Abstract
A study was conducted to stabilize An Nafud desert sand against wind-induced erosion employing enzyme-induced carbonate precipitation (EICP) assisted by a sodium alginate (SA) biopolymer. Biopolymers occur naturally in brown seaweed, are inexpensive, and are used extensively in the food, textile, and paper industries as thickeners and emulsifiers. A wind tunnel experiment was conducted to evaluate the wind erosion rate of samples treated surficially by spraying various concentrations of mixes using EICP and SA solutions. The unconfined strength of the resulting crust that formed was measured with a hand penetrometer. Scanning electron microscope (SEM) imaging and X-Ray diffraction (XRD) were conducted to study the microstructure and to identify the presence of crystalline materials, respectively, in treated and untreated sand samples. The results indicate that combining EICP and SA led to a significant improvement in the erosion rate by 100% compared to the untreated samples, with effective results recorded at lower concentrations of SA. The improvement is mainly attributed to the inter-particle bonding effect of both the carbonate precipitant and the biopolymer. The unconfined strength of the crust that formed by means of the solution treatment increased with an increase in the concentration of the biopolymer. This increase is attributed to the lower viscosity of the biopolymer solution and the cross linking of the biopolymer due to the presence of divalent calcium ions. The soil treated with EICP alone had the lowest strength, and increments in the molar concentration of the calcium chloride had no effect on the surface strength.