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

Abstract

In the last decade, biopolymers have been used as organic soil binders in ground improvement and earthen construction material modification. Although biopolymer-treated soils have substantially enhanced mechanical strength, the deformation characteristics under external loads and material durability (e.g. biodeterioration due to microbial activity) have not yet been fully understood, which limits the in situ practical application of the biopolymer-based soil treatment technology. This study investigated the efficiency of combined carrageenan and casein in strengthening a clayey soil with the biodeterioration consideration. Both mechanical tests (e.g. unconfined compressive strength and one-dimensional consolidation) and biological tests (e.g. high throughput sequencing and rating of mould growth) were conducted. Results indicated that the usage of the carrageenan–casein mixture induced a higher soil compressive strength compared with either carrageen or casein, due to the formation of a three-dimensional gel network. In addition, carrageenan–casein mixture and casein decreased the compressibility of the clayey soil, which might be attributed to the casein’s peculiarity of self-associating into micelles, leading to minimal interactions with water molecules. Carrageenan, due to its affinity for water, increased the soil compressibility. Under the impact of microbial activity, the biopolymer-treated soils underwent deterioration in both surface appearance (i.e. coloured stains and patches caused by mould growth) and compressive strength. A linear relationship was proposed, in which a reduction in compressive strength by approximately 11% is expected while the rating of mould growth is increased by one in a five-rating system. The current research demonstrates that the soil reinforcement with combined carrageenan and casein is able to improve both soil strength and deformation behaviours. It is also suggested to take into account the biodeterioration considerations in the design and implementation of biopolymer-based soil reinforcement practices.

Calcareous silt earthen construction using biopolymer reinforcement

“…It was reported that the theoretical CO2 emission rate is around 0.7 kg/kg for the most common Ordinary Portland Cement (OPC) in China (Nie et al, 2022). Within the few decades, efforts have been paid to promote the reduction of CO2 emissions in construction field by using low carbon materials such as geopolymer (Farooq et al, 2021), biocement (Xiao et al, 2022a) and biopolymer (Ni et al, 2022). Geopolymer works as the cementitious composite in concrete based on the polycondensation of aluminosilicate under alkaline conditions, which has the potential of around 35% CO2 emission reduction than OPC (Farooq et al, 2021).…”

“…In recent years, with the development of extraction and fermentation techniques in chemical and biological engineering, the cost of producing biopolymer decreases hugely (Chang et al, 2020), making its application in the geotechnical field feasible and costacceptable. The representative natural-based biopolymers for soil stabilization can be classified as microorganism-based biopolymers such as xanthan gum and gellan gum, plant-based biopolymers such as guar gum and carrageenan gum, and animal-based biopolymers such as chitosan and casein (Ni et al, 2022). These biopolymers may have different physical and chemical properties due to their differences in molecular structure.…”

“…For the practical use of biopolymer in soil stabilization and earthen construction, the J o u r n a l P r e -p r o o f mechanical properties of biotreated soils were examined. The testing methods involve unconfined compression test (Ni et al, 2022), direct shearing (Chang et al, 2016), static and dynamic triaxial shearing (Noh et al, 2021, Wang et al, 2022, permeability test (Bouazza et al, 2009), soil and water characteristic test (Muguda et al, 2017), model and field scale test (Vydehi et al, 2022). It was shown that the unconfined compression strength (UCS), cohesion, and friction angle can be improved from several to dozens of times via the generation of hydrogen bonds among soil grains, which is mainly dependent on soil type, biopolymer type and content, curing time, temperature (Soldo et al, 2020).…”

“…They showed that the crosslinked specimens show a lower strength degradation rate compared with the pure sample when experiencing dry and wet cycles although the dry UCS is not improved significantly. Ni et al (2022) tried to strengthen soil with J o u r n a l P r e -p r o o f a mixture of Carrageenan and casein. The authors found that the sample with the Carrageenanto-casein ratio of 1:3 exhibited the highest reinforcing ability, which can be attributed to the formation of a network containing both carrageenan helix and casein micelle due to the negative charge of sulphate group in carrageenan chain and the positive charge of the amino acid closing to the surface of casein micelle.…”

Experimental Study of the Usage of Combined Biopolymer and Plants in Reinforcing the Clayey Soil Exposed to Acidic and Alkaline Contaminations

“…In the last decade, a new type of soil reinforcement material biopolymer, which is environmentally friendly and quick-acting, has been gaining an increasing opportunity to be used in the field of geotechnical engineering [1][2][3][4][5][6]. Biopolymer-based soil treatment technology is used to improve the geotechnical properties of soils by adding plant or microbial secretions, as well as some artificially synthesized organic polymers to the soil [7].…”