Stiffness and Flexural Strength of Cement-Stabilized Recycled Aggregate Mixtures for Pavement Subbase

This study aims to evaluate the suitability of cement-stabilized mixtures of recycled glass (RG), tire (RT), plastic (RP), and crushed recycled concrete aggregate (RCA), in pavement subbase applications. These blends were previously investigated and proved suitable as alternatives to crushed rock for backfilling deep excavated trenches in trafficable areas. This study explores their suitability under stress levels of pavement structural layers, which is important from a practical and material supply point of view. Specialized pavement and geotechnical testing was carried out on three proposed blends stabilized with 3% cement. The resilient modulus (Mr) characteristics were evaluated through the repeated load triaxial (RLT) test. To assess the material strength, the unconfined compressive strength (UCS) test was performed while the flexural strength and fatigue life of the blends were assessed using four-point flexural beam tests. The Mr, flexural stiffness, and fatigue life results were compared with the minimum requirements as recommended by the specifications for road subbase layers. The essential factors influencing the strength and resilient properties of the blends were the contents of RCA and RT. The Mr values for all proposed blends exceeded the minimum threshold required for a subbase layer. However, based on minimum flexural modulus required for subbase layer, one of the mixtures was recommended to be used as a potential alternative to the virgin quarry material.