Updating Bituminous Stabilized Materials Guidelines Mix Design Report Phase II

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1. BACKGROUND AND INTRODUCTION 1.1. Terms of Reference Moisture ingress has a detrimental influence on BSMs, both in terms of stiffness and strength of the material. In order to develop more reliable laboratory testing techniques, a more robust link between laboratory properties of the material and field performance needs to be established. Accelerated Pavement Testing (APT) with devices such as the MMLS3 can serve to provide that link. The advantages of APT testing include the evaluation of a range of variables in a relatively short period of time. This is particularly applicable to BSMs because ranges of different types of binders used in practice, namely: • Emulsion • Emulsion and Cement • Foam Bitumen • Foam Bitumen and Cement Each of these binders, along with the aggregates, reacts differently to exposure to moisture. The knowledge and understanding of the mechanisms of moisture damage and the main factors influencing the deterioration need further extension. In addition, reliable limits need establishment for tests on materials exposed to moisture. Variables such as binder types, aggregate types, active fillers, compaction, curing, manner and harshness of moisture exposure, as well as the impact on material properties, requires investigation. 1.2. Task Objectives In terms of the findings of the Inception Study report, the objectives of Task 10 were to: • Investigate accelerated pavement testing procedures using an MMLS3 on various <strong>Bituminous</strong> Stabilised <strong>Materials</strong> (BSMs) including moisture exposure, • Investigate the performance of the BSMs above with water exposure, using wheel tracking tests, and • Validate the behaviour of the selected durability/moisture sensitivity test method outlined above with the results of the accelerated tests. • Make appropriate recommendations regarding the use of the APT device on the screening BSMs based on the moisture related damage. Task 9 has outlined the development of the Moisture Induced Sensitivity Test (MIST) apparatus that developed for the conditioning of triaxial specimens for the evaluation of the resistance to moisture of these materials. The objective of Task 10, in short, is therefore to validate the 2
findings of the moisture damage that observed through MIST conditioning. The setting for loading pulse duration and pressure of the MIST apparatus was influenced by the load duration and stresses of the wheel loads applied to the materials by the MMLS3 APT device. Therefore, a rational analysis should be possible. 1.3 MMLS3 Accelerated Pavement Testing device The scaled testing of pavement structures and surfacing is becoming a standard in the industry. This is due to the advantages associated with evaluating and grading of the asphalt mixes proceeding to construction, (Walubita et al., 2002). The development of the Model Mobile Load Simulator Mk3 (MMLS3) contributes significantly to Accelerated Pavement Testing (APT) method. The performance prediction of a pavement tested for rutting, fatigue, and susceptibility to moisture damage is possible. All of these failure mechanisms can be evaluated in the field i.e. under full-scaled conditions or in a laboratory under controlled conditions. In the laboratory, all the variables that have an influence on the properties of the pavement materials can be controlled during MMLS3 testing. The need for the development of standardised test protocols for testing BSMs with the MMLS3 arises to make certain that the result that produced is reasonable and comparable. A standardised testing platform ensures uniformity in results and increases the confidence in the results. The MMLS3 consists of four axles and each axle has a 300mm diameter inflatable pneumatic wheel on it that circulates in a vertical closed loop. The wheels are supported in bogies that linked by a continuous chain. The wheels are powered by an electric motor that drives a drum, which draws the wheels over the testing bed. The MMLS3 can also apply lateral displacement (wander) of plus or minus 80mm around the central axis. The four wheels are loaded by means of a swing-arm and a spring. The four wheels exert the load on specimens underneath the MMLS3. The speed of the wheels controlled at maximum of 2.5m/s, which is equal to 7200 wheel loads per hour. The testing conditions are controlled, and it is possibility to do tests at temperatures within a range of 0ºC to 60ºC. Figure J.1 provides an illustration of the MMLS3 test set-up. Figure J.1: MMLS3 in testing mode 3
Page 1: APPENDIX J Technical Memorandum Upd
Page 5 and 6: Figure J.4: The measuring wheel of
Page 7 and 8: An electric calibration unit used t
Page 9 and 10: 2.2 BSMs for MMLS3 testing The inte
Page 11 and 12: Figure J.12: The side view of the b
Page 13 and 14: The set-up of the test before traff
Page 15 and 16: 3. TEST RESULTS The use of vinite o
Page 17 and 18: Table J.7: ITS results after wet an
Page 19 and 20: Table 11: Ravelling-depth after MML
Page 21 and 22: Table 15: Tensile Strength Retained
Page 23 and 24: The comparison of BSMs on Figure J.
Page 25 and 26: From Figure J.19 it can be seen tha
Page 27 and 28: 4.3 Saturation Level The moisture i
Page 29 and 30: Ravelling-Depth [mm 16 14 12 10 8 6
Page 31 and 32: From the study conducted in MIST de
Page 33 and 34: - No sign of significant initial de
Page 35: 5. BIBLIOGRAPHY ASPHALT ACADEMY. 20

Updating Bituminous Stabilized Materials Guidelines Mix Design Report Phase II

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