Parameter Analysis of Optimal Temperature and Humidity of Ultra-High-Performance Concrete During Curing Stage

A bridge deck in the negative-moment zone of a steel-concrete composite beam is prone to cracks in the actual operation stage, even if a high-performance material such as ultra-high-performance concrete (UHPC) is used. This study aims to enhance the cracking resistance of UHPC by optimizing the curing parameters, specifically temperature and relative humidity, to improve the strength and durability of bridge deck in the negative moment zone of steel-concrete composite beam. Drawing from the analysis of heat-transfer modes, including conduction, convection, and radiation, as well as their applications in various contexts, the general forms of temperature and relative-humidity field control equations are studied, and a heat-and-relative-humidity coupled-control model is proposed. The equivalent-temperature method is adopted to analyze the coupling effect of temperature and relative humidity. The analysis results indicate that the equivalent stress and deformation of UHPC exhibit a quadratic parabolic relationship with temperature and relative humidity during the curing stage. Furthermore, the optimal control temperature for UHPC is determined in two different temperature and relative-humidity environments during the curing stage. These parameters can be used as the optimal settings for the construction stage.