Liquefaction Resistance of Biotreated Sand Before and After Exposing to Weathering Conditions

Microbially induced calcite precipitation method is gaining attention as an environmentally friendly method for enhancing the strength and liquefaction resistance of sands as compared to conventional techniques, which are carbon-intensive and cement-based. However, the durability and effect of weathering on liquefaction resistance of biocemented sand are not yet fully explored. Thus, the present study was aimed at investigating the durability of biocemented sand by subjecting the biotreated sand to different weathering conditions, i.e., variable time periods of aging (1.5, 3, 4.5, and 6 months), cyclic freeze-thaw (5, 10, 15, and 20 cycles) actions, and wet-dry (5, 10, 15, and 20) cycles. The biocemented sand biotreated using Bacillus (B.) Sphaericus was tested for ultrasonic pulse velocity (UPV) and unconfined compressive strength to assess durability under different tested conditions. The amount of calcite precipitation was determined, and microstructural changes were also observed through SEM and EDX methods. The liquefaction resistance of biocemented sand was investigated using UPV results and dynamic cyclic simple shear test results. Overall, the results showed up to 2.8 times increase in strength after 6 months of aging, and significant strength with liquefaction resistance was maintained even after 20 freeze-thaw and wetting-drying cycles.