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4.4 REVISED MIX DESIGN METHOD (VERSION 2)<br />
After the evaluation of the proposed mix design method, and due to the available time available<br />
to complete the project, the following revisions were made to the mix design method:<br />
• To determine the optimum binder content (step 4), it was the original intent to run the<br />
LWT at three different temperatures: 95°F (35°C), 77°F (25°C), and 59ºF (15°C). This<br />
will be modified to run the LWT at 77°F (25°C) only.<br />
• To determine deformation properties, the proposed mix design method recommended<br />
using TB-109. The revised method will measure deformation properties using TB-147<br />
instead.<br />
The mix design method reflecting the two revisions discussed above will be as follows:<br />
Step 1: Materials Selection<br />
To begin the mix design, the current ISSA recommendations will be used. Step 1 is subdivided<br />
into the following steps, in the order given:<br />
• Selection of aggregate: The first step is to choose the aggregate grading based on the<br />
existing ISSA specifications. In addition, the selected aggregate must meet the<br />
minimum requirements for mechanical and chemical properties in the specifications<br />
prepared as a result of this study.<br />
• Selection of the emulsion and binder: This will be largely a matter of the climatic<br />
conditions where it will be applied, and available supply. These parameters are included<br />
in the project’s specifications.<br />
• Selection of a locally available potable water source.<br />
• Selection of a mineral filler, Portland cement, or hydrated lime, which meets the<br />
specification requirements.<br />
• Selection of a liquid retardant such as Aluminum Sulfate when necessary.<br />
• Include a set control additive at the addition rate recommended by the emulsion supplier<br />
if necessary.<br />
Step 2: Create a Mix Matrix and Determine Mix Constructability<br />
After the materials have been selected, it will be necessary to determine the proportions of<br />
aggregate, water, emulsion, and additives to create a mix matrix. This step will involve the use<br />
of the AMT test to determine the mix and spread indices. With the results of the AMT, the<br />
conditions at which the materials can be mixed safely and placed in a timely fashion can be<br />
determined. These tests will be performed at standard laboratory conditions and repeated for<br />
selected mixes for a range of anticipated application conditions.<br />
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