Constant Curing Temperature Effect on the Strength of Cement-Treated Soil

The wet method of deep mixing constructs soil-cement columns by mixing soft soil with cement-water slurry to improve the ground. A research project is underway to investigate factors that control the strength of soil improved by cement and to develop a framework for quantitatively accounting for these factors. As a first step of the project, this paper presents unconfined compressive strength (UCS) test results for cement-treated soil with different mix proportions cured at various constant temperatures. A fabricated low plasticity clay (CL) was blended with cement-water slurry and cured in an environmental chamber at low temperatures (–5, 0, and 5°C); other samples were cured inside a temperature-controlled water bath at a high temperature (45°C). Reference samples were cured in a humidity-controlled room at room temperature (21.1°C). UCS tests were conducted on the cured samples at curing times of 3, 7, 14, and 28 days. The test results show that when a curing temperature is 0°C or higher, an increase in temperature increases the strength of cement-treated soil. Furthermore, the strength rapidly increases at early curing stages and slowly increases at later curing stages. The strength development trends are affected not only by curing time and temperature but also by mix proportions. Cement-treated soil with more cement and less water had a concave curve in the curing temperature and UCS relationship, such that strength increases with increasing curing temperature rapidly at a low-temperature range and slowly at a high-temperature range, while a convex curve was observed for the mixture with less cement and more water. At a freezing temperature (–5°C), the strength development with curing time was not remarkable, and strength drops and relatively significant scatters were observed from the mixtures with more cement and less water.