Asphalt Review - Volume 32 Number 3 (Jun / Juy 12) - Australian ...

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ASPHALT REVIEWNew PMB Specificationfor AustraliaThe latest edition of the national specification framework for polymermodified binders and multigrade bitumens has now been introducedand is the new reference document describing the grades of PMBsand Multigrade bitumens available for use in asphalt and sprayedseals in Australia.The specification document, known as AGPT/T190 – SpecificationFramework for Polymer Modified Binders and Multigrade Bitumens,has been produced by an Austroads Project Group and succeeds theprevious version of the specification AP-T41 from 2006.The updated specification introduces upper limits to the testproperties of softening point and torsional recovery for PMBs. Thismeans that binders must now be manufactured to meet an allowable“window” for these two properties compared with the previousversion of the specification that only required minimum values. Thesespecification limits have been derived from nationally coordinatedfield trials and laboratory studies as well as statistical analyses ofproduction data.A new sprayed seal grade S15E has also been introduced and theold A30P asphalt grade has been removed from the specification.AGPT/T190 also includes the requirements for Multigrade bitumenand field produced Crumb Rubber binders, although these remainunchanged from the previous edition of the specification. AllAustroads Polymer Modified binders, Multigrade bitumen should nowbe procured in accordance with the new specification.The sister document providing guidance on the selection and useof polymer modified binders and multigrade bitumens (previousedition AP-T42) is currently undergoing a revision and will be availablethrough Austroads later this year.This ready to use pre-mix bituminous mixture is manufactured from selective aggregates,bitumen and a co-polymer creating a tenacious bonding material for permanent use andrepairs. <strong>Asphalt</strong> in a Bag is an all weather road repair solution. It can be applied at -26degrees Celcius and will perform just as well during hot and rainy days at temperaturesreaching 49 degrees Celcius..7949278AA
ADVERTORIALDD25 – all-round specialistfor smaller jobsDesigned for smaller compaction projects,Volvo’s DD25 and DD25W are small doubledrum compactors that feature 360-degreevisibility and high frequency – allowingoperators to complete the job faster, betterand more safely.The DD25 from Volvo ConstructionEquipment offers operators exceptional allroundvisibility, thanks to the seating positionand an unobtrusive engine cover. Whethercompacting forwards or in reverse, the drumedges are clearly visible, allowing precisecompaction and increased safety. The abilityto clearly see the work area reduces neckstrain on the operator and avoids bumps andscrapes on the machine.For a perfect mark-free matThe 2,450 kg (5,400 lb) DD25 is a highfrequency compactor that allows increasedtravel speeds while maintaining thecorrect impact spacing – resulting in a highquality, smooth finished asphalt surface.Depending on application, the frequencycan be adjusted from 3,300 vpm/55 Hz to4,000 vpm/67 Hz. There are a number ofapplications that could require a changein frequency settings to maintain matsmoothness and density, ranging fromsite maneuverability to mix design andasphalt temperature.The frequency is altered by repositioningthe engine throttle lever. Mat smoothness isalso secured by an automatic vibration stopsystem, which eliminates the possibility of theoperator forgetting to turn off the vibrationand damaging the asphalt surface.The drums themselves are worthy ofmention: they’re machined to be perfectlyround, while the outer 20 mm (0.78 in) of thedrum is chamfered and the edges are given arounded 9 mm (0.35 in) radius profile. Thesefeatures contribute to a smooth rolling finishthat doesn’t mark the asphalt, meaning fewerpasses are required for the perfect result. Bothdrums are fitted with wipers made of urethanefor effective cleaning and longer life, even onabrasive surfaces. Urethane has a higher cutand-tearresistance than the more commonlyused rubber.Front and rear drums feature a pressurizedwater system that helps eliminate asphalt pickup and damage to the pavement surface. Therust-proof system provides a constant flow tothe drum surfaces, and fine filters behind eachof the spray nozzles minimize clogging andmaintain proper “fan” spray coverage to thedrum surfaces. The brass nozzles and screensare designed for quick removal – without theuse of tools – if a blockage occurs.Water flow is maintained by a diaphragmpump and primary water filler. The spray isalso adjustable, with the operator selectingthe intervals between water sprays to thedrum. Lengthening the time between sprayactivation (if appropriate) can considerablyreduce unnecessary water use, and reducetime spent refilling the water reservoir. Thewater level can be easily monitored by a gaugemounted on the tank.Another major feature of the DD25compactor is a new fuel efficient threecylinderdiesel engine which produces 24,8kW. A switch located in the seat will shutdown the machine’s engine and apply thebrakes should the operator get off the seat,maintaining safe operating conditions.Easy maintenanceBoth drums feature maintenance-freeeccentric bearings that are sealed andlubricated with lithium grease to toleratehigher temperatures and rotating speeds.All service points are easily accessible, thanksto a lightweight forward-tilting engine hood,which is supported by a pair of gas struts.Daily checks can be reached from groundlevel, helping ensure that maintenance isproperly conducted. A service chart on theengine hood, gives maintenance intervals andlubrication requirements. Servicing is madeeasy by grouped remote hydraulic and engineoil drain hoses housed in a side accessedcompartment.Key features of the Volvo DD25:Operating weight kg (lb) Drum width mm (in) Drum diametermm (in)Vibration frequency Hz(vpm)Vibration centrifugalforce kN (lb)DD25 2,450 (5,400) 1,000 (39.4) 700 (27.6) 55 (3,300) & 67 (4,000) high 37 (8,318) low 25(5,620)DD25W 2 600 (5,730) 1,200 (47.2) 700 (27.6) 55 (3,300) & 67 (4,000) high 40 (8,992) low 28(6,295)ROADS JUNE/JULY 20<strong>12</strong> 49
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Asphalt Review - Volume 32 Number 3 (Jun / Juy 12) - Australian ...

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