Effect of Moisture on Performance of Mixture of Sand-Fouled Ballast and Tire-Derived Aggregates under Cyclic Loading

Abstract

The optimum weight percentage of tire-derived aggregates (TDAs) mixed with ballast, as a new approach to rehabilitate the performance of ballast layer in desert areas, has been suggested as 5% in the presence of sand fouling. The current paper is devoted to the effect of moisture content (MC) on the mechanical behavior of sand-fouled ballast with and without TDAs. A number of ballast box cyclic tests were conducted on mixtures of fully fouled ballast, TDA, and water. The samples contained 0% and 5% of TDAs by ballast weight as well as 0%, 5%, 10%, 15%, and 20% of MC by sand weight. The gradation of ballast and TDAs was in accordance with current standards, and the particle size distribution of sand ranged from 0.075 to 0.84 mm. The parameters measured are the settlement, stiffness, and damping of samples, which did not follow a constant trend by varying the MC. According to the laboratory results, an MC of 5% decreased the settlement and increased the stiffness and damping of fouled non-TDA samples, whereas increasing the MC up to 10%, these samples experienced their minimum stiffness as well as maximum settlement and damping. Inclusion of TDAs had no effects on the variation trend of settlement and stiffness versus the MC. Consequently, from a practical standpoint, the MC of 10%, which eliminated the influence of TDAs on the sample damping, was regarded as the critical moisture content.