Investigations of the optimal requirements for curing of calcium sulfoaluminate cement systems

Wet curing improves ordinary portland cement (OPC) concrete durability and strength by increasing total hydration, densifying microstructure, and decreasing concrete permeability. In general, wet curing is recommended for OPC until it gains >70% of the designed compressive strength, typically for at least 7 days. Calcium sulfoaluminate (CSA) cement may allow for decreased curing time requirements due to its different phase composition from that of OPC, rapid hydration, and strength gain. Rapid hydration may also prevent some disadvantages associated with OPC curing requirements, such as long curing times, costs associated with the use of high-water quantities, and supervision needs for curing processes. In addition, it is important to understand the effect of use of various curing regimes that are currently specified for use with OPC when applied in CSA systems. This study investigated a variety of curing durations and curing solution compositions to understand their effects on CSA hydration, strength development, and shrinkage. The results demonstrate that 3-day moist curing promotes adequate strength gain and completion of hydration reactions. Additionally, wet curing CSA samples even for 1 day led to lower shrinkage than 7-day cured OPC samples and may result in reduced cracking in concrete pavements. Curing through ponding of samples in deionized water or calcium sulfate-saturated solution resulted in strength reductions of 18% or greater relative to fog-curing.