Enhancing strength parameters of Firouzkooh sandy soil improved with Persian herbal gum

Various improvement methods have been proposed to improve the mechanical and physical characteristics of soil for the construction and the other similar matters. One of the improvement methods is using of the environmentally-friendly elements such as Persian herbal gum as a renewable hydrocolloid biopolymer. Regarding this, in the present laboratory study, the effect of adding this gum to the Firouzkooh sand (No 161) was investigated. Persian gum-water mixture was added in different percentages relative to the weight of dry soil, and the created samples were subjected to unconfined compressive strength test to identify the optimal conditions of the composition. In spite of the variability of the weight percentages of water and gum added to the soil, the effect of the weight of the soil, curing temperature (room or oven temperature), and curing time (7 to 56 days) were investigated. To interpret the effect of Persian gum addition, several scanning electron microscope tests were performed on selected dry samples. The results clearly revealed an increase in the unconfined compressive strength of the samples improved with Persian gum up to 4 MPa due to the presence of many carboxyl and hydroxyl groups in the gum. Samples cured at room temperature with relative humidity of 15% displayed lower unconfined compressive strength than similar samples cured in an oven temperature due to the hydrophilic properties of herbal gum and increased flexibility of the created bonds.