Development of a Rigid Full-Contact Mold for Preparing Biobeams through Microbial-Induced Calcite Precipitation

As a new environmentally friendly and sustainable technique for soil improvement, microbial-induced calcite precipitation (MICP) has been studied widely. A suitable sample preparation mold is the first step to prepare MICP treatment. The purpose of this study is to develop a rigid full-contact mold to prepare larger biobeam specimens for MICP treatments with an immersing method. Four different molds were developed, including a plastic beam rigid mold without a cover, a full-contact flexible mold, a rigid full-contact mold with geotextiles, and a rigid full-contact mold with filter paper. Beam-shaped specimens with different dimensions were treated with the four molds in the MICP process. A four-point bending test and a split tensile strength test were conducted to evaluate the flexural behavior of MICP-treated specimens from the four sample preparation molds. The results indicated that an MICP-treated sample prepared by the rigid full-contact mold with geotextiles can form the best beam shape and the most uniform calcite precipitation inside the sample. Additionally, the biobeam made by the rigid full-contact mold with geotextiles achieved the best mechanical properties. The flexural strength of the biobeam made by the rigid full-contact mold was 1,125 kPa at a failure flexural strain of 1.5 %, and the split tensile strength was 368 kPa with a failure tensile strain of 1.8 %.