Experimental investigation for dynamic characteristics of paraffin-graphite based CPCM (composite phase change material) amended expansive soil under dry-wet cycles

Expansive soils are known to exhibit complex behavior under varying moisture and stress conditions, leading to soil cracking and instability. In this study, the effects of composite phase change material (CPCM) on the dynamic characteristics of expansive soils before and after dry and wet cycles were investigated. Further, the soil with and without CPCM amendment was also subjected to dry-wet cycles so as to monitor cracking phenomenon. Dynamic triaxial tests were conducted to evaluate the damping ratio and elastic modulus of expansive soil amended with CPCM. For interpretation of the cracking and dynamic properties of CPCM amended soil, laser thermal conductivity and electron microscope scanning tests were conducted. The results showed that the incorporation of CPCM material effectively inhibited soil cracking by reducing the temperature gradient difference within the soil and actively regulating the temperature distribution. Moreover, the CPCM amended expansive soil demonstrated better stability under the combined effect of alternating load and wet and dry cycles. The dynamic modulus of elasticity of the 10% CPCM amended soil was found to be about three times that of the bare soil. Additionally, the CPCM material improved the soil structure and reduced the damping ratio and the generation of pore water pressure in the expansive soil. Overall, this study demonstrates the effectiveness of using CPCM materials to improve the dynamic characteristics and stability of expansive soils, making it more suitable as roadbed filler.