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