Heavy-Duty Flexible Bases: Year 3 Progress Report

In Year 3 the laboratory test protocols for measuring the resilient modulus and permanent deformation properties of granular bases were further developed. A repeatability study was conducted, and studies were also made on the influence of sample size. A comparison was made with samples molded to the recommended dimensions (6 inches by 12 inches (high) to the standard Texas Department of Transportation (TxDOT) size, 6 by 8 inch. Using a high-quality base material from Spicewood Springs, it was found statistically that the resilient modulus values were not affected by using a smaller sample size. Experimental test sections were also constructed with three premium bases that meet the proposed Item 245 specification. Preliminary laboratory test results are presented on these bases together with details of the test section construction. The Tube Suction Test continues to be a good test to identify good base materials; it clearly distinguished between the Item 245 and Item 247 materials. No clear distinction could be made with other tests such as resilient modulus. Numerous problems were encountered with running the low-fines bases through the traditional strength testing. We found problems with both the compaction and testing. A new vibratory compaction system was built, and it will be evaluated in Year 4 of this project.