Developing New Geomaterials: The Case of the Natural Rubber Latex Polymers in Soil Stabilization

This study explores using natural rubber latex (NRL) as a sustainable polymeric additive to improve the mechanical performance of cement-stabilized soil-crushed limestone waste (CLW) mixtures for pavement base applications. The experimental program involved varying cement contents (3%, 6%, and 9% by weight of soil) and NRL replacement levels (10%, 15%, 20%, and 25% of an 18% optimum water content, as determined by the standard Proctor test) under two target dry unit weights (16.6 and 17.6 kN/m³) and curing periods of 7 and 28 days. Unconfined compressive strength (UCS) tests and stiffness (Go) measurements were performed, while microstructural developments were examined using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results indicate that an optimal NRL replacement exists for each cement content, enhancing interparticle bonding through the formation of polymeric films that reduce porosity and improve the ductility of the matrix. However, excessive NRL was found to retard cement hydration and ultimately decrease strength. On average, a 28-day curing period produced a 38% increase in UCS over 7-day values, independent of the NRL dosage. Comparisons with literature standards, including the ASTM D4609 threshold of 345 kPa for field strength, confirm that the optimized mixtures meet and exceed the minimum performance requirements. These findings underscore the potential of NRL as a viable alternative to conventional synthetic latexes in sustainable pavement base materials.