Abstract
The shrinkage and steel ring restrained cracking process of concrete using plastic film (PF), controlled permeability formwork liner (CPFL) and moisture retention curing film (MRCF) were experimentally measured using the designed test devices; A two-stage model for concrete creep considering humidity levels was established and the creep parameters were calibrated based on experimental results under sealed conditions; The uniform compressive stress of steel ring was calculated using the above model when the concrete using PF, CPFL and MRCF three different curing methods. The experimental and theoretical 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 and forming a dense protective layer. 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 of concrete 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 two-stage creep model of concrete can better describe the differences in creep effects of concrete under different humidity levels. And the effective stress of the steel ring restraint concrete under different curing methods was accurately calculated using the model.