Effect of surface curing timing on plastic shrinkage cracking of concrete

Surface curing of concrete is known to mitigate potential plastic shrinkage cracking. In this research, water and three curing compounds were used to investigate the efficacy of liquid curing on plastic shrinkage cracking mitigation. Water curing was applied at critical times during the development of plastic shrinkage cracks, namely: the start of capillary pressure build-up, the start of shrinkage, before the first visible surface crack, and during rapid crack growth. The performance of water curing was also compared to a wax emulsion, petroleum-based resin, and water-based acrylic solution curing compounds, all applied at the supplier specified times. Based on the findings of this research, any application of curing helps to relieve the associated potential plastic shrinkage cracking. The optimal timing of water curing application was based on the response of the various mechanisms of plastic shrinkage cracking. Water application at the start of the shrinkage period, about an hour after casting, prevented any shrinkage-related damage and proved to be most desirable. Water curing that was conducted too early or during rapid crack growth was not as effective. The performance of the different curing approaches in terms of settlement, shrinkage, final crack area, and percentage crack reduction was also compared to the uncured reference mix. The curing compounds performed better than water curing, with only the petroleum-based resin curing compound preventing crack formation, i.e. resulting in 100% crack reduction. However, it was concluded that applying water continuously after the drying point is more effective than most curing compounds.