Study on the shrinkage and restrained cracking of concrete with different surface curing methods

The shrinkage of concrete cured with plastic film, controlled permeability formwork liner (CPFL) and moisture retention curing film (MRCF) were experimentally measured using the designed test devices. The compressive strain on the inner surface of steel ring was also studied during the steel ring restrained test. The correlation between the development of shrinkage and strain on the steel ring was analyzed from the perspective of concrete creep. The results show that: The surface curing method has a significant impact on the shrinkage deformation and restrained cracking process of concrete. The curing method should be adapted to the characteristics of the concrete body (w/b), otherwise there will be negative effects. CPFL can effectively reduce the drying shrinkage and the risk of restrained cracking of concrete by reducing the local w/b on the surface of concrete. It has a better effect on the low and medium strength grade concrete (C30 and C50), but has adverse effects on high-strength concrete (C80); MRCF can effectively reduce the shrinkage deformation and the risk of restrained cracking through the water supplement effect of the pre-absorbent materials. It has a better effect on the high-strength concrete, while its effect on low and medium strength grade concrete is relatively small. The creep capacity of concrete is closely related to the relative humidity level. It is stronger during the humidity saturation period, and weaker during the humidity decline period.