Discussion

Treatment of microbially induced calcite precipitation and Polyvinyl acetate together

The PVAc emulsion is mainly composed of a vinyl acetate (VAc) monomer. VAc can be copolymerized with various monomers, including acrylate, ethylene, vinyl chloride, Veova 10, and methyl methacrylate monomers (Dossi et al., 2010; Sarac and Yildirim, 2006; Rosdi and Ariffin. 2016; Ahmed et al., 2017 ). Such adhesives are used for bonding of wood, paper, and fabric. If PVAc was used for slope treatment, the volume would be large, resulting in higher costs. PVAc emulsions have satisfactory gap-filling properties (Shields 1984 ). Therefore, PVAc and MICP can be used together to bond particles and form a more stable structure, as shown in Fig. 10. With low PVAc concentration, the microstructure forms a network structure (Jaziet al., 2019 ). This decreases the cost by decreasing the required PVAc concentration. In addition, the network structure of PVAc is beneficial to affix the calcium carbonate, which might be a common characteristic for this type of high-molecular polymer. Miao et al., (2019) also reported that Polyacrylamide had the same effect. The structure was confirmed by SEM tests.
During exposure to rainfall, particles are subject to tension and shear forces, which determines the erosion resistance. De Jong et al., (2006) showed that for samples treated with MICP, most of the failure interface was inside calcium carbonate, i.e., the generated calcium carbonate was fractured inside after failure. Therefore, it was necessary to increase the resistance to tension and shear forces. By adding PVAc at low concentration, the network structure can provide stronger resistance to tension or shear force, thus avoiding calcium carbonate fracture