Compressibility and Durability Characteristics of Protein-Based Biopolymer-Amended Organic Soil

The current study investigated the efficacy of a protein-based biopolymer called casein for the modification of the primary and secondary compressibility characteristics and ability to resist sustained moisture attack in organic soils. The dry mixing method was adopted for the tests with dosages of 0.5%, 1%, 2%, and 4% added as a percentage of the dry weight of the soil. Incremental consolidation tests indicated that the compressibility reduced with the inclusion of casein, leading to lower void ratios with an increase in consolidation pressure and casein concentration. The primary compression index ($C_c$) and secondary compression index ($C_{\alpha }$) were reduced by 85% and 67%, respectively, for a 2% casein-soil mix at a consolidation pressure of 100 kPa. The compression ratio ($C_{\alpha }/C_c$) for the 2% treated soil fell outside the range of 0.01, similar to organic soils with fibrous materials. The permeability was reduced with an increase in casein concentration up to 2% (${10}^{-10}\mathrm{m}/\mathrm{s}$) but exhibited a rise at 4% due to the formation of effective flow paths by the formation of inter-aggregate voids. At extended curing periods, the fiber formations contributed to the strength gain in amended soils. However, the successive wetting and drying (w-d) cycles led to fiber detachment and reduced the resistance to moisture attack leading to collapse. The 2%-amended casein-soil mix proved to be most suitable in terms of reduced compressibility and sustained the highest number of w-d cycles. The findings from the current study support the inclusion of casein for short-term applications. The use of this novel material in the ground improvement industry will aid in waste management and recycling, and it can act as a replacement for unsustainable chemical stabilizers such as cement and lime.