The main objective of the study was to evaluate the impact of edge bonding technology and different initial moisture content (MC) of lamellas to the air-permeability properties of cross laminated timber (CLT). Hypothesis of the work was that the CLT panels produced with bonded edges and with initially drier lamellas will have smaller air leakage due to smaller possibility of cracking. In addition to initial MC and bonded edges, the number of layers (3 and 5) in CLT panels was also considered. Air leakage and cracks development in CLT panels were measured in surrounding environment with different relative humidity (RH). Panels were conditioned in different steps from humid to dry environment (RH 70%→RH 50%→RH 30%→RH 10%). Panels produced with initially drier lamellas had initial MC close to 6% and with more humid lamellas the MC was about 12%. The results of test showed that he panels with lamellas at lower initial MC had lower air leakage and higher air permeability than the panels with lamellas at higher MC, due to lower shrinkage. In both cycles (long cycle from RH 70% to RH 10% and short cycle from RH 30% to RH 10%) the most airtight panels were 5- layers with bonded edges. Average air leakage of panels without bonded edges was 24% higher than the panels without bonded edges. In crack development, specimen without bonded edges showed a significantly higher increase in both the number of cracks forming and the area covered with cracks after the conditioning of test panels. Specimens without bonded edges the cracks occurred on 0.16mm² per 1.00mm² of panel surface after final conditioning phase. The same value for panels with bonded edges was 0.01mm² per 1.00mm² of surface. Edge bonding technology and use of initially drier lamellas have a significant effect on CLT properties in case where RH in surrounding environment will change by the time of use. Effect on real scale building envelopes made from CLT still needs to be study.
Keywords: CLT, edge bonding, initial moisture content, air permeability, crack development
Authors
Kukk V.
Department of Civil Engineering and Architecture, Tallinn University of Technology, Tallinn, Estonia
Kers J.
Department of Materials and Environmental Technology, Tallinn University of Technology, Tallinn, Estonia
Kalamees T.
Department of Civil Engineering and Architecture, Tallinn University of Technology, Tallinn, Estonia
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