Manufacture of Cement-bonded Boards from Wood and Other Lignocellulosic Materials: Relationships between Cement Hydration and Mechanical Properies of Cement-bonded Boards

摘要

The hydration temperatures of mixtures of cement, additives and powders of sugi (Cryptomeria japonica D. Don), hinoki (Chamaecyparis obtusa Endl.), bamboo (Phyllostachys heterocycla Mitf. var. pubescens Ohwi), kenaf (Hibiscus cannabinus L.), rice hull or rice straw were measured. The total energy released (ET) during hydration was calculated from the area enclosed by the time-temperature curves of the mixtures at room temperature. The bending strength (MOR, MOE) of cement-bonded boards (CBB) made from the materials were tested according to Japanese standard J1S A 5908. Cured specimens from the CBB were analysed using x-ray powder diffractometry (XRD) and TG-DTA to determine the degree of hydration of cement in the CBB. There were correlations between the mechanical properties of bamboo CBB and the XRD intensity of the cement clinker and C_3S, the weight losses at 200℃ and 900℃ under TG-DTA, and the estimated yield of Ca(OH)_2. From these relationships, the mechanical properties of bamboo CBB containing carbonates as additives can be predicted. Depending on the raw material, the MOR and MOE of CBB can also be predicted from the total energy released by mixtures of cement and powdered samples from the same raw material. This can be applied to predict the strength of CBB where the degree of hydration is the dominant factor affecting strength.