Plastic or early-age shrinkage cracking remains a critical concern for cement-based repairs and overlays. There are several reasons for this concern: First, for a better bond, cement-based repair materials generally carry large amounts of cements which increases the overall shrinkage; second, the substrate offers a high level of restraint, thereby increasing the possibility of developing tensile stresses sufficient to cause tensile cracking in the overlays; and finally, it is often difficult, if not impossible, to properly cure repair materials. Cracking, if it occurs, negatively affects the durability of both the repair material and the substrate and allows the ingress of deleterious chemicals that damage and weaken the interface and promote rebar corrosion. Apart from repairs and patching, early-age shrinkage cracking remains a concern for numerous other large surface area placements including slabs-on-grade, tilt-up-construction, precast panels, and shotcrete linings.
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