sectionoccurred much later….the lime slurrysection outperformed the fly ash testsection.”In the late 1990s, the Nevada DOT startedlooking into recycling most of the lowmediumvolume roads. A mix designprocedure for CIR mixtures was developedto provide early stability and resistant tomoisture damage [Sebaaly et al. (2004)].Table 15 summarizes the mix design datafrom three different CIR projects. A goodlevel of early stability was defined as anMr value above 150 ksi, and a goodresistance to moisture damage wasdefined as a retained-strength ratio above70%. Based on the mix designs data inTable 15, the Nevada researchersconcluded that in order to achieve earlystability and to improve resistance of themixtures to moisture damage, limetreatment of the CIR mixtures wasneeded. Currently, Nevada DOTmandates the use of lime in all CIRmixtures which has led to excellent fieldperformance [Sebaaly et al. (2004)].IMPACT OF LIME ON THEMECHANICAL PROPERTIES OFHMA MIXTURESMechanical properties of HMAmixtures play a major role in pavementdesign, analysis, and performance. Theygovern the relationships between trafficloads and pavement responses and thelong term performance of pavementstructures under the combined action oftraffic and environment. Typicalmechanical properties of HMA mixturesinclude the modulus as a function oftemperature and loading rate, and fatigueand rutting performance relationships. Asthe pavement engineering communitymoves closer to the implementation of theAASHTO Mechanistic-Empirical PavementDesign Guide (MEPDG), the knowledge ofthe mechanical properties of HMAmixtures becomes a high priority.21

An ideal HMA mix can becharacterized as having good modulusproperties under the anticipated fieldconditions and excellent fatigue andrutting resistance. When such an idealmix is incorporated into a mechanisticbasedpavement design, excellent longterm performance can be realized alongwith significant cost savings. Severalmaterials and mix design factors influencethe magnitude of the mechanicalproperties of HMA mixtures, such as:binder grade, aggregate gradation andquality, volumetric properties of the mix,and any modifications to the binder or theaggregate. Lime treatment of HMAmixtures has been shown to positivelyinfluence the mechanical properties ofHMA mixtures.Researchers at Texas A&M Universityevaluated the impact of rest periods onthe healing of HMA mixtures [Si et al.(2002)]. Different rest periods wereintroduced into the uniaxial fatigue testingof untreated and lime treated mixtureswith river gravel and crushed limestonemixtures from Texas. It is believed thatrest periods during fatigue testing bettersimulate field conditions since repeatedtraffic loading in the field always occursafter the pavement has time to recover.The healing index was defined as thepercent increase in the stiffness of theHMA mix after the introduction of the restperiod. The researchers concluded thatthe degree of healing is mixturedependent and the ability of a mixture toheal is largely related to binder properties.The addition of hydrated lime to themixtures tested generally improved thehealing potential of the mixtures.Little and his colleagues used the torsionalfatigue test to evaluate the impact of limetreatment on the fatigue life of sandasphalt mixtures [Little and Kim (2002)and Kim et al. (2003)]. The data in Table16 show that the effect of hydrated limeas a filler increased the high strain fatiguelife of the sand asphalt mix with binderAAD-1 by approximately 240 percent andthe fatigue life of the sand mix with binderAAM-1 by approximately 100 percent.Researchers also used the cumulativedissipated energy as an indication offatigue resistance which showed that theaddition of lime increased the fatigueresistance by 588 and 442 percent for theAAD-1 and AAM-1 binders, respectively.Researchers at the University of Nevadaevaluated the impact of hydrated lime onthe mechanical properties of HMAmixtures and assessed the differencesamong the various lime applicationtechniques [McCann and Sebaaly (2003)].Three different mixtures were evaluatedwith four lime application methods alongwith a control mix (i.e. no-lime). The fourmethods of lime applications were: drylime on moist aggregates with and without48 hours marination and lime slurry withand without 48 hours marination. Table 17summarizes the data based on theresilient modulus, tensile strength, andresistance to permanent shear strains. Itshould be noted that the label “NOTDIFFERENT” means that the no-lime mixhas similar property to the lime- treatedmix and the label “DIFFERENT” meansthat the no-lime mix has a property that issignificantly lower than the lime-treatedmix. The data in Table 17 indicate thatprior to moisture conditioning, the twomixtures had similar mechanicalproperties in the majority of the cases.However, when the mixtures weremoisture conditioned with one or 18freeze-thaw cycles, the mechanicalproperties of the no-lime mixtures weresignificantly lower than those of the limetreatedmixtures. In addition, the studyconcluded that the four methods of limeapplications did not have any significantimpact on the mechanical properties ofthe HMA mixtures.In an effort to incorporate lime-treatedHMA mixtures into the AASHTO MEPDG,Bari and Witczak measured the effect oflime on the dynamic modulus (E*) of HMAmixtures [Bari and Witczak (2005)]. TheAASHTO MEPDG uses E* as the primary22

material property for HMA mixtures.Therefore, any impact of lime-treatmenton the E* property of HMA mixtures willintroduce changes in the design of thepavement structure. The researchmeasured the E* properties of seventeendifferent mixtures sampled from sixdifferent project sites across the UnitedStates: six mixtures contain no lime andeleven mixtures had hydrated lime up to3% by dry weight of aggregate. The datain Table 18 show that the addition ofhydrated lime increases the dynamicmodulus of the HMA mix between 17 and50 percent. The researchers concludedthat the E* of a lime treated HMA mixture(1-2% lime) will be approximately 1.25times the E* of untreated mixturesindependent of temperature and/or timerate of load.Significant increases in the modulus,fatigue and rut resistance of the HMA mixleads to reduced layer thickness andbetter long term performance. In themechanistic pavement design process, theeffects of an increased modulus andimproved resistance to fatigue and ruttingare accumulated exponentially. In otherwords, the higher modulus would result inlower strains in the HMA layer. When thelower strains are introduced into theimproved fatigue and rutting relationships,a significant improvement in theperformance of the pavement is realized.IMPACT OF LIME ON PAVEMENTLIFE AND LIFE CYCLE COSTSThe impact on pavement life andits life cycle costs is the ultimate measureby which the effectiveness of an additivecan be assessed. Regardless of howeffective the additive is in improving theproperties of the various components orthe entire HMA mix, the ultimatechallenge is to construct a less expensivepavement that will last longer. Therefore,the final link in assessing the effectivenessof lime on HMA pavements is to take theimprovements that lime introduces on thevarious components and translate theminto extension in pavement life and lowerlife cycle costs. This task is huge andrequires evaluating multiple levels ofmaterial properties, pavement designs,and long term field performance.Currently, there are two studies that haveattempted to achieve such a goal usingtwo different approaches. These studiesare summarized below.Hicks and Scholz developed a life cyclecost analysis (LCCA) model to comparethe life cycle costs for HMA pavementswith and without lime [Hicks and Scholz(2003)]. The researchers surveyed tenstate DOTs and collected data on thefollowing topics: reasons for using lime inHMA mixtures, the cost of adding lime inHMA mixtures, and the field performanceof HMA mixtures. Table 19 presents thereasons identified by the various DOTs forthe use of Lime in HMA mixtures.Reducing stripping was the mostimportant attribute of using lime in HMAmixtures for all DOTs followed by alteringthe properties of fines. Improve agingresistance, stiffening the binder, andimprove fracture toughness were rankedas lower importance which may be adirect result of the lack of information onthe impact of lime on these properties.Table 20 lists typical costs of adding limeinto HMA mixtures in terms of the addedcost per ton of mix. The cost of addinglime does not significantly vary amonglocations, but it significantly variesbetween non-marinated and marinatedmixtures.The research developed a computerizedLCCA model that incorporates initial costs,maintenance costs, and salvage valuesalong with the performance of HMApavements with and without lime tocompare the effectiveness of adding lime.Table 21 summarizes the deterministicLCCA of HMA pavements with and withoutlime on interstates and state highways inthe ten surveyed states. The study was23

ased on data gathered from states thatuse lime to treat HMA mixtures withknown stripping problems. The LCCA datashowed that the antistripping benefits ofusing lime in HMA mixtures results in awide range of savings with anapproximate average saving of $2.00/yd 2 .This translates into an approximate savingof $20/ton of HMA mix which comparesvery favorably with the average additionalcosts of using lime of $1.25/ton for nonmarinatedand $4.00/ton for marinated(ranges are presented in Table 21).The researchers also conducted aprobabilistic LCCA of HMA pavements withand without lime. The probabilisticanalysis accounts for the inherentvariabilities in materials properties andcost and in the predicted fieldperformance. The probabilistic analysisshowed similar results to the deterministicanalysis with one additional finding: in 79to 96 percent of the time, the life cyclecosts of HMA pavements with lime are lessexpensive than the life cycle costs of HMApavements without lime. In other words,there is a 79 to 96 percent chance thatusing HMA mixtures with lime will be lessexpensive than using HMA mixtureswithout lime.Sebaaly and colleagues used theimpact of lime on the performance of HMAmixtures in the laboratory and in the fieldto predict the impact of lime on pavementlife [Sebaaly at al (2003)]. Lime treatedand untreated pavement sections weresampled, and their properties wereevaluated using laboratory tests.Pavement performance data from thepavement management system (PMS)were used to compare the fieldperformance of lime-treated anduntreated sections. Finally, the data fromthe laboratory evaluation of field sectionswere used in the AASHTO PavementDesign Guide to assess the impact of limeon the design life of flexible pavements inNevada.The laboratory portion of the researchconcluded that the lime treatment of24Nevada’s aggregates significantlyimproves the moisture resistance of HMAmixtures. The study showed the limetreatedHMA mixtures becomesignificantly more resistant to multiplefreeze-thaw cycles than do the untreatedmixtures. Lime-treated mixtures showedexcellent properties for locations in thewheelpath and between the wheelpaths,which indicates that lime treatment helpsHMA mixtures in resisting the combinedaction of environmental and trafficstresses.The field portion of the research used PMSdata to compare the field performance ofprojects that were constructed withuntreated and lime-treated mixtures. Thecommon feature among the projects thatwere compared is that they wereconstructed on the same highway facility,which implies that they received the sametraffic and environmental stresses. Theperformance of the projects wascompared in terms of their presentserviceability index (PSI) as developedfrom the AASHO Road Test. The PSI ispresented on a scale of 0 to 5 with 4.2rating representing a newly constructedflexible pavement and a PSI below 2.0indicating a rough road in need of majorrehabilitation. The performance of theuntreated versus lime-treated pavementswas evaluated using the following criteria:1. Comparison of the change inaverage PSI value,2. Comparison of the occurrence ofthe low PSI values, and3. Comparison of the impact of theoccurrence of the low PSI value onthe average PSI value.Criterion 1 represents the need to performmaintenance activities throughout theservice life of the pavement. Criterion 2represents the frequency of maintenanceactivities. Criterion 3 is introduced toassess whether the occurrence of a lowPSI is an isolated event or a predominantone. For example, if the occurrence of thelow PSI value did not affect the average

PSI, the low PSI value existed at anisolated milepost within the project, and itdid not represent the conditions of themajority of the project. However, if theoccurrence of the low PSI value affectedthe average PSI, the low PSI value existedon the majority of the mileposts within theproject. This concept is clearly shown inFigure 37, in which low PSI valuessignificantly affected the average PSI forthe untreated mixture. For the limetreatedmixture, low PSI values did notaffect the average PSI. This indicates thatthe low PSI value represented theconditions of the majority of the milepostsof the untreated mixtures, and the low PSIvalue on the lime-treated mixturesrepresented only an isolated milepostwithin the entire project.Table 22 summarizes the fieldperformance of the untreated and limetreatedmixtures in terms of the threeestablished criteria and on the basis of thePSI trends of the untreated and limetreatedsections. The data in Table 22were evaluated on the basis that a goodperformingpavement section would havenone to moderate reduction in theaverage PSI, none to moderateoccurrence of low PSI, and an insignificantimpact of the low PSI. Based on thepavement management system (PMS)data and the analysis summarized in Table22, the researchers concluded that thelime-treated mixtures performed betterthan the untreated mixtures under allthree criteria and for all the evaluatedprojects. From these findings, it wasconcluded that lime treatment of HMAmixtures in Nevada resulted in betterperformingHMA pavements.The last step in evaluating theperformance of lime in HMA mixtures wasto quantify its impact on the actualpavement life. To achieve this, theresearchers used the data from thelaboratory evaluation of the field projectsin the AASHTO Guide for Design ofPavement Structures in conjunction withthe following three assumptions:1. The sixth freeze-thaw cycle wasselected to represent the criticalstage for the damage of HMAmixtures.2. The percent reduction in theresilient modulus (Mr) isproportional to the percentreduction in the layer coefficient(a 1 ), except if the cores failed afterthe sixth freeze-thaw cycle, thenthe a 1 will be assigned a value of0.1.3. The reduced Mr exists during 4month of the year and theweighted a 1 will be used torepresent the relative strength ofthe HMA layer.Table 23 summarizes the data generatedfrom the structural design analysis. Thestep of converting the increase in theEquivalent Single Axle Loads (ESAL) intopavement life assumes that Nevada DOTexpects an 8-year life from untreated HMAmixtures, and therefore any percentageincrease in the ESALs due to limetreatment is directly converted into anincrease in pavement life over the 8-yearperiod.On the basis of the data generated fromthe AASHTO design guide analysis and thetrends shown by the PMS data, it wasconcluded that the lime treatment ofNevada’s HMA mixtures would increasethe pavement life by an average of 3years. This result represents an averageincrease of 38% in the expectedpavement life, which compares veryfavorably with the percent increase in thecost of HMA mixtures of 10% ($4/ton) dueto lime treatment of aggregates and the48-hours marination that is mandated bythe Nevada DOT.In 1995, the Texas DOT formed a jointindustry-TxDOT task group to identifyissues associated with the unsatisfactoryperformance of HMA pavements madewith crushed siliceous gravel aggregatesin northeast Texas [Tahmoressi and25

Scullion (2002)]. The task group madeseveral recommendations to improve theperformance of such pavements. One ofthese recommendations is to requireantistrip agent in all mixtures. As a resultof this recommendation, several HMApavements were constructed in northeastTexas with both liquid antistrip and limeadditives.In 2001, the task group evaluated theperformance of 38 HMA pavements innortheast Texas using both the Hamburgwheel tracking device and visualperformance surveys. Table 24summarizes the findings of the 2001evaluations. In this table the data isseparated into three groups [Tahmoressiand Scullion (2002)]. The first groupcontains all of the pavements that hadless than 5 mm rut depth. The secondgroup shows pavements with a rut depthof more than 5 mm, but less than 12.5mm. The third group contains all projectswith more than 12.5 mm rut depth. Atthe time of evaluation, TxDOT used amaximum allowable rut depth in theHamburg test of 12.5 mm.Tahmoressi and Scullion concluded: “Themajority of pavements in the first group(less than 5 mm rut depth) containedlime. Only two pavements with lime didnot fall in this group. These twopavements had 6.1 and 8.0 mm ofrutting, two of the better performers inthe second group. The pavements in thesecond group (rut depth between 5 and12.5 mm) displayed more distresses thanthe first group. The distresses weremostly of a cracking nature. Thepavements in the third group had thelowest average visual performance ratingof the three groups. Of the 18 projects inthis group, 15 used crushed siliceousgravel coarse aggregates. Half of thesepavements used liquid antistrippingadditives, and the other half did not useany additives. None of the sections thatused lime fell into this bottom group.”The conclusions of the TxDOT studyfurther support the findings of otherhighway agencies and researchers; thatlime treatment of aggregates improvesthe long term performance of HMApavements and increases their usefulservice life.METHODS USED TO ADD LIMETO HMALime can be added to HMA during theproduction process by a number ofdifferent methods. This review describescurrent field practices and presentsresearch evaluating their effectiveness. In2003, the NLA produced a report on howto add lime to HMA mixtures based on sitevisits in four states(http://www.Lime.org/howtoadd.pdf).Techniques used to add lime to HMArange from adding dry lime to the drummixer at the point of asphalt binder entryto adding lime to aggregate followed by“marination” for several days. Quicklimeshould not be added to HMA unless it firsthas been completely hydrated. Ifquicklime remains unhydrated in the HMA,it will change to Ca(OH)2 when it comesinto contact with water during the servicelife of the pavement. This reaction (i.e.,changing from CaO to Ca(OH)2) isexpansive and will create a volumechange in the HMA and losses in strengthand performance.Lime can be successfully proportioned andmixed in HMA in both batch and drummixers. In Georgia, dry lime is typicallyadded at the point in the drum mixerwhere the asphalt binder is introduced.Dry lime can be added to dry aggregateand to wet aggregate. Moisture levels inwet aggregate are typically about two tothree percent above the saturated surfacedried condition of the aggregate. Moistureionizes the lime and helps distribute it onthe aggregate surface. Lime-treatedaggregates can be stockpiled for26

“marination” or can be conveyed directlyto the drying and mixing portion of theHMA production unit.Lime slurries made from hydrated lime orquicklime have also been used. Limeslurriedaggregates are conveyed directlyto the drying and mixing portion of theHMA facility or placed into stockpiles formarination. The use of lime slurry hasseveral advantages: improved resistanceof the treated hot mix to stripping;reduced dusting associated with theaddition of dry lime to the aggregate; and,improved distribution of the lime on theaggregate. However, the use of limeslurries adds more water than is typicallyused for conventional lime applicationsand can substantially increase the watercontent of the aggregate prior to enteringthe drying and mixing portions of the HMAfacility. Increased fuel consumption andreduced HMA production can result. Theuse of lime slurries also requirespurchasing or renting specializedequipment to prepare the lime slurry atthe site of the mixing operation.Marinating or stockpiling treatedaggregate prior to re-entry into the HMAfacility is fairly common in California,Nevada, and Utah. The advantages ofmarination include: a reduction inmoisture content while the aggregate isstockpiled; the lime treatment can beperformed separately from the HMAproduction with some economicadvantage; and an improvement in theresistance to moisture can result(particularly when aggregates have clayspresent in their fines or have claycoatings). The treatment of aggregatesfollowed by marination also allows for theuse of the lime on only problematic orstrip-prone aggregate. For example, a fineaggregate may be highly water sensitivewhile coarse aggregates may not be watersensitive.Disadvantages of marination include:additional handling of the aggregate;additional space for both lime-treated anduntreated stockpiles; and lime can bewashed from the aggregate duringmarination. Carbonation of the lime instockpiles of aggregate does not appear tobe a major problem, as it usually occursonly on the surface of the stockpile.Adding dry lime to the asphalt binder andstoring the lime-modified binder prior tomixing with the aggregate has not beenpracticed in the field. However, recentresearch demonstrates the potentialeffectiveness of this approach [Lesueurand Little (1999)].LABORATORY AND FIELDSTUDIES ASSESSING METHODSOF LIME ADDITIONForming a mastic of a homogeneous blendof hydrated lime in bitumen has beenshown to provide substantial improvementin high temperature stiffness, lowtemperature toughness, rut resistance,and reduced hardening effects [Lesueurand Little (1999)]. Based on thesefindings and confirmation in other studies,research is currently underway toinvestigate additional ways of introducinghydrated lime into the HMA mixingprocess.ADDITION OF LIME IN THE HOTMIX OPERATIONUniversity of Nevada, RenoTwo studies, which were conducted by theUniversity of Nevada, simulated field limeaddition practices [Waite et al., (1986),and McCann and Sebaaly (2003)]. Figure38 shows the resilient modulus valuesbefore and after conditioning when testedusing the AASHTO T 283 method for HMAmixtures treated with different types oflime and different methods of application.The data from the study conducted byMcCann and Sebaaly summarized in Table17 indicate that, for the aggregates andbinders studied, the method of lime27

application does not affect the moisturesensitivity of the mix.Nevada DOTThe Nevada DOT conducted a study toevaluate the impact of lime applicationmethod on the properties of HMA mixtures[Epps Martin et al. (2003)]. The threeyears of data presented in Table 25 leadto the conclusion that, by requiringmarination, the percent of field mixturesfailing the retained strength ratio issignificantly reduced from a 3-yearaverage of 18 percent to 3 percent (Table25). It is believed that two reasons led tothis finding: a) marination during fieldoperations allows the contractor toconcentrate on treating the aggregates,because they are separated from the restof the mix production process; and b)marination improves the properties ofaggregates having plastic fines. NDOTalso evaluated the impact of marinationperiod on the moisture sensitivity of HMAmixtures. Table 26 summarizes themoisture sensitivity properties of HMAmixtures at various marination periods.The data from this study showed thatlonger marination times will not improvethe resistance of HMA mixtures tomoisture damage. In the majority of thecases, prolonging the marination timesignificantly reduced the retained strengthratio. Based on this finding, NDOTmandated a minimum of 48 hours and amaximum of 60 days of marination time.Utah DOTThe Utah Department of Transportationhas performed both AASHTO T 283 andimmersion compression tests onaggregates treated with lime by differentmethods [Betenson (1998)]. Thislaboratory research indicated that the useof marination produces higher retainedproperties than the use of dry lime ondamp or wet aggregate (see Figures 39 to42).Georgia DOTGeorgia DOT conducted a laboratory studyto determine the benefits of using lime dryor in slurry form [Collins (1988)]. Both dryand slurry addition methods providedbenefits to the aggregate-asphaltmixtures used (see Figure 43). Havingnoted only minor differences between thetwo methods of addition, Georgia DOTelected to add dry lime in drum mixersnear the asphalt binder feed line towardsthe end of the drum.Texas Hot Mix AsphaltPavement Association andTexas DOTThe Texas Department of Transportation(TxDOT) and the Texas Hot Mix AsphaltPavement Association conducted a fieldexperimental project to study variousmethods of adding lime to batch and drummixers [Button and Epps (1983)]. Tests atbatch mixers indicated that the use oflime slurry produced the best results,although dry lime added to dampaggregate was also beneficial (Figure 44).For drum mixers, the addition of lime tothe cold feed and to aggregates prior tostockpiling was effective (Figure 45). Theaddition of dry lime to the drum mixer,however, was not effective in this study--probably because special lime-additionequipment was not used for this field test.The benefits of stockpiling or marinationare also evident from these data.In 1999, TxDOT conducted a study toevaluate the effectiveness of the differentmethods of adding lime to HMA mixture[Tahmoressi and Mikhail (1999)]. Thestudy evaluated laboratory preparedmixtures under the Modified Lottman testand the Hamburg wheel tracking device.The Texas researchers concluded thatthere is no significant difference betweenthe different methods of adding lime onthe resistance of the HMA mix to moistureinduced damage (Figure 46). Theyrecommended that TxDOT allows the28

addition of dry lime to dry aggregates inthe mixing drum or pugmill prior toasphalt addition.ADDITION OF LIME TOSELECTED FRACTIONS OFSTOCKPILESOne of the benefits of adding lime tostockpiles of aggregates is the opportunityfor separate treatment of those aggregatefractions that are water susceptible. Asecondary benefit is the potential fortreating one aggregate fraction at a higherconcentration of lime and then introducingthe lime to the other aggregate fractionduring the HMA production process. Oneof the potential disadvantages ofpretreating and stockpiling theaggregates--carbonation of the hydratedlime--has not been found to be significant(see below).Texas DOTThe effectiveness of treating individualstockpiles was studied as part of theextensive field and laboratory programperformed by TxDOT and the Texas HotMix Asphalt Pavement Association [Button(1984)]. For one series of tests, limeslurry was added to only the fineaggregate fraction, to only the coarseaggregate fraction, and to the entireaggregate. All were held in stockpiles forup to 30 days. Hydrated lime was aneffective antistrip additive for all limeaddition methods (Figure 47). The lengthof time between mixing the lime withaggregate and mixing the treatedaggregate with an asphalt binder did notsignificantly change the effectiveness.In 1982, TxDOT performed a fieldresearch project to investigate theeffectiveness of pretreating only the sandfraction of an aggregate with lime (i.e.,the effectiveness of the lime beingtransferred from the fine aggregate to thecoarse aggregate) during the aggregateblending, drying, and mixing operations ata HMA production facility [Kennedy et al.,(1982) and (1983)]. The pretreatment ofthe sand fraction reduces the watersensitivity of the mixture (see Figure 48).(Stockpiling the lime-treated sand for aperiod of 28 weeks was not detrimental tothe effectiveness of the lime.) Sufficientlime was added to a moist sand toproduce lime concentrations in the totalaggregate that ranged from approximately0.3 to 1.5 percent by dry weight ofaggregate. Approximately 25 percent sandwas used to produce the HMA.Mississippi DOTThe Mississippi DOT pretreated a crushedgravel with a lime slurry in 1993 [Little(1994)]. Longer stockpile storage times(up to 90 days) produced mixes withacceptable characteristics. The asphaltmix contained 65 percent pretreatedgravel, 10 percent No. 8 limestone, 10percent agricultural limestone, 15 percentcoarse sand, and 5.8 percent asphaltbinder. Samples of the aggregate andasphalt binder were tested using AASHTOT 283 to determine water sensitivity aftervarious time periods of storage instockpiles (marination). (Over 11 inchesof rain fell during the stockpilingoperation.) Extended lime treatment isvery effective in reducing moisturesusceptibility (Figure 49).National Center for AsphaltTechnologyAn extensive study to investigate theeffectiveness of lime additions to only thefine aggregate fraction was performed in1993 by the National Center for AsphaltTechnology [Hansen et al., (1993)]. Threefine aggregates and a single coarseaggregate (a Georgia granite) were usedin the study. Twenty percent sand wasused in the mixtures, which were testedby the ASTM D 4867 and AASHTO T 283methods. Laboratory lime additiontechniques included lime slurry and dry29

lime added to a moist aggregate. Lime isan effective antistrip agent when added tothe fine aggregate fraction (Figure 50).Stockpile CarbonationThe lime carbonation (reaction with CO2to form CaCO3) that occurs in a limetreatedstockpile can potentially increasewater sensitivity because carbonated limeis unable to react with HMA or fines. Twostudies demonstrate that carbonation isgenerally not a problem. In 1993, TxDOTevaluated lime-treated field sand that hadbeen stockpiled for seven months [Little(1993)]. There was no evidence ofcarbonation or deterioration in limeconcentrations. Graves evaluatedcarbonation in lime-treated aggregates[Graves (1992)]. For up to 180 days,carbonation was minimal at depthsgreater than three inches (Figure 51).CONCLUSIONSIt has been proven through laboratory andfield testing that hydrated lime in HMAsubstantially reduces moisture sensitivity.Lime enhances the bitumen-aggregatebond and improves the resistance of thebitumen itself to water-induced damage.Recent surveys document the success andacceptance of lime in HMA throughout theUnited States.The ability of lime to improve theresistance of HMA mixtures to moisturedamage, reduce oxidative aging, improvemechanical properties, and improveresistance to fatigue and rutting, has ledto observed improvements in the fieldperformance of lime-treated HMApavements. Life cycle cost analyses haveshown that using lime results inapproximate saving of $20/ton of HMAmix while field performance data showedan increase of 38% in the expectedpavement life.Several highway agencies have proven theeffectiveness of lime with cold-in-placerecycled mixtures. Lime treatment of theCIR mixtures increased their initialstability which allows the early opening ofthe facility to traffic and it improves theirresistance to moisture damage whichsignificantly extended the useful life of thepavement.Laboratory and field performance studiesconducted over the last several yearsshows that hydrated lime improves therheology of the mastic and producesmultifunctional and synergistic benefits inthe mixture. Work in the United Statesand in Europe has proven that hydratedlime can substantially improve theresistance of the HMA to permanentdeformation damage at hightemperatures. Hydrated lime alsosubstantially improves low temperaturefracture toughness without reducing theability of the mastic to dissipate energythrough relaxation. Recent researchdemonstrates that hydrated lime is indeedan “active” filler that interacts with thebitumen; and some of the mechanismsresponsible have been identified. It hasbeen shown that there are high and lowtemperature rheological benefits in addinghydrated lime to the HMA mastic. It hasbeen proven that there are also benefitsof reduced susceptibility to age hardeningand improved moisture resistance. Clearlyhydrated lime is an attractivemultifunctional additive to HMA.Current tests to evaluate additives arebased solely on short-term retainedstrengths following moisture conditioning(e.g., AASHTO T 283). This does notrepresent long-term performance of anasphalt, which is influenced by factorsother than reduced moisture sensitivity(e.g., resistance to load-induced fatiguecracking or low temperature cracking).There is a pressing need for a simple andrepeatable test that can evaluate themultifunctional aspects of pavementperformance. Such a test will result insubstantial savings because it will more30

accurately identify those additives that arecapable of improving long-term asphaltpavement performance.Hydrated lime may be added in the HMAproduction process in several ways. Manydifferent methods have been usedsuccessfully. The experience of the statesand contractors currently dictates thepreferred manner of lime addition.Research activities are underway toinvestigate additional ways of addinghydrated lime at the HMA production site.Extensive laboratory and fieldperformance studies conducted over thepast few decades indicate that using limein HMA mixture will generate the followingproperties:1. Lime reduces stripping.2. It acts as a mineral filler to stiffenthe asphalt binder and HMA, whichreduces rutting.3. It improves resistance to fracturegrowth (i.e., improves fracturetoughness) at low temperatures.4. It reduces aging by favorablyaltering oxidation kinetics andinteracting with products ofoxidation to reduce theirdeleterious effects.5. It alters the plastic properties ofclay fines to improve moisturestability and durability.31

REFERENCES1. Aschenbrener, T. and Far, N., “Influenceof Compaction Temperature and Anti-Stripping Treatment on the Results fromthe Hamburg Wheel-Tracking Device,” Rpt# CDOT-DTD-R-94-9, ColoradoDepartment of Transportation, July 15,1994.2. Aschenbrener, T. “Survey on MoistureDamage of Hot Mix Asphalt Pavements,”Colorado DOT, Denver, CO, 2002.3. Bari J. and Witczak, M.W., “Evaluation ofthe Effect of Lime Modification on theDynamic Modulus Stiffness of Hot-MixAsphalt Use with the New Mechanistic-Empirical Pavement Design Guide,”Transportation Research Record No. 1929,pp. 10-19, 2005.4. Betenson, W.B., “Quality - The Word forthe 21st Century,” presentation atWorkshop on Lime in Hot Mix Asphalt,Sacramento, California, June 1998.5. Buttlar, W. G., Bozkurt, D., Al-Kateeb, G.G., and Waldhoff, A. S., “ UnderstandingAsphalt Mastic Behavior throughMicromechanics,” Paper Presented at theAnnual Meeting of the TransportationResearch Board, Washington, D.C., 1999.6. Button, J. W., Epps, J. A., “Evaluation ofMethods of Mixing Lime in AsphaltPavement Mixtures,” Texas Hot AsphaltPavement Association, July 1983.7. Button, J. W., “Use of Lime in AsphaltPavements,” Transportation Researcher,October 1984.8. Choquet, F. S., and Verhasselt, A., “Agingof Bitumens: from the Road to theLaboratory and Vice Versa,” Proceedingsof the Conference on SHRP and TrafficSafety on Two Continents, No. 1A, Part 3,pp. 194 - 213, 1994.9. Collins, R., “Status Report on the Use ofHydrated Lime in Asphaltic ConcreteMixtures in Georgia,” Georgia DOT,Materials and Research, June 13, 1988.10. Collins, R., Johnson, A., Wu, Y. and Lai, J.,“Evaluation of Moisture Susceptibility ofCompacted Asphalt Pavement Analyzer,”paper submitted to TRB, January 12-16,1997.11. Cross, S.A., “Experimental Cold In-PlaceRecycling with Hydrated Lime,”Transportation Research Record No. 1684,pp. 186-193, 1999.12. Epps, J. A., “Hydrated Lime in Hot Mix,”Presentation Manual, FHWA, AASHTO,NLA, 1992.3213. Epps Martin, A., Rand, D., Weitzel, D.,Sebaaly, P., Lane, L., Bressette, T.,Maupin, G.W., “Topic 7: Field Experience,”National Seminar on Moisture Sensitivityof Asphalt Pavements, February 4-6,2003, San Diego, CA, pp. 229-258.14. Fager, G.A., “Lime Slurry in Cold In PlaceRecycle,” Final Report to Kansas DOT,Topeka, Kansas, June 2004.15. Graves, R.E., “Lime in Sand for Hot MixAsphalt-Test Project Summary,” InternalMemorandum, Chemical Lime Group,December 1992.16. Hanson, D. I., Graves, R.E., and Brown, E.R., “Laboratory Evaluation of the Additionof Lime Treated Sand to Hot Mix Asphalt,”National Center for Asphalt Technology,Auburn University, 1993.17. Hopman, P.C., “Dutch Research on Fillersand Some Practical Consequences,”presented at the Lhoist Conference onLime in HMA, Brussels, Belgium, 1996.18. Hopman, P. C., “Hydroxide in Filler,”Netherlands Pavement Consultants,

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Slurry,” prepared for Chemical LimeCorporation, Texas TransportationInstitute, 1994.36. Little, D. N., “Stabilization of PavementSubgrades and Base Courses with Lime,”National Lime Association, Bulletin 333,1995.37. Little, D. N., “Hydrated Lime as a Multi-Functional Modifier for Asphalt Mixtures,”Presented at the HMA in Europe LhoistSymposium, Brussels, Belgium, October1996.38. Little, D. and Kim, Y. “Using DynamicMechanical Analysis as a Tool to Assessthe Suitable of Fillers in Asphalt MixturesBased on the Mastic Properties,”Proceeding of 10th Annual InternationalCenter for Aggregate ResearchSymposium, Baltimore, MD, 2002.39. Little, D.N. and Petersen, J.C., “UniqueEffects of Hydrated Lime Filler on thePerformance Related Properties of AsphaltCements: Physical and ChemicalInteractions Revisited,” Journal ofMaterials in Civil Engineering, Vol. 17, No.2, April 1, 2005.40. Lottman, R. P., “Predicting MoistureInduced Damage to Asphalt Concrete,”NCHRP Report 192, TransportationResearch Board, Washington, D.C., 1978.41. Lottman, R. P., “Predicting MoistureInduced Damage to Asphalt Concrete -Field Evaluation,” NCHRP Report 246,Transportation Research Board,Washington, D.C., 1982.42. Luxemburk, F., “The Experience with theUse of Hydrated Lime in Hot Mix Asphaltin Czech Republic,” Technical University,Prague, Czech Republic, Paper Presentedat Lhoist HMA Symposium, Dusseldorf,Germany, June 1998.43. Mallick, R.B., Pelland, R., and Hugo, F.,“Use of Accelerated Loading Equipment forDetermination of Long Term MoistureSusceptibility of Hot Mix Asphalt,” PaperPresented at the Annual Meeting of the34Transportation Research Board,Washington, D.C., January 2005.44. Mauget, G., “Foamed Bitumen: AnInnovative Technique for Binding Sandand Gravel,” Jean Lefevre Company, Metz,France, Paper Presented at Lhoist HMASymposium, Dusseldorf, Germany, June1998.45. Maupin, G.W. Jr. “Effectiveness ofAntistripping Additives in the Field,”Virginia Transportation Research Council,Report No. VTRC 96-R-5, September1995.46. Maupin, G.W. Jr. “Follow-up FieldInvestigation of the Effectiveness ofAntistripping Additives in Virginia,”Virginia Transportation Research Council,Report No. VTRC 97-TAR 6, January 1997.47. McCann, M. and Sebaaly, P.E., “Evaluationof Moisture Sensitivity and Performance ofLime in Hot-Mix Asphalt – ResilientModulus, Tensile Strength, and SimpleShear Tests,” Transportation ResearchRecord No. 1832, pp. 9-16, 2003.48. National Lime Association, “Evaluation ofStructural Properties of Lime StabilizedSoils and Aggregates (Volumes 1 & 2),”1999 (http://www.lime.org/SOIL.PDF).49. Petersen, J.C., Plancher, H., andHarnsberger, P.M., “Lime Treatment ofAsphalt to Reduce Age Hardening andImprove Flow Properties,” AAPT, Volume56, 1987.50. Radenberg, M., “Effect of Hydrated LimeAddition on the Deformation of Hot MixAsphalt in the Wheel Tracking Test,” IFTA,Essen, Germany, Paper Presented atLhoist HMA Symposium, Dusseldorf,Germany, June 1998.51. Recasens, R.M., Martinez, A., Jimenez,F.P., and Bianchetto, H., “Effect of Filleron the Aging Potential of AsphaltMixtures,” Transportation Research RecordNo. 1901, pp. 10-17, 2005.

52. Sebaaly, P.E. Hitti, E., and Weitzel, D.“Effectiveness of Lime in Hot-Mix AsphaltPavements,” Journal of theTransportation Research Board, No. 1832,TRB, National Research Council,Washington, D.C., 2003, pp. 34-41.53. Sebaaly, P.E., Tohme, P., Hitti, E.,Stansburry, K., and Epps, J., “AsphaltConcrete Anti-stripping Techniques,”South Dakota DOT Study SD99-10, FinalReport, Pierre, SD, 2003.54. Sebaaly, P.E., Bazi, G., Hitti, E., Weitzel,and Bemanian, S., “Performance of ColdIn-Place Recycling in Nevada,” Journal ofthe Transportation Research Board, No.1896, TRB, National Research Council,Washington, D.C., 2004, pp. 162-169.55. Sebaaly, P.E., Little, D., and Berger, E.“Idaho Transportation Department – SH67– Report of Test Results” ReportSubmitted To Idaho DOT by the ChemicalLime Company, June 2005.56. Si, Z., Little, D.N., and Lytton, R.L.,“Evaluation of Fatigue Healing Effect ofAsphalt Concrete by Pseudo Stiffness,”Presented at the Annual TransportationResearch Board, January 2002,Washington D.C.57. Tahmoressi, M., “Effects of Hydrated Limeon Hamburg Properties of LimestoneMixtures,” Research Report, PaveTexEngineering and Testing, Inc., 2002.58. Tahmoressi, M. and Mikhail, M.,“Evaluation of Methods of Adding Lime toHot Mix,” TxDOT, Bituminous Branch,1999.59. Tahmoressi, M., and Scullion, T., “AFollow-Up Evaluation of Hot-Mix PavementPerformance in Northeast Texas,” TxDOTProject 0-4104, Report 4104-1, 2002.60. Tayebali, A.A. and Shidhore, A.V., “Use ofLime as Antistrip Additive for MitigatingMoisture Susceptibility of Asphalt MixesContaining Baghouse Fines,” NorthCarolina DOT Project HWY 2005-15, 2005.61. Tarrer, Ray, “Use of Hydrated Lime toReduce Hardening and Stripping inAsphalt Mixes,” 4th Annual ICARSymposium, Atlanta, Georgia, 1996.62. Tunnicliff, D.G. and Root, R.,“Antistripping Additives in AsphaltConcrete - State of the Art,” Proceedings,Association of Asphalt PavingTechnologist, Vol. 51, Technical Sessions,Kansas City, Missouri, 1982.63. Vanelstraete, A. and Verhasselt, A.,“Effects of Hydrated Lime on theRheological Properties of Mastics Beforeand After Aging and on the Behavior andConstruction Aging of Mastics,” RoadResearch Center, Brussels, Belgium, PaperPresented at Lhoist HMA Symposium,Dusseldorf, Germany, June 1998.64. Verhasselt, A. and F.S. Choquet,“Comparing Field and Laboratory Aging ofBitumens on a Kinetic Basis,”Transportation Research Record No. 1391,pp. 30-38, 1993.65. Verhasselt, A., “Use of Lime in Hot MixAsphalt in Belgium,” presented at theLhoist Conference on Lime in HMA,Brussels, Belgium, 1996.66. Waite, H., Gardiner-Stroup, M., Epps, J.A., “The Effects of Various Lime Productson the Moisture Susceptibility of AsphaltConcrete Mixtures,” Department of CivilEngineering, University of Nevada-Reno,March 1986.67. Watson, D., “Status Report on the Use ofHydrated Lime in Asphaltic ConcreteMixtures in Georgia,” Georgia DOT,Materials and Research, June 9, 1992.68. Western Research Institute, “FundamentalProperties of Asphalt and ModifiedAsphalt,” Draft Final Report for the FHA,DTFH61-92C-00170, 1997.35

Table 1.Relative Behavior of Lime and Liquid Antistrip Additives in Georgia[Collins (1988)].TypeTensile Strength, 77 o F, psiMix Treatment Stability Flow Unconditioned Conditioned Ratio (%)BaseBEFGHLime 2777 10.9 94.6 88.7 93.8Liquid Additive 2515 10.8 89.2 78.6 88.1Lime 2685 10.6 91.2 87.3 95.7Liquid Additive 2380 11.1 91.6 79.7 87.0Lime 2616 10.4 92.9 87.9 94.6Liquid Additive 2315 10.8 94.0 78.2 83.2Lime 2487 10.4 89.9 88.0 97.9Liquid Additive 2392 11.6 85.1 73.5 86.4Lime 2247 10.3 103.0 102.4 99.1Liquid Additive 2109 10.0 101.1 80.4 79.5Lime 2325 11.0 104.0 85.5 82.2Liquid Additive 2272 10.7 86.7 74.4 85.8Table 2.Deformation (mm) After 20,000 Passes for Samples Treated with Various Anti-Stripping Treatments in Colorado [Aschebrener and Far (1994)].NoTreatment1 % Additive “A”Additive “B”HydratedLime Type 1 Type 2 Type 1 Type 2Mix 1 (17.0) 1 1.4 2.2 3.1 6.3 7.4Mix 2 (>20) 2.3 8.1 8.4 5.3 (14.6)Mix 3 (>20) 2.5 (13.7) 8.5 (>20) (12.4)Mix 4 8.7 2.3 6.2 4.7 5.0 4.31 Parentheses indicates that the mixture failed due to excessive deformation.36

Table 4.Recommended Binder Contents for Optimum Durability of HMA Mixtures[Ishai and Craus (1996)].Surface Activities of the Fillers BinderRate of FillerActivityExamples ofFillersHeat ofAdsorption(cal/gr).10 -2Spec Heat ofAdsorption(cal/m 2 )Content forOptimumDurabilityHigh Hydrated Lime >30 >0.55 ω optIntermediate LimestoneDolomite8 – 30 0.30 – 0.55 ω opt + 0.5%SandstoneLow Basalt

Table 6.TreatmentNoneHydratedLimeTensile Strength Properties of Untreated and Lime Treated Mixtures on the LoganInternational Airport [Mallick et al. (2005)].PropertyAggregate/MixtureA B CTS of Unconditioned mix (kPa) 807 1025 925TS after MMLS3 Loading (kPa) 649 954 727TS after 1 FT Cycle (kPa) 800 950 750TS after 10 FT Cycles (kPa) 633 586 334TSR after MMLS3 (%) 80 93 79TSR after 1 FT Cycle (%) 99 93 81TSR after 10 FT Cycles (%) 78 57 36TS of Unconditioned mix (kPa) 1001 1177 761TS after MMLS3 Loading (kPa) 1334 1381 1343TS after 1 FT Cycle (kPa) 960 1010 800TS after 10 FT Cycles (kPa) 979 1126 530TSR after MMLS3 (%) 133 117 176TSR after 1 FT Cycle (%) 96 86 105TSR after 10 FT Cycles (%) 98 96 70Table 7.Impact of Multiple Freeze-thaw Cycling on the Rutting Potential of Liquid andLime Mixtures from the Idaho SH67 Project [Sebaaly et al. (2005)].Increase in Potential for Rutting at .5 million ESALsF-T Cycles(%)Liquid MixLime Mix0 na na3 0 06 3 09 55 012 40 1018 150 5521 220 6539

Table 8.Mechanical Properties of Lime and Liquid Mixtures from the Idaho SH67 Project[Sebaaly et al. (2005)].MixtureMoistureConditioningDynamic Modulusin Compression,10 rad/sec, ksi, 25CDynamicModulus inTension, 10rad/sec, ksi, 25CRate ofDynamic Creep,(microns/cycle),25CLime Unconditioned 964 374 0.46Mix Conditioned 726 301 0.57Liquid Unconditioned 712 294 0.48Mix Conditioned 539 205 0.64Table 9.Plastic Shear Strains at 5,000 Cycles and Corresponding Rut Depth of NorthCarolina Mixtures, 50 o C [Tayebali and Shidhore (2005)].Type of Mix Lime Plastic Shear Strain (%) Estimated Rut Depth (in)Bone BHF % % Dry Wet Dry Wet1.5 0 1.86 2.00 0.20 0.226.5 0 1.42 1.78 0.16 0.205.5 1 1.33 1.40 0.15 0.15Enka BHF %1.5 0 1.55 1.78 0.17 0.206.5 0 1.71 1.61 0.19 0.185.5 1 1.33 1.37 0.15 0.1540

Table 10.Number of Cycles Corresponding to 7.5 mm and 5.0 mm Rutting in SpecimensTested by ASTEC Asphalt Pavement Tester [Collins et al. (1997)].Specimens with LimeSpecimens without LimeAggregate Vacuum Saturation Freeze-Thaw Vacuum Saturation Freeze-ThawSource 1 7803 c (2240) d 5000 (1467) 1748 (5000) 5609 (2166)Source 2 3685 (1303) 5242 (1796) 3310 (1177) 3507 (931)Source 3 2974 (1065) 2332 (680) 1805 (736) 452 (302)Source 4 2496 (734) 4240 (1242) 1983 (732) 2045 (579)c The first figure is the number of cycles corresponding to 7.5 mm failure criteriad The figure in parentheses is the number of cycles corresponding to 5.0 mm failure criteriaTable 11.Summary of Creep Test Data Evaluated According to the Procedure Developedby Little et al. (1994).1-Hour Strain, in./in., , p1-Hour Creep Modulus,E c , psiProperties of Steady State Region ofCreep CurveFrom Test Criterion From Test Criterion From Test CriterionTertiaryCreepC1 1 0.020 Failure -- Failure -- -- YesC2 0.009 HRS 3 2,200 HRS 0.40 HRS YesC3 Failure -- -- -- -- -- --L1 2 0.0018 HRR 4 10,500 HRR 0.20 HRR NoL2 0.052 MRR 5 3,750 MRR 0.25 MRR NoL3 0.0032 HRR 6,110 HRR 0.20 HRR No1 - C1 - Control sample 1 - mixture without lime2 - LI - Lime -treated sample 13 - HRS - High rut susceptibility4 - HRR - High rut resistance5 - MRR - Moderate rut resistance41

Table 12.Comparison of High Temperature Properties of the Un-aged and Aged Binders[Petersen et al. (1987)]Asphalt Treatment G*, 60C,10rad/sec, kPaPhaseAngle (deg)Viscosity,60C, PAgingIndex*None 1.33 84.6 838Un-agedBoscan20%Limestone20% HL2.303.2083.983.414502020Un-aged None 1.85 85.6 1170West TexasMaya blend20%Limestone20% HL2.562.6085.386.416101640None 2.25 72.1 179000 214AgedBoscan20%Limestone20% HL5.460.6869.082.14330005400029927Aged None 4.99 70.3 396000 338West TexasMaya blend20%Limestone20% HL1.461.0766.582.511600008490072052* Ratio of aged binder viscosity over un-aged binder viscosityTable 13.Comparison of Low Temperature Properties of the Aged Binders[Petersen et al. (1987)].Asphalt Treatment Temperature(C)Elongation(%)TensileStress (kPa)Modulus(kPa) x 10 4None-5 10.6 560 2.24-10 4.8 830 3.68Boscan 20%-5 4.0 1,000 6.19Limestone -10 2.8 1,680 11.320% HL-5 15+ 680 2.06-10 11.7 1,170 4.37None-5 5.5 650 3.24-10 4.4 1,340 4.89West Texas 20%-5 4.0 1,580 8.74Maya blend Limestone -10 0.75 1,310 15.620% HL-5 13.0 920 4.06-10 8.3 2,170 6.1242

Table 14.PropertyPenetration(0.1 mm)Viscosity@60 o C (P)Viscosity@135 o C (P)SofteningPoint (C)Impact of Hydrated Lime on the Properties of the Recovered Aged Binder fromHMA Mixtures in Spain [Rescasens et al. (2005)].0-days oven aging @80 o C2-days oven aging @80 o C7-days oven aging @80 o CNone HL None HL None HL78 79 43 47 34 371900 1600 4800 3700 6300 49003.9 4.2 5.2 6.1 7.6 6.251 48 57 53 62 55Table 15. Mix Design Properties of the Nevada CIR Mixtures [Sebaaly et al. (2004)].Project Emulsion EmulsionContent(%)US-50US-95NV-396ERA-25CMS-2SERA-75ERA-25CMS-2SERA-75ERA-25CMS-2SNo LimeUnconditionedMr at 77 o F (ksi)Mr Ratio*(%)1.5% LimeUnconditionedMr at 77 o F (ksi)Mr Ratio*(%)0.8 83 18 236 1001.3 58 32 209 1001.8 40 100 189 900.8 162 98 261 1001.3 98 100 204 1001.8 70 100 126 1000.8 134 52 262 1001.3 64 49 164 1001.8 60 35 165 1001.7 394 95 547 1002.2 383 67 377 1002.7 237 85 242 1001.7 589 60 641 1002.2 399 100 485 1002.7 429 66 373 1001.7 425 100 652 1002.2 543 100 716 1002.7 497 87 707 661.2 168 26 635 1001.7 130 37 571 892.2 82 45 441 1001.2 413 5 621 671.7 319 7 523 892.2 308 15 495 1001.2 318 16 484 1001.7 260 34 521 100ERA-752.2 205 54 430 100* Mr ratio = Mr at 77 o F conditioned samples x 100Mr at 77 o F unconditioned samples43

Table 16.Impact of Hydrated Lime on the Torsional Fatigue Life of Sand Asphalt Mixtures[Little and Kim (2002)].Binder: AAD-1Binder: AAM-1Strain(%)Neat LimestoneFillerHydrated LimeFillerNeat Hydrated LimeFiller0.2 34,555 a 65,610 (90) b NA 20,660 36,210 (75)0.28 10,060 18,843 (87) 45,960 (357) 4,510 11,235 (150)0.40 3,860 7,577 (96) 13,110 (240) 2,110 4,210 (100)a: average number of loading cycles until fatigue failureb: percent increase in fatigue life compared to unfilled mixTable 17.Impact of Lime Treatment and Lime Application Methods on the MechanicalProperties of Nevada’s HMA Mixtures [McCann and Sebaaly (2003)].PropertyResilientModulusTensileStrengthPermanentShear StrainNo-Lime vs. Lime Treated MixturesNone11 out of 12NOT DIFFERENT8 out 12NOT DIFFERENT7 out of 12NOT DIFFERENTConditioningOne Freezethawcycle9 out of 12DIFFERENT11 out 12DIFFERENT12 out of 12DIFFERENT18 Freezethawcycles12 out 12DIFFERENT12 out of 12DIFFERENT12 out of 12DIFFERENTLime ApplicationMethodOne and 18 freezethawcycles30 out 36NOT DIFFERENT31 out 36NOT DIFFERENT36 out of 36NOT DIFFERENTTable 18. Ratio of E* with Lime to E* without Lime [Witczak and Bari (2004)].Temperature Hydrated Lime Content (percent of dry weight of aggregate)(F) 1.0 1.5 2.0 2.5 3.014 1.24 1.07 1.31 1.33 1.3440 1.12 1.10 1.21 1.43 1.2270 1.26 1.31 1.06 1.91 1.31100 1.21 1.51 1.15 1.39 1.30130 1.24 1.09 1.14 1.45 1.25Average 1.21 1.22 1.17 1.50 1.28STD 0.06 0.19 0.09 0.23 0.05CV 5 16 8 15 444

Table 19. Reasons for Using Lime in HMA Pavements [Hicks and Scholz (2003)].AgencyResistStrippingImproveAgingResistanceStiffenBinderImproveFractureToughnessAlterProperties ofFinesArizona 1 3 2 3 2California – Dist 2 1 2 3 1 1Colorado 1 3 3 3 1Georgia 1 3 3 3 3Mississippi 1 1 2 - 3Nevada 1 3 3 2 1Oregon 1 2 3 3 3South Carolina 1 2 2 2 2Texas 1 3 2 3 2Utah 1 2 2 2 2Level of Importance:1 = very important2 = moderately important3 = less importantTable 20.Typical Costs for Adding Lime into HMA Mixtures based on Contractor Surveys[Hicks and Scholz (2003)].Agency Contractor Method Used % Lime Used Added Cost$/Ton-MixArizona FNF Non-Marinated 1.0 1.00Kiewit-Pacific Non-Marinated 1.0 1.00 – 1.50California FNF Marinated 0.7 – 1.2 3.75 – 4.25Granite Marinated 0.7 – 1.2 4.00 – 4.50Kiewit-Pacific Marinated 0.7 – 1.2 4.00Colorado Lafarge Non-Marinated 1.0 1.00 – 1.25Georgia APAC Non-Marinated 1.0 1.25 – 1.50Mississippi APAC Non-Marinated 1.0 1.25 – 1.50FNFNon-Marinated 1.5 1.00 – 1.50NevadaMarinated 1.5 3.75 – 4.25Granite Non-Marinated 1.5 1.25 – 1.50Marinated 1.5 2.75 – 4.50Oregon Kiewit-Pacific Non-Marinated 1.0 1.25 – 1.50Morse Brothers Non-Marinated 1.0 1.25 – 1.50South Carolina APAC Non-Marinated 1.0 1.25 – 1.50TexasAPAC Non-Marinated 1.0 – 1.5 1.00 – 1.50F.M. Young Non-Marinated 1.0 – 1.5 1.00 – 1.50Utah Granite Non-Marinated 1.0 – 1.5 1.25 – 1.50Staker Non-Marinated 1.0 – 1.5 1.25 – 1.5045

Table 21.Summary of the Life Cycle Cost Analysis of HMA Pavements with and withoutLime based on the Deterministic Approach [Hicks and Scholz (2003)].AgencyLife Cycle Cost, $/yd 2(Net Present Value)Savings Associated with UsingLimeLime-Treated Non-Treated $/yd 2 $/lane-mileAlternative Alternativea) InterstatesArizona 14.18 15.34 1.16 8,188California 24.83 28.25 3.42 24,075Colorado 20.52 24.51 3.99 28,067Georgia 20.65 24.79** 4.14 29,155Mississippi 7.65 9.05** 1.40 9,897Nevada 11.48 19.69*** 8.21 57,775Oregon 12.34 13.91 1.57 11,019South Carolina 20.90 21.53** 0.63 4,421Texas 8.40 8.11 0.29 2,100Utah 17.30 22.92*** 5.62 39,530b) State/Federal Lands HighwaysArizona 5.37 7.61 2.24 15,769California 24.18 27.45 3.27 23,018Colorado 9.47 10.50 1.03 7,256FHWA 7.69* 8.01* 0.32 2,297Georgia 7.71 9.28** 1.57 11,093Mississippi 7.20 7.74** 0.54 3,786Nevada 10.01 10.92*** 0.91 6,426Oregon 11.68 14.59 2.91 20,519South Carolina 21.71 25.96** 4.25 29,958Texas 9.03 9.60 0.57 3,974Utah 15.99 18.81*** 2.82 19,904* Federal Lands Highways only.** Not used by agency; life of non-lime alternative to be 2 years less than lime-treated alternative.*** Not used by agency, but agency estimated relative life of non-lime alternative.46

Table 22.Summary of the Performance of Field Projects based on Pavement ManagementSystem [Sebaaly et al. (2003)].StateRegionSouth:LasVegasAreaNorth:RenoAreaRoute Mixture Year ofConst.I-15 Untreated 1984I-15Lime-TreatedReductionin PSIModerate(after 4 th year)Occurrenceof low PSIFrequentImpact of LowPSIInsignificant1992 None None InsignificantUS-95 Untreated 1986 Severe Frequent SignificantUS-95Lime-TreatedI-80 Untreated 1983I-80Lime-Treated1996 None Infrequent Insignificant1990I-80 Untreated 1984I-80Lime-TreatedSevere(years 3, 5, 6)Moderate(years 3 and 6)Moderate(years 2 and 5)FrequentModerateFrequentSignificantInsignificantSignificant1994 None Frequent InsignificantTable 23.Impact of Lime Treatment on Pavement Life in Nevada based on AASHTODesign Guide [Sebaaly et al. (2003)].ProjectPecos-untreatedUS-95-treatedRussell-untreatedSunset-treatedSR-599-treatedPlumas-untreatedGreens-UntreatedSR-516-treatedMr (ksi)Uncond. 6 thCycle1900 1041100 4601900 2701050 1931250 345970910170000383Reduceda 10.020.150.050.070.100.010.010.08Weighteda 10.240.280.250.260.270.230.230.26SN3.443.743.543.603.643.443.443.64ESALsMillionsIncreasein ESALsIncrease inPav. Life(%)1.8503.120 70 6**2.2102.415 14* 12.6001.8501.8502.60040 3* Average percent increase in ESALs for the two lime-treated projects as compared with the untreated project.** Increase in pavement life is based on an average of 8-year life for untreated projects.47

Table 24.Performance of HMA Pavements in Northeast Texas based on Hamburg RutDepth and Visual Performance Rating [Tahmoressi and Scullion (2002)].ProjectLayerHamburgRut Depth (mm)@20,000 cyclesAge(years)VisualPerformanceRatingAntistripAgentCoarseAggregateMineralogyScreeningMineralogyAtlanta – 4 1 0.6 6 100 Lime Gravel GravelAtlanta – 9 1 0.6 5 100 Liquid Limestone LimestoneAtlanta – 8 1 1.0 5 100 Liquid Sandstone SandstoneAtlanta – 14 1 1.3 4 95 Lime Gravel GravelAtlanta – 16 1 1.3 4 55 Lime Sandstone SandstoneAtlanta – 11 1 1.8 5 95 Lime Igneous IgneousAtlanta – 2 1 2.1 6 70 Lime Gravel GravelAtlanta – 12 1 2.5 4 95 Lime Gravel GravelAtlanta – 15 1 3.0 4 100 Liquid Sandstone SandstoneAtlanta – 3 1 4.7 6 65 Liquid Sandstone SandstoneAtlanta – 13 1 4.8 4 85 Lime Gravel GravelAverage 2.2 4.8 87.3Tyler – 3 1 6.1 4 95 Lime Gravel LimestoneLufkin – 8 1 6.2 5 85 Liquid Gravel LimestoneAtlanta – 10 1 8.0 5 70 Lime Quartzite QuartziteTyler – 6 1 8.0 6 95 Liquid Limestone LimestoneAtlanta – 1 1 8.1 7 70 Liquid Gravel GravelAtlanta – 5 1 8.9 5 100 Liquid Limestone LimestoneTyler – 4 1 10.3 9 65 None Sandstone SandstoneLufkin – 3 2 10.5 5 70 None Limestone LimestoneAtlanta – 18 2 11.2 5 70 Liquid Gravel GravelAverage 8.6 5.7 80.0Tyler – 5 1 13.0 12 70 None Limestone LimestoneAtlanta – 17 2 13.9 6 65 Liquid Limestone LimestoneLufkin – 6 1 15.8 8 55 None Gravel LimestoneAtlanta – 6 1 16.6 6 80 Liquid Gravel GravelLufkin – 5 1 18.2 10 70 None Gravel LimestoneAtlanta – 7 1 18.5 7 70 Liquid Gravel GravelTyler – 1 1 19.2 8 100 Liquid Gravel LimestoneLufkin – 2 1 20.5 10 85 None Gravel LimestoneTyler – 7 1 36.2 6 40 Liquid Igneous IgneousLufkin – 4 1 43.9 4 40 Liquid Gravel LimestoneTyler – 2 1 56.8 8 90 Liquid Gravel GravelLufkin – 3 1 59.5 5 70 None Limestone LimestoneLufkin – 8 2 83.3 6 85 Liquid Gravel LimestoneTyler – 8 1 9 70 Liquid Gravel GravelLufkin – 1 2 9 50 None Gravel LimestoneLufkin – 7 1 7 40 None Gravel LimestoneTyler – 9 1 9 55 None Gravel LimestoneLufkin – 1 1 8 50 None Gravel LimestoneAverage 32.0 7.7 65.848

Table 25.Nevada DOT Moisture Sensitivity Data of 97-99 HMA Mixtures[Epps Martin et al. (2003)].Mix DesignField MixturesPropertyMarinated Non-marinated Marinated Non-marinated97 98 99 97 98 99 97 98 99 97 98 99No. of samples 39 80 70 28 13 7 118 312 370 114 95 61Uncond. Tensilestrength, psi 1 101 87 99 122 121 140 94 88 97 118 143 131Fail @ 65 psi, % 0 14 0 0 0 0 12 9 1 2 0 0Strength Ratio, % 2 84 90 94 81 84 86 89 90 94 76 82 81Fail @ 70% 13 1.3 1.4 25 15 0 3.4 2.2 3.8 30 16 81 Average unconditioned tensile strength.2 average retained strength ratioTable 26.Agg.SourceLockwoodDaytonLone MtnSuzieCreekNDOT Moisture Sensitivity Properties of HMA Mixtures at Various MarinationTimes [Epps Martin et al. (2003)].Binder 48 hours 45 days 60 days 120 daysGrade Strength Ratio Strength Ratio Strength Ratio Strength RatioAC-20 107 88 138 40 146 30 139 43AC-20P 75 85 101 38 72 46 96 50PG64-28 70 74 101 36 93 47 110 61AC-20 115 96 138 62 110 61 109 79AC-20P 82 95 85 70 75 63 91 75PG64-28 79 93 107 66 88 66 91 65AC-20 164 91 142 96 138 100 143 97AC-20P 124 103 133 91 120 100 116 96PG64-28 100 90 127 63 104 68 92 69AC-20 82 85 88 70 90 76 116 44AC-20P 52 133 60 89 67 74 62 66PG64-28 62 111 74 96 71 70 87 3049

Did not respondMoisture DamageNo Moisture DamageFigure 1. Extent of Moisture Damage in the United States [Hicks (1991)].Did not respondNo Moisture Damage0-10%10-20%20-30%30-40%Figure 2.Percentage of Pavements Experiencing Moisture Related Distress by State[Hicks (1991)].50

Do You Treat HMA for Moisture Damage?PredominantType of TreatmentUsedLimeLime or liquidsLiquidsLiquids seldomNo or very rarelyFigure 3. Distribution of Moisture Damage Treatments [Aschenbrener (2002)].250Resilient Modulus 25C,ksi200150100500Mix A Mix B Mix C Mix D Mix EMix TypeVacuum Vac + F/T Low Vac. + F/TFigure 4. Effect of Freeze-Thaw on Resilient Modulus [Epps et al. (1992)].51

Retained Tensile Strength, %1401201008060402001 2 3 4 5 6 7 8 9Number of Freeze- Thaw CylesNo Additive Pavebond LP Lime Slurry DowFigure 5.Effect of the Number of Freeze-Thaw Cycles on Retained Tensile Strength forVarious Additives [Epps et al. (1992)].Retained Tensile Strength, %12010080604020020 30 40 50 60 70 80 90 100Saturation, %Figure 6.Effect of Degree of Saturation on the Tensile Strength Ratio[Kennedy and Ping (1991)].52

Effectiveness Rating9876543210AASHTOT165(11*)AASHTOT182(3*)AASHTOT283(7*)Modulus Ratio(1*)Boil Test (8*)TensileStrengthRatio, TSR(7*)Mixture TestMeanStd. Dev* Note: numbers in parentheses represent number of responses.Figure 7.Relative Effectiveness of Mixture Tests Procedures to IdentifyMoisture-Related Problems [Hicks (1991)].Do You Test for Moisture Susceptibility?Type of TestTensileCompressiveRetained StabilityHamburg &TensileNoneFigure 8.Type of Tests used to Assess Moisture Susceptibility of HMA Mixtures[Aschenbrener (2002)].53

When Do You Test for Moisture Susceptibility?Time of TestingMix DesignMix Design &Field AcceptanceNoneFigure 9.Testing Stage for Moisture Susceptibility of HMA Mixtures[Aschenbrener (2002)].Cycles to Failure2520151050A B C D E F G HAdditive TypeControl Liquid Lime PyridineFigure 10. Effect of Selected Modifiers on Moisture Damage as Measured by the Freeze-Thaw Pedestal Test [Kennedy and Ping (1991)].54

140120100Ratio, %806040200No Additive 1% PC BA 2000 1% Lime SlurryAdditiveMR RatioTS RatioFigure 11. Effect of Various Additives on the Retained Strength (Following LottmanConditioning) of Asphalt Mixtures with 6.0% Asphalt Cement [Epps (1992)].55

Tensile Strength Ratio (TSR), %DISTRICT 17 - RIVER GRAVEL AGGREGATELaboratory Mixture17016015014013012011010090807060504030201000 1 2 3 4 5 6 7 8 9 10Number of Freeze-Thaw CyclesTensile Strength Ratio (TSR), %DISTRICT 16 - LIMESTONE AGGREGATELaboratory Mixture17016015014013012011010090807060504030201000 1 2 3 4 5 6 7 8 9 10Number of Freeze-Thaw CyclesLIME SLURRY BA3000 PERMA-TAC NO ADDITIVELIME SLURRY AQUA-SHIELD PAVEBOND LPDOWNO ADDITIVETensile Strength Ratio (TSR), %DISTRICT 13 - CRUSHED GRAVEL AGGREGATELaboratory Mixture17016015014013012011010090807060504030201000 1 2 3 4 5 6 7 8 9 10Number of Freeze-Thaw CyclesLIME SLURRY BA2000 PERMA-TAC PLUS NO ADDITIVETensile Strength Ratio (TSR), %DISTRICT 6 - FHYOLITE AGGREGATELaboratory Mixture17016015014013012011010090807060504030201000 1 2 3 4 5 6 7 8 9 10Number of Freeze-Thaw CyclesLIME SLURRY UNICHEM PERMA-TACPAVEBOND LPNO ADDITIVEFigure 12.Multiple Freeze-Thaw Cyclic Tests Results for Laboratory Mixtures ComparingSeverity of Tests Method on the Ability to Differentiate Between Lime and OtherAnti-Strip Additives [Kennedy and Ping (1991)]. (continued on next page)56

Tensile Strength Ratio (TSR), %DISTRICT 25 - CRUSHED GRAVEL AGGREGATELaboratory Mixture17016015014013012011010090807060504030201000 1 2 3 4 5 6 7 8 9 10Number of Freeze-Thaw CyclesLIME SLURRY AQUASHIELD II FINA-APERMA-TAC UNICHEM NO ADDITIVETensile Strength Ratio (TSR), %DISTRICT 1 - CRUSHED SANDSTONE AGGREGATELaboratory Mixture17016015014013012011010090807060504030201000 1 2 3 4 5 6 7 8 9 10Number of Freeze-Thaw CyclesLIME SLURRY ARR-MAZ DOWFINA-A INDULIN AS-1 PAVEBOND SPECIALPERMA-TAX PLUS NO ADDITIVETensile Strength Ratio (TSR), %DISTRICT 19 - CRUSHED GRAVEL AGGREGATELaboratory Mixture17016015014013012011010090807060504030201000 1 2 3 4 5 6 7 8 9 10Number of Freeze-Thaw CyclesLIME SLURRY ARR-MAZ AQUASHIELD IIBA 2000 PERMA-TAC NO ADDITIVETensile Strength Ratio (TSR), %DISTRICT 21 - CRUSHED GRAVEL AGGREGATELaboratory Mixture17016015014013012011010090807060504030201000 1 2 3 4 5 6 7 8 9 10Number of Freeze-Thaw CyclesLIME SLURRY ARR-MAX AQUASHIELD IIDOW FINA-B PAVEBOND LPPERMA-TACNO ADDITIVEFigure 12.Multiple Freeze-Thaw Cyclic Tests Results for Laboratory Mixtures ComparingSeverity of Tests Method on the Ability to Differentiate Between Lime and OtherAnti-Strip Additives [Kennedy and Ping (1991)] (continued).57

Repititions to Failure300002500020000150001000050000Control Hydrated Lime Liquid Anti StripAdditiveNo Moisture 3% Moisture As Compacted ConditionedFigure 13. The Effect of Additives on Fatigue Life - Oregon Department of Highways FieldStudy [Kim et al. (1995)].Permanent CompressiveMicrostrain807060504030201000 500 1000 1500 2000Number of RepetitionsControl Liquid Anti-Strip Hydrated LimeFigure 14. Effect of Additives (Without Moisture) on Permanent Deformation - OregonDepartment of Highways Field Study [Kim et al. (1995)].58

Pavement CompressiveMicrostrain807060504030201000 500 1000 1500 2000Number of RepetitionsControl Hydrated Lime Liquid Anti-StripFigure 15. Effect of Additives (With Moisture) on Permanent Deformation - OregonDepartment of Highways Field Study [Kim et al. (1995)].250Resilient Modulus 25C, ksi2001501005001 2 3Hydrated Lime, %Trucke (Before) Truckee (After) G. Valley (Before) G. Valley (After)Figure 16.Effect of Hydrated Lime on the Resilient Moduli Before and FollowingLottman Conditioning for Truckee and Grass Valley, California Mixtures[Epps et al.(1992)].59

Resilient Modulus 25C, ksi3503002502001501005000 1 2Hydrated Lime, %Mammouth (Before) Mammouth (After) Moreno (Before) Moreno (After)Figure 17.Effect of Hydrated Lime on the Resilient Moduli Before and FollowingLottman Conditioning for Mammoth and Moreno, California Mixtures[Epps et al.(1992)].Effectiveness Rating876543210Amines (20*) Polymers (7*) Portland Cement (3*) Lime (7*)AdditiveMeanStd. Dev* Note: numbers in parentheses represent number of responses.Figure 18.Relative Effectiveness of Additives in Eliminating or Reducing Moisture Problems[Hicks (1991)].60

Average Diametral TensileStrength, psi1601401201008060402006 12 18 24 30 36 48 60 84 108Evaluation Period, monthsFigure 19.Effect of Time on the Average Diamentral Tensile Strength Based on Corefrom Georgia Field Study [Watson (1992)].61

Severity4.543.532.521.510.50Moderartely SevereModerateSlightVery Slight77L 28L 58L 81L 663C 64NKC 29C 622C 690C 64HC 01CRoutes (L-Lime Additive, C-Chemical Additive)Fine Aggregate Coarse AggregateFigure 20.Severity of Stripping as Determined by Maupin for Virginia Pavements[Maupin (1995)].Percentage of Stripping35302520151050SM-2A (CA) SM-2B (CA) SM-2C (CA) SM-2A (FA) SM-2B (FA) SM-2C (FA)Mix Type (CA-Coarse Aggregate Application, FA- Fine Aggregates Application)ChemicalLimeFigure 21. Average Stripping in Aggregates [Maupin (1997)].62

600500MR (Ksi)40030020010000 2 4 6 8 10 12 14 16 18 20Cycle #Control Lime on Wet Agg. Lime on Wet Agg.Lime on SSD Agg. UP 5000 Liquid Anti-stripFigure 22.Mr Property as a Function of Freeze-Thaw Cycles for the Mixtures onSD 314 [Sebaaly et al. (2003)].600500MR (Ksi) .40030020010000 2 4 6 8 10 12 14 16 18 20Cycle #Control Lime on Wet Agg. Lime on Wet Agg.Lime on SSD Agg. UP 5000 Liquid Anti-stripFigure 23.Mr Property as a Function of Freeze-Thaw Cycles for the Mixtures onUS 14 [Sebaaly et al. (2003)].*Note: two replicate sections were constructed using the lime on wet aggregatetechnique on each project.63

300250Lime MixMr = -0.3571FT 2 + 2.6214FT + 265.25R 2 = 0.9704200Mr (ksi)15010050Liquid MixMr = -0.1323FT 2 - 5.2176FT + 248.86R 2 = 0.918300 3 6 9 12 15 18 21F-T CyclesFigure 24.Relationship between Mr and Freeze-Thaw Cycles for Idaho SH67 Mixtures[Sebaaly et al. (2005)].TSR Value (%)10090807060504030201001.5%BHF, 0%-lime 6.5% BHF, 0%-lime 5.5% BHF, 1%-limePercent BHF and AdditiveBoone BHFEnka BHFFigure 25.TSR Values of the North Caroline Mixtures with Baghouse Fines[Tayebali and Shidhore (2005)].64

3000G*/S in D e lta , Pa (6 4 C )250020001500100050000 10 12 20Percent Hydrated LimeAADAAMFigure 26.Effect of the Addition of Hydrated Lime (percent by weight of binder) onAsphalt Binder Rheology, G*/sin δ [Little (1996)].Percent Permanent Strain1.210.80.60.40.200 500 1000 1500 2000 3600Time of Creep Load, secondsUntreatedLime TreatedFigure 27.Creep Strains Measured After Lottman Conditioning on Natchez, Mississippi,Asphalt Mixture [Little (1994)].65

Permanent Millistrain1201008060402000 5000 10000 15000 20000Loading CyclesControl to aggregate to bitumento bitumento bitumen & AggregateFigure 28.Lime Added to Hot Mix in Various Modes (to the Aggregate or to theBitumen) Strongly Affects the Rut Resistance of the Mixture Even UnderHigh Temperature and Moisture [Lesueur et al. (1998)].Fracture Toughness (kN x m^-3/2)80706050403020100AADType of BitumenAAMUnaged, 0% Unaged, 20% Aged, 0% Aged, 20%Figure 29.Hydrated Lime Improves Low Temperature Toughness of the Lime-ModifiedBitumen [Lesueur and Little (1999)].66

35003000Cycles to Failure250020001500100050002600 2710 835 2752 2861 2958Mixture Stiffness, MPaUntreatedHL- TreatedFigure 30.Hydrated Lime Added to the Bitumen Improves the Toughness of theBitumen and Improves Fatigue Life When Compared tothe Identical Mixture Without Lime [Lesueur and Little (1999)].Log of Aging Index32.521.510.50Boscan Coastal Maya-1 Maya-2Base Asphalt0% 10% 20%Figure 31.Effect of Hydrated Lime in Reducing the Aging Index of Asphalt Binders[Petersen et al. (1987)]67

AAD-1 BinderAging Index60504030201000 100 400 800 2000Aging Time (Hrs)Control 25CControl 60CHL2 25CHL2 60CHL3 25CHL3 60CABD BinderAging Index60504030201000 100 400 800 2000Aging Time (Hrs)Control 25CControl 60CHL2 25CHL2 60CHL3 25CHL3 60CFigure 32.Aging Index of Untreated and Lime-Treated Asphalt Binders[Huang et al. (2002].68

6000Viscosity (60C), Stokes5000400030002000100000 1 2 3 4 5 6 7 8Time in YearsNo AdditiveHydrated LimeFigure 33.Field Data Demonstrating the Effect of Hydrated Lime on the Hardening ofAsphalt Binder Based on Utah Data [Jones (1997)].1210Depth of Rut, mm864200 2 4 6 8 10 12 14 16 18 20Number of Passes, thousandsNo Lime (1) No Lime (2) W/ Lime (1) W/ Lime (2)Figure 34.Results of Rut Tracking Tests from Wuppertal-Dornap, Germany[Radenberg (1998)].69

100908070Percent605040TSRMRR3020100CMS-1 CMS-1(L) CSS-1 CSS-1(L) HFE-150 HFE-150(L)Emulsion (lime)Figure 35.Tensile Strength Ratio (TSR) and Resilient Modulus Ratio (MRR) ofKansas CIR Mixtures [Cross (1999)].60Increase in wet rut depth (%)50403020100CMS-1 CSS-1 HFE-150w/o limew/limeEmulsionFigure 36.Percent Increase in Rut Depth of Kansas CIR Mixtures in the APAUnderwater after 8,000 Cycles [Cross (1999)].70

avg-untreatedlow-untreated54PSI32101 2 3 4 5Yearsavg-treatedlow-treated54PSI32101 2 3 4 5YearsFigure 37. Average and Low Values of PSI for Untreated and Lime-Treated Mixtures on I-80 in Northern Nevada [Sebaaly et al. (2003)].71

Resilient Modulus 25C, ksi8007006005004003002001000Control QL Dry Agg. QL Asphalt QL Slurry HDL Dry Agg. HDL Wet Agg.Method of AdditionBefore LottmanAfter LottmanFigure 38.Effect of the Method of Hydrated Lime Addition on the Retained ResilientModulus After Lottman Conditioning [Waite et al. (1986)].Percent Marshall Stability(80%Minimum)120100806040200No Add. Liquid Add. 1% Lime SSD + 2% 1% Lime + 2% &Mar.Type of TreatmentFigure 39.Effect of the Type of Additive and Method of Addition on the Retained TensileStrength of Materials from SR-50, Millard County Line to Salina, Utah[Betenson (1998)].72

Percent Retained Tensile Strength140120100806040200No Add. 1% HL + 2% SSD 1% HL + 2% Mar.Method of TreatmentFigure 40.Effect of Method of Lime Addition on Tensile Strength Ratio for Materials fromI-70 Wetwater to Colorado Line, Utah DOT [Betenson (1998)].Percent Retained Strength120100806040200No Add. 1% HL Dry No Add. 1% HL Dry 1% Lime + 2% &Mar.Method of TreatmentImmersion CompressionLottman Test* 2% & Mar.: 2% moisture above SSD with marination.Figure 41.Effect of Method of Lime Addition on the Retained Compressive and TensileStrengths for Main Street in Richfield, Utah [Betenson (1998)].73

140120Percent Retained100806040200No Add. 1% HL Dry No Add. 1% HL SSD + 2%Method of TreatmentImmersion CompressionLottman Test* SSD + 2% = saturated surface dry plus 2% additional waterFigure 42.Effect of Method of Lime Addition on Retained Compressive and Tensile Strengthfor I-70 Spring Canyon to Wide Hollow, Utah [Betenson (1998)].140Percent Retained Stability120100806040200Quarry AMix BQuarry AMix HQuarry BMix BQuarry BMix HQuarry GMix HQuarry EMix HQuarry DMix HQuarry EMix BMaterial TypeNo Lime Lime- Filler Lime- SlurryFigure 43.Effect of the Addition of Lime and Method of Addition onthe Retained Stability for Georgia DOT Mixtures [Collins (1988)].74

Percent Retained TensileStrength120100806040200None Pugmill 2-day StockpileMethod of ApplicationNo HL Dry HL Lime SlurryFigure 44.Effect of Method of Application on Retained Tensile Strengths ofBatch Plant Operations in Texas [Button and Epps (1983)].Retained Tensile Strength140120100806040200None Cold Fedd Drum 2-day Stockpile 30-dayStockpileMethod of TreatmentNo HL Dry HL Lime SlurryFigure 45. Effect of Addition of Lime to Drum Plant Operations [Button and Epps (1983)].75

Tensile Strength Ratio (%)120100806040200No additive Lime slurry Dry lime &wet aggDry lime &dry aggDry lime &wet sandMix 1 Mix 2Figure 46. Impact of Lime Addition Method [Tahmoressi and Mikhail (1999)].Percent Retained TensileStrength1.61.41.210.80.60.40.20Cb dry s + 2 Cd CFB CD FS WS PG TA FS WS PG TA TA +30Method of ApplicationBatch PlantDrum PlantCb = No Lime, Dry = Dry Lime in Pugmill, S + 2 = Slurry on Total Aggregate + 2-Days inStockpile, Cd = Control + No Lime, CFB = Dry Lime on Total Aggregate at Cold FeedBelt, CD = Dry Lime at Center Drum Through Fines Feeder, FS = Slurry on Field Sand atCold Feed Belt, WS = Slurry on Washed Sand at Cold Feed Belt, PG = Slurry on PeaGravel at Cold Feed Belt, TA = Slurry on Total Aggregate at Cold Feed Belt,TA + 30 Day = Slurry on Total Aggregate + 30-Days in StockpileFigure 47.Effect of Method of Addition of Lime on Tensile Strength Ratio forBatch and Drum Plants [Button (1984)].76

120Percent Retained Strength100806040200No Lime 0.3% Lime on Sand 1.1% Lime on Sand 1.2% Lime on SandType of TreatmentFigure 48. Effect of Amount of Lime Added to Field Sand [Kennedy et al. (1982)].120Percent Retained TensileStrength10080604020034-35 45-60 60 60-90Time in Stockpile, daysNo LimeLime- TreatedFigure 49.Effect of Time of Stockpile Marination on the Tensile Strength Ratio ofMississippi Siliceous River Gravel Aggregate [Little (1994)].77

160Tensile Strength Ratio1401201008060402000.5 1 1.5Lime Percent by Dry Weight of All AggregateNo Lime Dry HL Dry HL to FA LS LS to FAFigure 50.Effect of Method of Lime Addition and Percent of Lime Addedto Granite Aggregate [Hanson et al. (1993)].78

Percent Hydrated Lime Remaining1201008060402007 14 21 28 35 42 49 56 63 70 77 84 91 98 105 112 119 126 133 140 147 154 161 168 175Exposure Time, days1 in. 2 in. 3 in. 4 in. 5 in.Figure 51. Effect of Exposure Time and Stockpile Carbonation on the Active Ca(OH) 2 Remaining [Graves (1992)].79