The study of soil–structure interface behavior contributes to the fundamental understanding of engineering performance and foundation design optimization. The current study results suggest the recycled casein as an eco-friendly additive for gypseous soil treatment rather than traditional chemical materials. The shear strength of casein-treated soil increased significantly in both dry and moist conditions. Soil treated with casein had a collapse potential of 65–80% lower than untreated soil. According to the compaction results casein reduces the maximum dry density while increasing the optimum moisture content. In this study, different casein concentrations were added to the soil with varying gypsum contents. These three soil properties are important in the ground improvement techniques. The study focused on three primary soil features: compaction properties, shear strength, and collapse potential. Casein biopolymer is introduced in this study as a new binder for gypseous soil improvement and milk waste minimizing purposes. 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. Gypseous soil is a metastable soil that causes problems in the constructions built on it under wetting conditions.
More fibers result in more a evident effect of interlacing and bending on sand and higher strength in consolidated sand. (2) The UCS of the different fiber types, from small to large, is basalt fiber < polypropylene fiber < glass fiber < polyvinyl alcohol fiber because the quality of the fiber monofilament differs. The optimal fiber length of polypropylene, glass, and polyvinyl alcohol fiber is 9 mm, and that of basalt fiber is 12 mm. However, the agglomeration caused by overlong fibers leads to uneven distribution of calcium carbonate and a reduction in strength. Results show the following: (1) The unconfined compressive strength (UCS) of MICP-treated sand first increases and then decreases with increasing fiber length because short fiber reinforcement can promote the precipitation of calcium carbonate, and the network formed between the fibers limits the movement of sand particles and enhances the strength of the microbial solidified sand. In this paper, we analyze the impact mechanism of fiber type and length on the immobilization of microorganisms from macroscopic and microscopic perspectives with fibers of 0.2% volume fraction added to microbial-induced calcite precipitation (MICP)-treated sand. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.įibers are applied in construction work to improve the strength and avoid brittle failure of soil. However, this application provides a stable sequestration source for atmospheric CO2 in soil.
This differs from MICP strength improvement of 1000 kPa with 5.3 wt% CaCO3 due to poor binding of sand with the precipitated CaCO3 crystals. Sand pre‐mixed with Ca(OH)2 gave well distributed CaCO3, precipitated throughout the sample with 7.56 wt% and 6.87 wt% CaCO3 content and UCS of 39.2 and 35.3 kPa before failing for batch and continuous flow precipitation respectively. Batch and continuous flow precipitation methods produced a poor distribution of CaCO3, with more CaCO3 precipitated on top, resulting in unconfined compressive strength (UCS) of 6.9 to 19.6 kPa.
Potassium carbonate (K2CO3) was then injected into sand with calcium hydroxide (Ca(OH)2 as a calcium source to precipitate CaCO3 and regenerate KOH. This study utilizes direct air capture (DAC) to absorb atmospheric CO2 using potassium hydroxide (KOH) in a semi‐batch bubble absorption column. This paper proposes using the hydroxide‐based absorption of CO2 instead to provide the carbonate ion source. The microbial‐induced calcite precipitation (MICP) process for ground improvement uses microorganisms to hydrolyze urea, producing carbonate ions to induce in situ calcium carbonate (CaCO3) precipitation in soil to improve its strength.
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