Drying Strategies After Wetting of Cross-Laminated Timber: Effects on Deformation

Abstract

Drying strategies for end-grain-wetted cross-laminated timber (CLT) panels were studied, focusing on deformation development, and the effects of damage to end-grain protection. Deformations were quantiAied using a novel image-processing-based method and manual measurements. CLT test specimens (TSs) with compromised end-grain protection, and without any end-grain protection were put into water contact for 48 and 168 hours. Drying performance was studied under cool conditions (≈12 °C, ≈57 % RH, air circulation only) and under warm conditions (≈23 °C, ≈36 % RH, heating and air circulation). Damage to the end-grain surface protection affecting up to 30 % of the surface area resulted in modest levels of water uptake by mass, but high MC was recorded locally. TSs exposed to water contact for 48 h (MC > 30 % at 10 mm from the end grain) dried to MC < 16 % in 9 days under warm conditions. The TSs exposed for 168 h to water contact (MC > 40 %) required 17 days to dry out. Under cool conditions, the corresponding dry-out times were 21 and 40 days. Only minor differences in drying time were observed between TSs with damaged end-grain protection and unprotected TSs. The deformations detected using the image-processing-based method were up to three times higher in the warm environment compared to cool conditions. Manual point measurements indicated a gap of ≈1.1 mm between CLT lamellas in TSs dried under warm conditions, compared with an average gap of ≈0.5 mm in TSs dried under cool conditions.