Quality Control & Mix Design Operations

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n 2018, Ajax made an investment to incorporate advanced performance tests to its Quality Control (QC) and Mix

Design Operations. Ajax became one of the few contractors to have these in-house testing capabilities. Performance tests were used in 2018 on new mix designs to ensure that the produced mixes would have the best possible quality in the field. The tests were also used for forensic evaluations of existing pavements. Asphalt mix design has been conventionally based on what are called “volumetrics” of the mix (air voids, VMA, VFA, etc.). The industry has recognized that volumetrics are properties that might not always account for the great number of variables that affect asphalt mixes while they are in service. For this reason, a new generation of asphalt tests were developed. These technologies are meant to test the performance and response of asphalt mixes to conditions that accurately resemble the multiple

The Ajax distresses and factors that are found on the roads Leadership Team while the mixes are in service. wanted to jump The most popular of these performance tests have ahead the fo and be refront at of been used to improve mix designs for rutting and cracking resistance, which are the most common modes of failure in asphalt pavements. Due to the innovation. complexity and the cost of the required equipment, full adoption and widespread use of these advanced performance tests in mix design are still expected to take several years. The Ajax Leadership Team looked at this and wanted to jump ahead and be at the forefront of innovation. With the investment made by Ajax, its QC Mix Design Lab is currently equipped with performance testing equipment that will help improve the mixes with resistance to rutting, moisture damage, cracking initiation and propagation, and bond strength. The performance testing equipment is described below.

Asphalt Pavement Analyzer (APA) Wheel Tracker:

By Alfredo Castro QC Engineer

This device measures the rutting resistance of mixes by applying actual wheel load cycles to compacted asphalt samples or field cores in a closed chamber at a controlled temperature. Wheels go back and forth on top of an asphalt sample to simulate the traffic loads the mix experiences in the field. The temperature can be adjusted to the conditions that the pavement is expected to endure while it is on service. The tests can also be run with the chamber flooded to determine the resistance of the mix to moisture damage and stripping.

SCB Device:

An Auto SCB was also acquired. This device is used for conducting mechanical testing of asphalt. This system is able to perform a wide range of advanced tests that determine the resistance of an asphalt mix to crack initiation and propagation, like the IFIT, IDEAL, and several other monotonic cracking tests. These tests are performed on trimmed semicircular asphalt samples obtained from larger Superpave pills. Another use for this device is for testing the bond strength of different layers of asphalt through the Shear Bond Strength test.