The Optimisation Analysis of Sand-Clay Mixtures Stabilised with Xanthan Gum Biopolymers

Abstract

Sand–clay mixtures can be encountered in both natural soils (e.g., residual soils, clay deposits and clinosols) and artificial fills. The method of utilising biopolymers in ground improvement for sand–clay mixtures has emerged recently. However, a full understanding of the strengthening effect of biopolymer-treated sand–clay mixtures has not yet been achieved due to a limited number of relevant studies. In this study, xanthan gum (XG), as one of the eco-friendly biopolymers, was used to treat reconstituted sand–clay mixtures that had various compositions in related to clay (or sand) content and clay type (kaolin and bentonite). A series of laboratory unconfined compression strength (UCS) tests were conducted to probe the performances of XG-treated sand–clay mixtures from two aspects, i.e., optimum treatment conditions (e.g., XG content and initial moisture content) to achieve the maximum strengthening effect and strengthening efficiency for the sand–clay mixtures with different compositions. The experimental results indicated that the optimum initial moisture content decreased as the sand content increased. The optimum XG content, which also decreased with the increasing sand content, remained approximately 3.75% for all sand–kaolin mixtures and 5.75% for all sand–bentonite mixtures if calculated based on clay fraction. While untreated sand–kaolin mixtures and sand–bentonite mixtures had comparable UCS values, XG-treated sand–kaolin mixtures seemed to have better improved mechanical strength due to higher ionic (or hydrogen) bonds with XG and low-swelling properties compared with bentonite. The deformation modulus of XG-treated sand–clay mixtures were positively related with UCS. The variation in UCS and stiffness for each treatment condition increased as the sand content was elevated for both sand-kaolin and sand-bentonite mixtures. An increment in the proportion of the heterogeneous composite formed by irregular sand particles conglomerated with the XG–clay matrix in total soil might be responsible for this phenomenon.

Mechanical and biodeterioration behaviours of a clayey soil strengthened with combined carrageenan and casein

“…The soils treated with carrageenan-casein mixtures presented the highest UCS of 3.21 MPa at m car /m cas = 1:3 due to the synergetic interaction between carrageenan and casein. Several researchers have conducted in-depth analyses of the strengthening mechanism of biopolymer-treated soils [17,21,47,62,77]. In soil containing both fine and coarse particles, the biopolymer molecules may first interact with the clay particles, forming a clay-biopolymer matrix [17,62].…”

“…Several researchers have conducted in-depth analyses of the strengthening mechanism of biopolymer-treated soils [17,21,47,62,77]. In soil containing both fine and coarse particles, the biopolymer molecules may first interact with the clay particles, forming a clay-biopolymer matrix [17,62]. Hence, the silt and sand particles present in the soil could be connected by either biopolymer or claybiopolymer matrix, as shown in Fig.…”

“…It was reported that there exists an optimum biopolymer content affected by both soil composition (e.g. particle size distribution) and biopolymer types [17,62]. Excessive dosage of biopolymers has an adverse effect on soil reinforcement.…”

“…Regarding the biopolymer content, there exists an optimum biopolymer dosage, which is related to the percentage of clay particles in soils [17,62]. Excessive blending content might induce ionic repulsion and/or hydrologic swelling, leading to a reduced soil strength.…”

Biopolymers as Green Binders for Soil Improvement in Geotechnical Applications: A Review

“…Protein based biopolymers (casein and sodium caseinate) continuously enhanced the sand compressive strength significantly up to 5% biopolymer content. Casein-treated sand indicated a higher growth rate in compressive strength in comparison to agar and gellan-treated sands [66,82,[149][150][151]186].…”