Field Considerations for Calcium Chloride Modification of Soil-Cement: Fid-Bau Portal

Field Considerations for Calcium Chloride Modification of Soil-Cement

Bowers, Benjamin F. / Daniels, John L. / Anderson, J. Brian

Calcium chloride ( ${CaCl}_{2}$ ) has been used to accelerate strength gain in soil-cement mixtures. While its use in concrete is well established, there are few reports on dosage and temperature controls in soil-cement applications. This article provides laboratory and field data regarding the unconfined compression (UC) strength of soil-cement as a function of temperature, time, and dosage. The results indicate ${CaCl}_{2}$ can increase the UC strength of soil-cement mixtures at curing temperatures of 2°C and 21°C while decreasing it dramatically if the initial temperature exceeds 50°C. At a 2°C curing temperature, a dosage of 1% ${CaCl}_{2}$ (by weight of cement) increased the average 28-day UC strength from 1,618 to 1,869 kPa ( $+ 15.5 %$ ) while at 21°C the strength gain was significant at a dosage of 5% ${CaCl}_{2}$ , increasing the average 28-day UC strength from 1,916 to 2,338 kPa ( $+ 22.0 %$ ). In general, there is an optimum dosage that varies with temperature and soil type. In terms of field application, it is possible to use conventional construction equipment to wet dose ${CaCl}_{2}$ without raising the moisture content by more than 1.5%, a key consideration when in situ conditions are wet relative to target moisture conditions. For the soils tested, the optimum dosages are expected to be closer to that which is specified for cold-weather concreting (e.g., $< 2 %$ by weight of cement), rather than much higher values reported in the literature.