Strength of biocemented coarse sand with kaolin micro-particle improved nucleation

A new treatment, microbially induced calcium carbonate precipitation (MICP) with micro-particle improved nucleation (MICPMPIN), is introduced to improve the performance of MICP technology for the stabilization of coarse sand. A certain amount of kaolin is augmented into the bacterial suspensions to obtain immobilized bacterial slurry, then the bacterial slurry is mixed with cementation solution to form MICP-clay slurry (MICPCS) and percolated through the coarse-sand specimens under gravity. The results show that the unconfined compressive strength (UCS) of MICPMPIN-treated specimens is higher than that of MICP-treated ones. When other conditions are the same, the UCS increases with the increasing dosage of kaolin and volume ratio of immobilized bacterial slurry. The specimens with higher UCS can be obtained by grouting MICPCS every two cycles. The cementation of pure kaolin is so small that the stabilized specimen cannot be a solid. The main contribution for the higher UCS of kaolin is the nucleation that is formed by kaolin, the increment in the amount of effective precipitates, and the decrement in the amount of pore. The wet UCS of the MICPMPIN-treated specimens is larger than that of the conventional MICP treated ones, and the softening resistance is also improved by adding kaolin into the MICP process.