Cross laminated timber (CLT), also known as “Engineered wood” developed initially in Europe (Switzerland) in early 1990s and it is designed mostly for multistorey buildings as load-bearing elements because of its versatility compared with other timber products such as glue laminated timber. This research is focused on the problem of cracks formation caused by moisture movement during initial ser- vice period of CLT panel and its impacts to panel’s hygrothemral performances. Due to that following main objective was set: to evaluate the impact of presumably set cracks to CLT panel’s performances of water vapour resistance. Simulated cracks impact to water vapour resistance was examined in this research through scientific experiment. Experiment was carried out by “Cup test” accordance to standard ISO/DIS 12572 and specimen types what were used for experiments were plane-glued solid wood panels (two layers) from which two were with drilled hole with diameter of 2 and 6 mm for simulating cracks. Specimens were placed between almost 0% (inside the cup) and 50% (surrounding environment achieved by climate chamber) of relative humidity (RH). Almost 0% of RH was achieved by CaCl2. Results were recorded by weighing the cups after each 72 hours and test ended when change of cup weight stayed constant. Results showed that the mean value of water vapour resistance factor µ of plane-glued solid wood panels was about 286, specimens with 2 mm diameter hole was 259 and with 6 mm diameter hole was about 198. From analyses of the results it was found that the impact of crack growth between 2 and 6 mm diameter simulated cracks in CLT panels is considerable to water vapour resistance of panels. Crack with diameter of 2 mm decreased water vapour resistance of CLT panel about 9% and 6 mm diameter crack decreased 30 % of resistance. For further studies it was proposed to study possible effects of decreased of water vapour resistance in cracks location to CLT panels in wall assembly.
Keywords: Cross laminated timber, cracks formation, water vapour resistance
Authors
Kukk V.
Department of Polymer Materials, Tallinn Univesity of Technology
Püssa M.
Department of Polymer Materials, Tallinn Univesity of Technology
Kallakas H.
Department of Polymer Materials, Tallinn Univesity of Technology
Kers J.
Department of Polymer Materials, Tallinn Univesity of Technology
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