Abdullah Almajed

Traditional soil stabilization techniques, such as cement and lime, are known for their menacing effect on the environment through heavy carbon emissions. Sustainable soil stabilization methods are grabbing attention, and the utilization of biopolymers is surely one among them. Recent studies proved the efficiency of biopolymers in enhancing the geotechnical properties to meet the requirements of the construction industry. The suitability of biopolymer application in different soils is still unexplored, and the carbon footprint analysis (CFA) of biopolymers is crucial in promoting the biopolymers as a promising sustainable soil stabilization method. This study attempts to investigate the out-turn of cross-linked biopolymer on soils exhibiting different plasticity characteristics (Medium & High compressibility) and to determine the Embodied carbon factor (ECF) for the selected biopolymers. Guar (G) and Xanthan (X) biopolymers were cross-linked at different proportions to enhance the geotechnical properties of soils. Atterberg’s limits, Compaction characteristics, and Unconfined Compressive Strength were chosen as performance indicators, and their values were analyzed at different combinations of biopolymers before and after cross-linking. The test results have shown that Atterberg’s limits of the soils increased with the addition of biopolymers, and it is attributed to the formation of hydrogels in the soil matrix. Compaction test results reveal that the Optimum Moisture Content (OMC) of biopolymer-modified soil increased, and Maximum Dry Density (MDD) reduced due to the resistance offered by hydrogel against compaction effort. Soils amended with biopolymers and cured for 14, 28, and 60 days have shown an appreciable improvement in Unconfined Compressive Strength (UCS) results. Microlevel analysis was carried out using SEM (Scanning Electron Microscopy) and FTIR (Fourier-transform infrared spectroscopy) to formulate the mechanism responsible for the alteration in targeted performance indicators due to the cross-linking of biopolymers in the soil. The embodied energy in the production of both Guar and Xanthan biopolymers was calculated, and the obtained ECF values were 0.087 and 1.67, respectively.

In this study, the chemical stabilization of moderately to highly plastic expansive soil using calcium chloride with added cement is introduced as an effective alternative to the conventional approaches using a single additive such as lime, cement, or a by-product of industrial processes. Using only calcium chloride may lead to its leaching or dissolution over time, leaving a collapsing skeleton with weak bonds. The chemical effect produced by additives is dependent on the constituents of the stabilized soil and the curing period considered. Herein, calcium chloride concentrations of 2%, 4%, and 8% with the addition of 2% cement by dry weight of the soil were considered. The main objective of this study is to investigate the addition of a low amount of cement as a binder to improve the strength and durability of a chemically treated expansive soil. The engineering properties were investigated at 3 curing times: 3 days, 7 days, and 28 days. A laboratory investigation was carried out to investigate the effect of the addition of calcium chloride with cement on the swell potential, swell pressure, compression index, suction, and unconfined compressive strength. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) testing was conducted. The X-ray diffraction patterns were recorded to observe the mineralogy of the material. The results confirmed that calcium chloride with cement is very effective for stabilizing the expansive soil. A reduction in the swell potential by 8% and 25% and a reduction in swelling pressure by 28% and 37.4% were observed for 4% and 8% calcium chloride with cement addition. The compression index decreased with the increase in the calcium chloride content.