Updating Bituminous Stabilized Materials Guidelines Mix Design Report Phase II

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2. METHODOLOGY 2.1. MMLS3 Test Configuration Some tests initially conducted with the MMLS3 for the investigation of bituminous stabilised materials BSM’s with water exposure. This research included trafficking of nine (9) BSM-foam and BSM-emulsion specimens placed side by side in the water bath, under saturated conditions i.e. with the specimens immersed in water. The research showed that one of the major challenges with wet trafficking of BSM’s is the premature failure of the mixes after water exposure i.e. the test can require termination at less than 5000 wheel repetitions due to disintegration of the specimens, compared with similar tests on HMA that endure for 10 to 20 times longer. It is a challenge therefore to develop a test protocol that provides sufficient testing time i.e. 50 000 to 100 000 wheel repetitions, to develop a sensitivity to the mix’s performance. The solutions to this challenge presented in this study as follows: Modification of MMLS3 Set-up Figure J.6 below present a schematic illustration of the MMLS3 set-up. Figure J.6: Schematic illustration of the MMLS3 The MMLS3 device can apply 7200 wheel loads per hour and needs a single phase 200-240 Volt AC supply at about 1.5kW. The tyre pressure of MMLS3 can be set up to 800 kPa, during the initial tests the tyre pressure set at 650 kPa, which later adjusted to 420 kPa. This pressure is equivalent to a light truck. The reason for a reduction in tyre pressure is to minimize damage on BSMs and extend the test duration. The use of 420kPa also makes it possible to correlate MMLS3 test results with MIST device test results. An air compressor used to calibrates the tyre pressure. The wheel that used in this study is diamond tread tyres. 6
An electric calibration unit used to set the axle wheel load, as shown in Figure J.7. The load of the wheel in initial study set at 1.2 kN, that changed to 1.8kN for correlation with MIST device test set-up. The selected 1.8kN is equivalent to a small truck, and by tensioning the springs, the load of the wheel calibrated to the correct wheel load. CALIBRATION UNIT JUNCTION BOX ELECTRONIC DISPLAY CUT-OUT MACHINE CROSS MEMBER FLANGE A SPRING SUPPORT SPACER NUT A FLANGE B NUT B NUT C PIN WITH CIRCLIP 10 GUIDE WHEEL 10mm GAP RUBBER STOPPER OUTLINE OF TYRE Fig.3: Measuring and setting the wheel lo Figure J.7: The calibration of the wheel load The suspension system of the wheel designed so that the vertical displacement of the wheel, within a range of less than 25mm, does not influence the pressure the wheel exerts on the specimen. The briquettes are placed in a steel beam, Figure J.15, with moulds tightened from the sides of the beam to keep the specimens restrained in one position during testing. The testing set-up however required modification. In the field, the vehicles do not drive directly on the BSM layer i.e. there is always a surfacing above it, so some protection of the surface of the BSM briquettes from ravelling is needed. In reality, the BSM layer is used in the base or subbase, so some load distribution occurs in the overlying layers, as illustrated in Figure J.8. Due to the reduction in the tyre pressures of the MMLS3 for this testing, it would be preferable if the laboratory set-up of the MMLS3 did not include a load spreading layer over the BSM because this would reduce the pore pressure induction during wheel passages. Therefore, the protection or cover should not distribute the stress over the briquettes, as shown in Figure J.9. 7
Page 1 and 2: APPENDIX J Technical Memorandum Upd
Page 3 and 4: findings of the moisture damage tha
Page 5: Figure J.4: The measuring wheel of
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

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