PHASE II REPORT - Caltrans

This process should be repeated with different filler types (if necessary) to optimize the mixture
for constructability and performance criteria. This will lead to a recommended filler type and
additives levels to be used.
Step 3: Determine the Short-term Constructability Properties
This step consists of taking the acceptable mixes and conducting cohesion testing using the
ACT. The cohesion test is performed at 60 minutes and after 24-hours of cure. This testing
would be repeated for specified application conditions of the project. If the results do not meet
the standards, then the mixes and materials would be modified as required. In all cases, it is
important to ensure that the mix time and spreadability are acceptable. Spreadability is a
measure of the ability of the mix to be placed and finished on the pavement surface.
After the proportions have been selected, the ACT test should be performed and repeated for
anticipated curing conditions to evaluate the short-term abrasion properties.
The mix proportions can then be modified if necessary and a check performed to confirm that
the cohesion at 60 minutes provides an acceptable traffic time and the cohesion at the 24-hour
cure period is also acceptable.
The results of step 3 are used to establish a target optimum for the next step in the design, and
to evaluate the short-term abrasion properties of the selected mix.
Step 4: Determine the Optimum Binder Content
This involves preparing selected samples for the specific application conditions and varying the
emulsion content ±2% from the target optimum. The additive and filler proportions will remain
as determined from the targets developed in step 3.
Under this step the WTAT will be performed at 1-hour and 6-day soak periods followed by tests
using the LWT to determine the excess asphalt at 77°F (25°C).
The recommended optimum binder content will be selected by evaluating the abrasion loss in
the WTAT test and the binder content versus sand adhesion from the Loaded Wheel Tester
(LWT).
NOTE: The specification minimums established by this study will be used for abrasion loss and
the maximum for sand pick up from the LWT.
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