Improving clay-geogrid interaction: Enhancing pullout resistance with recycled concrete aggregate encapsulation

In this study, Recycled Concrete Aggregate (RCA) was employed as a sandwich technique around the geogrid to enhance the pullout resistance of the geogrid in clayey backfills. Large-scale pullout tests were conducted on three configurations: geogrid-reinforced clay, geogrid-reinforced RCA, and geogrid sandwiched between layers of RCA, aimed at investigating pullout resistance and deformation. The experiments encompassed two different geogrid types (designated as G1 and G2), varying normal pressures ranging from 10 to 50 kPa, and RCA layers with thicknesses of 40, 80, 160, and 320 mm. Results from the experiments revealed that the inclusion of RCA layers around the geogrid substantially enhanced pullout resistance, with improvements ranging from 1.5 to 3 times compared to clay specimens. Optimal RCA thicknesses were determined in order to enhance soil-geogrid bonding and pullout resistance. For G1 geogrid, a thickness of 160 mm (equivalent to replacing 25% of clay volume with RCA) was identified as optimal, while for G2 geogrid, an 80 mm thickness (equivalent to replacing 15% of clay volume with RCA) was found to be sufficient. These thicknesses were established to achieve over 80% of the pullout force compared to full RCA specimens.