Mechanistic evaluation of biaxial and triaxial geogrids and geocells reinforcing C&D waste aggregate layers for sustainable flexible pavements

Integrating geosynthetics with recycled aggregates in pavement construction presents a technically reliable and environmentally sustainable alternative to natural aggregates, aligning with circular economy principles. This study evaluates the structural performance of geosynthetic reinforced base layers constructed using 100 % recycled aggregate (RA), sourced from a construction and demolition (C&D) waste processing facility, and compares the performance of base layers prepared with natural aggregate (NA). A series of static plate load tests were conducted on reinforced and unreinforced sections over subgrades with CBR values of 3 % and 9 %, incorporating biaxial geogrids, triaxial geogrids, and geocells at varying depths. For the tested configurations, geocell reinforcement with a 150 mm cell depth achieved the highest modulus improvement factor and layer coefficient ratio placed corresponding to optimal placement depth (u/a of 0.33). Similarly, triaxial geogrid (GRD1) exhibited superior performance at a placement depth of (u/a of 0.33) among geogrids, while biaxial geogrid (GRD2) exhibited moderate improvements for both the test conditions (i.e., base layers with recycled and natural aggregates). Furthermore, unreinforced and reinforced pavement layers with recycled aggregates achieved resilient moduli within the range of 261.6 MPa and 746.6 MPa, enabling significant impact on the pavement layers while maintaining critical strains within permissible limits. The findings provide novel insights into the comparative structural behaviour of pavement layers constructed using recycled and natural aggregate consisting of wet mix macadam (WMM). Additionally, the quantified improvement factors can conform to mechanistic empirical pavement design frameworks, supporting the development of sustainable and structurally efficient pavement systems.