Influence of Slag Aggregate Production on Its Potential for Use in Internal Curing

Internal curing is effective at reducing shrinkage and early-age cracking in cementitious systems with low water-to-cementitious materials ratios. In the United States, internal curing is typically accomplished using prewetted lightweight aggregate made by expanding slate, clay, or shale. This research focused on the use of porous slag aggregate, a byproduct of the iron and steel industry, for the internal curing of concrete. Five aggregates were evaluated for use in internal curing. The aggregates were produced from different manufacturing processes. Expanded, pelletized, and air-cooled slag aggregates were chosen for advanced testing. The research began by measuring the absorption and desorption properties of the aggregates. Laboratory testing of concrete mixtures containing select aggregates was performed to evaluate mechanical and durability properties. Full-scale testing was carried out with concrete produced at a ready-mix plant. A conventional department of transportation bridge deck mixture was compared with a similar concrete that was internally cured with prewetted expanded slag aggregate. Internally cured concrete made with expanded slag aggregate was shown to reduce shrinkage cracking with similar or improved overall mechanical and durability properties when compared with the conventional mixture.