The Role of Biopolymers on the Water Retention Capacity of Stabilized Sand

The application of biopolymers for sand stabilization has recently gained attention due to their natural composition, which makes them both environmentally friendly and of reasonable cost. Measuring the soil–water retention curve (SWRC) of biopolymers-treated sand is essential for the design, modeling, and interpretation of the unsaturated behavior of these materials. Unsaturated shear strength, unsaturated flow, and associated retention capacity are well addressed and evaluated using SWRC. Therefore, this study examined the possible effects of biopolymers—sodium alginate (SA), guar gum (GG), and pectin (P) on the SWRC and retention capacity for stabilized sand. Apart from natural sand, three different concentrations were investigated for each biopolymer. The SWRCs were measured over the entire practical range of suction using a combination of three techniques: hanging column for low suction measurement, axis translation techniques for moderate suction measurement, and vapor equilibrium technique for high suction measurement. The results indicate significant changes in SWRC, and a new series of micropores was developed, this, in turn, extends the desaturation zone of treated sand from a low suction range (i.e., 30 kPa) to moderate to high suction levels (i.e., 10,000 kPa). The saturated water content ( w s ) was slightly reduced, air entry values (AEVs), and residual suction ( s r ) significantly increased and multiplied up to 200 and 75 times respectively. The retention capacity increased, exhibiting a dependency between the biopolymer type and suction range. The results are of great significance for both practitioner engineers and researchers in predicting the unsaturated soil functions of treated sand.