Numerical simulation of CLT moisture uptake and dry-out following water infiltration through end-grain surfaces

Abstract

Cross-laminated timber (CLT) offers the potential to construct advanced load-bearing walls and floors made of wood, as its larger dimensions and homogenized material properties expands the application possibilities. As for wood in general, CLT can be negatively affected by moisture. End-grain wetting of CLT coupled with conditions that trap moisture can be particularly problematic due to hindered drying. However, CLT end-grain wetting and subsequent moisture dry-out are hardly investigated and conventional models have not been able to simulate these conditions sufficiently. Here, we show that the moisture uptake and dry-out under this unfavorable condition can be realistically simulated using a moisture transport model including free water. We modeled a basic configuration of one-week wetting, followed by two weeks of dry-out in different climatic conditions. To refine the simulations, the mass transfer coefficients of water vapor and free water were calibrated. In a sensitivity analysis, the influence of both coefficients on moisture development was investigated, revealing that the most significant effect on moisture changes originates from the mass transfer coefficient of free water. Furthermore, the influence of glue lines connecting the layers of CLT panels on moisture transport was examined. The results suggest that the glue line has a minor influence on the moisture behavior of CLT surface layers, but the effects increase towards the middle layer.