Evaluating Full and Partial Internal Curing in Terms of Internal Relative Humidity, Hydration and Performance

Abstract

Internal curing is being increasingly considered for use in concrete pavements. Internal curing frequently uses prewetted lightweight aggregate (LWA) to provide water to the cement paste as it hydrates. While internal curing has many benefits, many of these benefits can be traced to the additional hydration or a reduction in autogenous shrinkage that occurs as a result of the water that is stored in the aggregate. Many times internally cured mixtures are designed to provide a volume of internal curing water that is equivalent to the volume of chemical shrinkage; some have asked if there are benefits to only supplying a portion of this water. If only a portion of this water is needed it would reduce the volume of LWA used and make the pavement more cost-efficient. This paper examines the additional hydration that occurs in internally cured concrete systems with varying levels of internal curing (i.e., varying volumes of water that are equal to chemical shrinkage as well as partial volumes of this water) at early ages using isothermal calorimetry. In addition, internal relative humidity and the densification of the ITZ are measured for the plain and internally cured concrete. Internal curing is beneficial as the additional hydration can improve strength and reduce fluid transport. Internal curing, relative humidity, cement hydration, degree of hydration, calorimetry, SEM, Scanning Electrical Microscopy