Cross-linking of biopolymers for stabilizing earthen construction materials

Biopolymers are promising potential soil stabilizers due to their ease of application and stabilization efficacy. Biopolymers are biologically occurring polymers that form hydrogels when added to soil in the presence of water. Hydrogels are three-dimensional polymer networks formed through the interaction of polymer chains with soil particles and pore water. The chemical properties of the biopolymer and external factors (like temperature) affect the physical characteristics of the hydrogels formed. Cross-linking of biopolymer chains with another monomer or biopolymer enables the development of hydrogels with enhanced physical integrity and mechanical properties. Recent studies have shown that the biopolymers, guar and xanthan gums, improve the mechanical and durability properties of soil. As a galactomannan, guar gum naturally forms cross links with xanthan gum, and the study presented here evaluates the impact of this cross-linking on plasticity, shrinkage, strength and durability. Cross-linked specimens with higher guar gum have higher plasticity indices and linear shrinkage; however, when the amount of xanthan gum is increased, these values reduce. Strength tests suggest that cross-linking addresses some of the shortcomings of each biopolymer and improves the overall mechanical behaviour of the soil. The durability performance of cross-linked specimens was found to be comparable with specimens stabilized with individual biopolymers.