Technology Administration

The proper curing of concrete is paramount to achieving desired strength and durability performance in the field. Because blending components often react at different rates from portland cement, blended cements may require that special attention be paid to prolonged curing. This report summarizes an exploratory study on the influence of curing conditions on water loss and hydration in ASTM Type I and blended portland cement pastes with a water-cementitious materials ratio (w/cm) of 0.40. The blended cement contains about 20 % by mass fly ash substitution for cement. Water loss/gain under various curing conditions is monitored both globally by bulk mass (loss) measurements and locally using the NIST X-ray absorption apparatus. Hydration is assessed based on the measurement of non-evaporable water content after 31 d of curing. Curing conditions include no curing (exposed to the environment throughout the curing period), sealed curing, and saturated curing for 1 d, 3 d, and 6 d. The cement paste with the fly ash substitution is observed to be more sensitive to curing conditions than the conventional Type I portland cement paste