Gypseous soils are problematic soils that cause large deformations in the constructions that are built on it. Therefore, many binders have been used to reduce this impact. Traditional soil binders like lime or cement have environmental problems in terms of sustainability. Thus, sustainable substances have attracted appreciable interest in recently soil enhancement. Biomaterials are being developed to enhance geotechnical engineering properties like hydraulic conductivity, strength, and slope stability of varied soil types. This study aims at evaluating the engineering characteristics of gypseous soil treated with xanthan gum biopolymer. The tests performed on three types of gypseous soil with various gypsum contents and different properties. Gypseous soils were mixed with various contents of xanthan gum with a percentage of 2, 4, and 6. The compaction results indicated that xanthan gum decreases the maximum dry density and increases the optimum moisture content. The treated gypseous soils exhibited a low collapse potential by more than 30% - 45% with xanthan gum. The direct shear results of biopolymer treated soils showed significant shear strength gains. The results of the current study imply xanthan gum biopolymer improvement as an environmentally friendly method to improve the engineering properties of gypseous soil.

Gypseous soil is a metastable soil that causes problems in the constructions built on it under wetting conditions. Due to the harmful effects of traditional soil binders such as lime or cement on the environment, alternative environmental-friendly materials have been used to decrease this impact. Casein biopolymer is introduced in this study as a new binder for gypseous soil improvement and milk waste minimizing purposes. The study focused on three primary soil features: compaction properties, shear strength, and collapse potential. These three soil properties are important in the ground improvement techniques. In this study, different casein concentrations were added to the soil with varying gypsum contents. According to the compaction results casein reduces the maximum dry density while increasing the optimum moisture content. Soil treated with casein had a collapse potential of 65–80% lower than untreated soil. The shear strength of casein-treated soil increased significantly in both dry and moist conditions. The current study results suggest the recycled casein as an eco-friendly additive for gypseous soil treatment rather than traditional chemical materials.