Effects of curing conditions on strength development of controlled low-strength material

The effects of a curing regime on the compressive and splitting tensile. strength of controlled, low-strength material (CLSM) were investigated. Six CLSM mixtures, representing a range of constituent materials and,mixture proportions, wend included in the study. Three curing temperatures, (10, 21, and 38 degreesC) were investigated, and for, each of the curing temperatures, two different relative humidity conditions were used to study the influence of temperature and humidity on strength gain at ages of 7, 28, and 91 days. The effects of temperature and humidity were found to largely depend on the constituent materials and mixture proportioning. In particular the reactivity of fly ash was found to be critical in influencing the strength of CLSM mixtures, especially when an ASTM Class C fly ash was used. Some CLSM mixtures containing Class C fly ash exhibited a significant increase in-strength when cured under the highest temperature condition Although the dependence of cementitious materials containing fly ash on temperature is well known, the increases in strength of CLSM mixtures containing a high-calcium fly ash far exceeded the strength increases typically observed for conventional concrete. CLSM containing fly ash typically has a much higher fly ash-portland cement ratio and as such, the role of fly ash in strength development is significantly increased.