Experimental Research on Moisture Transfer, Burning and Charring Behavior of Glue Laminated Larch Under Fire Heating Using Cone Calorimeter

Cone calorimeter tests were conducted to investigate the moisture transfer, burning and charring behavior of timber under fire heating. 99 × 99 × 50 mm glue laminated larch specimens were made in cross grain and straight grain directions. The initial average moisture contents were 15.1 wt. % (cross grain specimens) and 13.5 wt.% (straight grain specimens). Twenty specimens were heated at 50 kW/m² of irradiance. Heating duration was varied between 10 to 50 min. Internal temperatures, surface temperature, heat release rate, and moisture contents were measured during heating. Charred depth, colored depth and burnt-out depth was measured after cooling. Heat release rate was measured by oxygen consumption method. Temperature was measured by an IR camera and thermocouples. Moisture content was measured by the electrical resistance method. Charring and coloring temperatures were estimated by using the measured charred or colored depth data and temperature histories. Burnt-out depth, charred depth and colored depth were slightly larger in case of straight grain specimens than that in cross grain specimens. Heat release rates were almost constant after reaching the first peak values. Temperature creep was observed in each location at about 100°C, according to evaporation of water. Maximum internal temperature of each specimen at each location increased while heating duration increased. Peak value of moisture content varied by each specimen, but the temperatures corresponding with peak moisture content were almost the same, i.e., around 100°C to 120°C. Moving speed of moisture peak is about 1.30 mm/min. Charring and coloring temperature were about 380 and 260°C, respectively.