Abstract
Enzyme-induced calcium carbonate precipitation (EICP) technology can improve the strength of treated soil. But it also leads to remarkable brittleness of the soil. This study used polyvinyl alcohol (PVA) fiber combined with EICP to solidify sand. Through the unconfined compressive strength (UCS) test, the effect of PVA fiber incorporation on the mechanical properties of EICP-solidified sand was investigated; the distribution of CaCO3 in the sample and the microstructure of fiber-reinforced EICP-treated sand were explored through the calcium carbonate content (CCC) test and microscopic experiment. Compared with the sand treated by EICP, the strength and stiffness of the sand reinforced by the fiber combined with EICP were greatly improved, and the ductility was also improved to a certain extent. However, the increase of CCC was extremely weak, and the inhomogeneity of CaCO3 distribution was enlarged; the influence of fiber length on the UCS and CCC of the treated sand was greater than that of the fiber content. The improvement of EICP-solidified sand by PVA fiber was mainly due to the formation of a “fiber–CaCO3–sand” spatial structure system through fiber bridging, not the increase of CCC.
Highlights
Microbial-induced calcium carbonate precipitation (MICP) [1] and enzyme-induced calcium carbonate precipitation (EICP) are novel environmentally friendly biogrouting technologies in which EICP technology uses urease directly to induce CaCO3 precipitation, eliminating the tedious microbial culture [2,3]
“Ave” and “average value of CCC (Av)” in Table 4 were taken as unconfined compressive strength (UCS) and calcium carbonate content (CCC) of each group of samples, respectively
UCS TihnetoUcCluSsstetarns,dwarhdicdheavgiagtrioavnawteads tuhseeduntoevreenfledcitstthriebsuttrieonngothf tdhiespfiebresrios,nroesfufilbtienrg‐rienina‐ large forcedamEIoCuPn‐ttroefatCeadCsOan3dp.rTehciepivtaaltuioenaanrdouitnsdsttahnedcalrudstdeervfiiabteirosn[o22f ]UaCnSd ftohruesafcohrmsaimngplaeweak after trreeiantfmorecnetmaernet sahreoaw. nIninfacFti,gausrfieb3e.rSlienncgeththiencirnejaescetido,nthoef pErIoCbPabtirleitaytmofefinbt esrolculutisotenriinng this teisntccrieracsueldat,eadndonthlye speovseintiotinmoefsfi, bcoermcpluasrteedriwngithwtahsethreesfiurlstst toof bFeandgesettroayl.eadn,dwZhhicahoreetduced al. [20t,h21e]a, vtheeracgeemsetnretinnggthefofifctiehnecsyamanpdleUs.CTShheedreisinpearrseiognenaenrdalnlyolno-wun. iformity of soil strength were increased by incorporating fiber, and the strength standard deviation enlarged with increasing fiber length
Summary
Microbial-induced calcium carbonate precipitation (MICP) [1] and enzyme-induced calcium carbonate precipitation (EICP) are novel environmentally friendly biogrouting technologies in which EICP technology uses urease directly to induce CaCO3 precipitation, eliminating the tedious microbial culture [2,3]. Both technologies are widely used in soil reinforcement [4,5,6]. Li et al [9] used a full-contact flexible mold to prepare MICP-treated sand samples with added fiber Their results showed that fiber cooperation can improve shear strength and failure strain. The mechanism of fiber-reinforced EICP may be very different from that of fiber-reinforced MICP, and it had not been found that scholars have carried out this study
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