Comparison of Chemical Source and Microbially Produced Ferrous Cations for Iron-Based Biocementation of Sand

An alternative approach in soil improvement techniques is to use microbial processes to improve the engineering properties of soil called microbial geotechnology. In addition to the use of calcium-based biocement, a new variation in biocement through the microbially induced iron salts precipitation was also considered. The present study discussed the feasibility of iron-based biocement using two methods: (1) chemical source and (2) microbially produced ferrous cations. Hence, innovative biocement production by the addition of urea and ferrous cation solutions after the application of urease-producing bacteria to sand samples was carried out, and the possibility of increasing the shear strength of soil was explored. Results show that increasing the precipitated cation-to-sand ratio of 6 % (w/w) resulted in a significant increase in the UCS value up to 402 kPa. Precipitation of iron salts was seen between sand grains in the soil microstructure analysis. Simultaneously, other applications of iron-based biocement for soil improvement such as bioclogging in sand and their feasibility in the field require further investigation.