Study on influence of geometric characteristics of cracks on HAM coupling transfer and thermal performance of multi-layer cellular concrete wall

Abstract

The effect of concrete cracks on the evaluation of the thermal performance of walls has not been effectively considered within the assessment of the thermal and hygroscopic performance of buildings. Based on the dual permeability model, a conjugate method is proposed to reconstruct the PDE equation of unsaturated porous materials with cracks. The reliability of the model is verified from three angles: the heat-moisture coupling benchmark of matrix material, the analytical solution of two-dimensional single fracture heat flow coupling problem and the moisture absorption problem of unsaturated cracks. The reliability of the model is verified from three perspectives: the benchmark of thermal and hygroscopic coupling of matrix materials, the analytical solution to the two-dimensional single-break thermal flow coupling problem, and the hygroscopic problem of unsaturated cracks. The effect of heat and moisture transfer in cracked concrete was quantified by detailed modeling of cracks in terms of the probability of over-penetration, crack roughness, crack density, length, and angle of a two-dimensional discrete crack network, showing that cracks contribute to moisture transfer. This is followed by a 10 day experimental simulation of the meteorological environment, comparing the quantities of moisture accumulation, thermal performance, internal surface temperature and humidity within the fractured and non-fractured wall structures, illustrating the potential adverse effects of cracks on thermal performance and moisture transfer in walls under characteristic conditions. Finally, the necessity of applying moisture-proof layer to the damaged wall is demonstrated by comparing the results before and after the application of the moisture-proof layer.