Enzyme-Induced Carbonate Precipitation Combined with Polyvinyl Alcohol to Solidify Aeolian Sand

Abstract

Enzyme-induced carbonate precipitation (EICP) has emerged as a soil reinforcement technique in recent decades. To enhance the durability of EICP-solidified soil, a method of EICP combined with polyvinyl alcohol (PVA) is proposed to improve aeolian sand. A cementation solution for EICP+PVA was prepared in the PVA solution. Unconfined compression strength, wind erosion, water erosion, and penetration resistance tests were performed to investigate the effect of EICP with different concentrations of PVA (1%, 2%, 3%, 4%, and 5%) on aeolian sand solidification. The durability of aeolian sand solidified by EICP and 3% PVA was examined through freeze–thaw and dry–wet cycle tests. The results demonstrated that the material precipitated from EICP solution is calcite; and that the presence of PVA can improve significantly the unconfined compressive strength, wind erosion resistance, water erosion resistance, and surface strength of EICP-solidified aeolian sand; and that 3% PVA is enough for sand treatment in practical applications. Additionally, EICP+PVA–solidified aeolian sand had high durability to the freeze–thaw and dry–wet cycles. Scanning electron microscopy (SEM) images revealed films with a network structure in the solidified aeolian sand after adding PVA. Combined with the mercury intrusion capillary pressure test, these tests indicated that the improvement of the performance of EICP+PVA–solidified sand mainly was due to the fact that the PVA films enhanced cementation between soil particles and between soil particles and calcium carbonate, and because PVA film–wrapped calcium carbonate filled the large-size pores in the soil.