Experimental Evaluation of Nano-material and Biopolymer Additives on Expansive Subgrade Soil for Pavement Applications

This paper presents the experimental observation of nano-material and biopolymer additives on expansive pavement subgrade. Nanomaterials, including nano-lime and nano-silica, as well as biopolymer chitosan from shrimp shells, are used. The experimental methods to inspect the characteristics of improved soils are implemented. California Bearing Ratio (CBR) and swelling test are conducted to investigate the strength characteristics of the improved soil. The observations through several tests such as potential hydrogen (pH), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), and cation exchange capacity (CEC) were conducted to visualise the soil microstructure improvement under additive mixtures. The results showed that adding nano-materials with biopolymers led to a significant increase in soil CBR values and a decrease in swelling values. Additionally, microstructure testing confirmed the formation of nano-materials with biopolymers, validating the improvement in soil strength. The pH is also essential to ensure that the chemical improves soil characteristics.