Evaluation of Stabilized Base Durability Using a Modified South African Wheel Tracking Device (7-2919-1)

This study was initiated to investigate the durability of the cement treated base (CTB) material used extensively by the Houston District. A literature review concluded that the most realistic durability test is the Rolling Wheel Tracker developed by the South Africans. Typical Houston CTBs were tested with this wheel tracker, and the testing procedure was modified so that both linear shrinkage and unconfined compressive strength could also be measured on the same test specimen.|Testing included field samples from SH 36 near Rosenburg, Texas, which had exhibited extensive deterioration after only a few years in service. Tests were also performed at 3 stabilizer contents, on laboratory molded samples of two aggregates. The first was a high quality limestone material with very low PI < 2. The second was a poor material with clay contaminated fines PI = 7.4 (still within TxDOT specifications).|Three conclusions were drawn from this study. First, lack of Abrasion Resistance was not the principal cause of the failure of SH 36 (See Companion Report 2919-2 on Chemical Deterioration). Second, with good aggregates the lower stabilizer content (4%) produced a material which was capable of meeting TxDOT strength requirements and also had acceptable shrinkage and durability characteristics. Third, the CTB containing high PI fines exhibited high shrinkage and it is anticipated that this material would crack extensively in the field.|The modified South African Wheel Tracking Device shows good potential for determining performance related material characteristics which can be used to establish the optimum stabilizer content for any possible base material.