A Primary Study on Mechanical Properties of Heat-Treated Wood via in-situ Synthesis of Calcium Carbonate

This study aims to improve the value of fast-growing wood and extend the heat-treated wood utilization using inorganic calcium carbonate (CaCO 3 ) crystals via an in-situ synthesis method.CaCl 2 and Na 2 CO 3 solutions with a concentration ratio of 1:1 were successively introduced into the thermally modified poplar wood obtained by steam heat treatment (HT) at 200°C for 1.5 and 3 h, resulting in the in-situ synthesis of CaCO 3 crystals inside the heat-treated wood.The filling effect was best at the concentration of 1.2 mol/L.CaCO 3 was uniformly distributed in the cell cavities of the heat-treated wood, and some of the crystals were embedded in the fissures of the wood cell walls.The morphology of CaCO 3 crystals was mainly spherical and rhombic polyhedral.Three main types of CaCO 3 crystals were calcite, vaterite, and aragonite.The HT of poplar wood at 200°C resulted in degrading the chemical components of the wood cell wall.This degradation led to reduced wood mechanical properties, including the surface hardness (HD), modulus of rupture (MOR), and modulus of elasticity (MOE).After CaCO 3 was in-situ synthesized in the heat-treated wood, the HD increased by 18.36% and 16.35%, and MOR increased by 14.64% and 8.89%, respectively.Because of the CaCO 3 synthesization, the char residue of the 200°C heat-treated wood samples increased by 9.31% and the maximum weight loss rate decreased by 19.80%, indicating that the filling with CaCO 3 cannot only improve the mechanical properties of the heat-treated wood but also effectively enhance its thermal stability.