Updating Bituminous Stabilized Materials Guidelines Mix Design Report Phase II

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.
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