Biopolymer stabilization of highly plastic silty soil for rammed earth construction materials

Abstract

Earthen construction materials (ECM) have been used in India since ancient times in the form of rammed earth blocks and mud house walls. The subsoil is often stabilized with lime/cement to improve its performance and durability. The use of lime/cement promotes the carbon footprint due to their high embodied energy. On the other hand, soil stabilization with biopolymers such as Xanthan Gum (XG) has demonstrated promising results in strength enhancement and negligible ecological risks. The ECM is expected to have a high Unconfined Compressive Strength (UCS) along with low erodibility and thermal conductivity. The current study investigates the influence of biopolymer amendment vary-ing from 0.5% to 1.5% by weight of soil on the UCS, erodibility, and thermal characteristics of an abundantly available highly plastic silty soil in the Brahmaputra valley of the Assam region of India. The study reveals that the increment in biopolymer content results in a four-fold increment in the UCS of bare soil with no practical variation in the thermal conductivity, implying their potential to provide thermal comfort as a building unit. However, the pocket erosion test revealed that although the biopolymer treatment drastically enhances the erosion resistance of untreated soil, the proposed ECM remains in medium erodibility class, limiting its applicability in infrastructures designed for the long term. Nonetheless, the proposed ECM can be utilized effectively as a building unit for the rapid construction of temporary infrastructure, specifically for armed forces and highway engineers that are required to stay at a workstation transiently.