Effect of early-age loading, formwork removal time, and curing method on the cracking behavior of hydraulic lining concrete structures: Experimental analysis and multi-scale coupling cracking analysis model

Abstract

Beginning at the casting stage, factors such as excessive early-age loading, early removal of the formwork, and unfavorable temperature–humidity conditions can negatively affect the mechanical property evolution of hydraulic lining concrete. Structurally, these factors exacerbate the development of tensile stresses within the lining. When the tensile stress exceeds the tensile strength of the concrete, cracking occurs. To investigate the multi-scale cracking mechanisms in hydraulic lining concrete structures, this study designed a loading apparatus for lining concrete members. Experiments were conducted with early-age loading, formwork removal time, and post-removal environmental temperature and humidity as test variables. The results indicate that early-age loading enhanced the tensile strength of the concrete, delayed cracking time, and increased the cracking load. Advancing the formwork removal time to one day accelerated the development of tensile stresses, causing cracks to propagate throughout the surface. Moisture-retaining curing after formwork removal both improved the development of tensile strength and mitigated the evolution of tensile stress, thereby preventing crack formation. Based on the experimental findings, a multiscale coupled model that integrates compaction and damage effects was employed to establish a quantitative approach for assessing cracks in lining concrete structures, accounting for the evolution of concrete properties. The multiscale model was extended from the material level to the structural level, enabling numerical simulation of the cracking behavior of lining concrete during construction. This provides a finite element-based predictive approach for preventing lining cracking in engineering practice.