Shrinkage Characteristics of Biopolymer Treated Expansive Soil: Fid-Bau Portal

Shrinkage Characteristics of Biopolymer Treated Expansive Soil

Vydehi, K. Venkata / Moghal, Arif Ali Baig / Mariyam Rasheed, Romana

Structures built over expansive soils undergo severe volume change due to seasonal moisture fluctuations. Increased suction with loss of moisture leads to desiccation cracking and soil curling (upward and downward curling) which is a common phenomenon during the soil drying process. To address the detrimental effects of shrinkage, conventional materials such as lime, cement, and fly ash are used as soil stabilizers. In contrast to this, recent studies on soil improvement paying attention to bio-inspired materials due to reduced negative impact on the environment. Among them, biopolymers are recognized as an effective stabilizer to improve soil properties. However, the shrinkage behavior of biopolymer treated soil is not fully understood under different testing conditions. Investigation of surface characteristics (i.e., curling and cracking) is important to assess the effectiveness of biopolymer in soil stabilization. In view of this, the present paper aims to evaluate the shrinkage characteristics of xanthan gum (XG)/guar gum (GG) treated expansive soil at various dosages subjected to uncontrolled boundary conditions. Bar linear shrinkage tests were performed at biopolymer (XG/GG) dosages of 0.5%, 1.0%, 2.0%, and 4.0% by weight of dry soil mass. Results indicate that untreated samples exhibited shrinkage cracks (without curling) with 18.25 mm deformation and 12.9% linear shrinkage value. Xanthan gum treated soil exhibited soil curling behavior (Convex upward) with lift-off height 12.5 mm and 23.5 mm at 0.5% and 4.0% dosage, respectively; whereas guar gum treated soil exhibited surface cracking phenomenon at 0.5% dosage with deformation value of 21 mm and linear shrinkage value of 15.2%; non-uniform division of polygons and minor convex-up curling is observed at 1%, 2%, and 4% dosage. The factors which affect the moisture evaporation, cracking phenomenon, curling state, particle rearrangement, and lift-off height are identified and possible mechanisms are discussed. The current study creates a basis for in depth investigation on shrinkage characteristics of biopolymer treated soil when it is proposed as a subgrade material for pavement application, in erosion control works (slopes), and as landfill cover material.