Thermo-Hygro-Mechanical Coupling Model for Early-Age Concrete Based on Microporous Evolution: Analysis of Load Effects on Temperature and Humidity

This study establishes a novel thermo-hygro-mechanical coupling model to analyze load effects on temperature and humidity transmission in early-age concrete, marking the first integration of solid-phase displacement into mass balance equations and quantifying the load-porosity-permeability coupling mechanism. By incorporating momentum balance, mechanical constitutive laws, and thermal-hydro strain relations, the model explicitly addresses porosity variations under loading, adjusts intrinsic permeability coefficients, and resolves the influence of solid-phase deformation on liquid/gas mass transfer. Experimental and numerical results reveal that external loading induces an instantaneous 1%–2% increase in relative humidity, with peak values reached within 4–5 h postloading, while temperature variations remain predominantly governed by environmental conditions. Notably, axial compression reduces porosity by redistributing pore water, increasing saturation, and decelerating moisture transport. The model demonstrates that humidity-load coupling dominates early-age concrete behavior, whereas temperature–load interactions are negligible. These findings provide quantitative insights into pore structure evolution under mechanical stress, offering a refined framework for optimizing curing protocols and durability assessments in structural applications.