2019 Volume 65 Issue 1 Pages 46-53
In order to develop 2-hour-fireproof cross laminated timber (CLT) floor and wall structures, covering them with wood impregnated with fire-retardant agent was studied. In the fire test of the CLT wall specimen, two layers of fire-retardant impregnated wood (Cryptomeria japonica D. Don) were alternately laminated with screws to the load-bearing CLT and a fire test was conducted for 2 hours. The total thickness of the covering material was 90 mm. However, the CLT burned due to early drop-off of the top layer and shrinkage of the second layer, and the wall specimen did not show 2-hour fire-resistance performance. Based on this test result, in the fire test of the floor, the covering material was specified as a fire-retardant impregnated wood panel of three layers of 30 mm thick treated wood and a 10 mm thick untreated wood layer laminated and bonded together with adhesives. The panels were joined by two types of spline made of fire-retardant impregnated wood, and were attached to the CLT with screws. The screw holes were filled with untreated wood. In the 2 hour-fire tests of the floor specimens, flames died out and charring stopped in the covering layer. This result shows that covering with fire-retardant impregnated wood panels makes the CLT 2-hour fireproof.
