Engineering Properties of MICP-Bonded Sandstones Used for Historical Masonry Building Restoration

Compared to many other cemented geo-materials, such as concrete and natural limestone or sandstone sediments, the applications of microbial induced carbonate in-situ precipitation (MICP) bonded sandstones by Sporosarcina pasteurii in many civil strengthening works were limited due to their low strength. The established empirical correlation of the compressive strength parameter and the MICP yield was not satisfactory since little validation data was reported for the uniaxial compressive strength higher than 8∼10MPa. The present study was focused on producing MICP bonded sandstones under laboratory and field conditions with the high strength using advanced material and biological science approach. According to the previous studies carried out at Tsinghua University, the continuous 4 weeks biological treatment with the enzyme activity about 18mM urea hydrolyzed per min could lead to the cubic sandstone with the uniaxial compressive strength (UCS) no more than 5MPa. Coarse-grained and fine-grained sands were used, but little strength gain was observed. Strength improvement technologies were considered and investigated including the in-situ supply of cultivation culture and optimization of grouting route.