Non-microbial carbonate precipitation as an improvement technique of sand

In this study, the formation of artificial Calcium Carbonate (CaCO3) from the reaction between Calcium Hydroxide (CH) and Carbon Dioxide (CO2) was taken into account to improve sand properties. Firstly, Jumunjin sand was mixed with 2% of CH and water at a constant water-solid weight ratio of 0.1 before curing in a carbon dioxide chamber. The precipitated calcite content was investigated by the variation of CO2 chamber pressure and number of repeatable treatment. Then, unconfined compression tests of such samples were carried out to evaluate the influence of calcite content on mechanical properties of sand. It indicated that as increasing of repeatable treatment, the UCS of treated sand increased due to the higher of calcite precipitation. The first and fifth cycle do not lead to any significant variations of precipitated calcium carbonate content (CCC) and unconfined compressive strength (UCS) with the change of carbon dioxide chamber pressure from 100 kPa to 200 kPa, but- the higher CCC and UCS can be seen clearly at the tenth cycle. After 10 treated cycles, the UCS of CP1.10 and CP2.10 were 5 times greater than CP1.1 and CP2.1, respectively. The maximum UCS was 361 kPa of CP2.10 specimen. The stress-strain curves obtained from UCS test at 200 kPa CO2 gas pressure exhibited more strain at peak stress than that at 100 kPa and the samples subjected to 10 treated cycles has more ductile behavior than other samples.