Amorphous calcium carbonate (ACC) cement for ground improvement

This paper presents a new method of using amorphous calcium carbonate (ACC) cement for ground improvement. Drawing inspiration from the mineralization processes observed in marine organisms, a process has been developed to produce ACC-cement using waste carbide sludge and carbon dioxide. The ACC-cement in the powder form can be mixed with soil and subjected to further microbially induced carbonate precipitation (MICP) process to transfer ACC into other more stable form of CaCO₃ crystals such as calcite. This study showed that by mixing 2.5% (weight to weight) of ACC with sand and subjecting the mixture to a cyclic cementation solution treatment for three days, the compressive strength of treated sand increased to 9 MPa. A microscopic analysis demonstrated the transformation of nano-sized ACC into rounded vaterite, and then rhombohedral calcite that bonded sand grains together to promote effective interlocking between sand particles. The use of ACC also led to a much faster strength gain than the use of cement.