The study begins with a general review of the field trial results reported by engineers from seven city districts in Texas, after which the authors summarize their findings. “Limestone Rock Asphalt [LRA] materials,” the researchers went on to write, “continued to give overall good performance and were popular in most all of the districts.” Adding that, in contrast to the other cold mix patches tested, our Limestone Rock Asphalt’s [LRA] “workability and performance under dry conditions was considered exceptional.” In wet and cold conditions, however, the researchers found that “performance of UPM, Instant Road Repair, and LRA was characteristically similar” but that “districts that used all three of these materials in their field tests tended to consider the cost of UPM and Instant Road Repair to be too high.”

“The unique characteristics of LRA,” the researchers exposited, “are derived from its existence in an almost ready-to-use condition in naturally created deposits located almost exclusively in Texas.” This was made evident in the second part of the study, when the researchers put the three asphalt formulations through a battery of laboratory tests to assess their different material compositions.

The researchers suggested that the consistent performance of LRA across dry-wet and hot-cold weather conditions could in part be explained by its native properties. Not only did they note that a high-purity bitumen binder is integrally bound into the LRA aggregate, they also observed that: (hereafter are direct quotes)

1. “LRA commonly exhibits 4-cycle Magnesium Sulfate test loss values of between ~5 and 15 percent. These excellent soundness numbers are attributable to the size, type, and cementation of the fossil shell particles in the lean rock asphalt. The lean rock asphalt is composed of very small fossil shells which are cemented together by coarsely crystalline calcium carbonate. This type of cementation is relatively non-porous, which leaves the magnesium sulfate solution very little opportunity for disruptive duty.”
2. “Excellent polish numbers (38 to 41) are related to the hard fossiliferous-broken shell composition of the limestone. Coarsely crystalline calcite cement crystals, and shell fragments act to generate excellent friction on pavement surfaces.”