Stress–Dilatancy and Critical-State Behavior of Geogrid-Reinforced Recycled Waste Materials

Waste disposal has become a major challenge due to the increasing production driven by urbanization. Two such wastes generated in substantial quantities are steel slag and construction and demolition waste (CDW). The current study explored the stress–dilatancy and critical-state behaviors of geogrid-reinforced recycled steel slag and CDW for evaluating its suitability in various geotechnical applications. A set of consolidated drained triaxial tests were carried out on test samples, with and without geogrid reinforcement, to achieve this objective. The performance of the steel slag and CDW material was compared with that of commonly used geomaterial, namely, sand. Steel slag exhibited higher strength compared to sand and CDW. At a confining stress of 50 kPa, the strength of steel slag was 1.6 times greater than that of sand, while the strength of CDW was 1.3 times higher than that of sand. The effect of geogrid reinforcement on stress–dilatancy and critical-state behavior was quantified for all the materials. Results revealed that the critical-state line rotates in a clockwise direction in the presence of the geogrid. On the other hand, the stress–dilatancy curve of the materials shifted upward with the inclusion of the geogrid. At a confining pressure of 50 kPa, the peak dilation angles of reinforced sand, slag, and CDW were 0.8, 0.7, and 0.9 times that of the unreinforced specimens, respectively. In addition, the strength properties, energy absorption capacity, and modulus degradation of the materials were also evaluated. A mathematical expression was proposed to relate the energy absorption capacity of the geogrid-reinforced materials with the critical-state stress ratio. Moreover, the Li and Dafalias stress–dilatancy model parameters were proposed to capture the stress–dilatancy behavior of the materials. Overall, encouraging performance of the waste materials was observed for potential geotechnical applications.