Moisture induced stresses in cross laminated timber (CLT) made from hydrothermally modified wood

In the current research work, moisture gradients and moisture induced stresses (MiS) were investigated in cross laminated timber (CLT) bearing hydrothermally treated fir wood in its outermost laminations. Wooden blocks were cut from fir wood planks and hydrothermally treated in a stainless-steel reactor at 170 °C for a holding time of 30 min. The panels were made with combinations of untreated and treated wood with one as well as two treated layers laid up on both sides of the CLT samples. Afterwards, the CLT panels were exposed to drying (from RH 88 to 32%) and wetting (from RH 32 to 88%) cycles to provide moisture gradients as well as moisture induced stresses. The results showed that higher moisture gradients and moisture induced stresses were recorded on the untreated panels. It was revealed that the moisture gradient due to wetting and drying cycles was reduced because of the hydrothermal treatment of wood.