Study of hydration behavior of wood cement-based composite II: Effect of chemical additives on the hydration characteristics and strengths of wood-cement composites

Abstract

The influence of the 30 chemical additives on the hydration characteristics of birch wood-cement-water mixture was determined by measuring the maximum hydration temperature (Tmax) and the time (tmax) required to reach the temperature. The chemical additives were tested and divided into two types depending on the pattern of exothermic reaction peak within the 24-h observation period. The wood-cement-water mixtures with additions of each of the 11 type I chemical additives showed a two-peak temperature-time curve similar to that for neat cement. CaCl2, FeCl3, and SnCl2 reached the highest Tmax above 50°C. When the 19 type II chemical additives were included, the mixtures offered only one peak hydration temperature-time curve. Among them, the 10 chemical additives caused an obvious temperature increase at the beginning of the hydration reaction. The most significant effect was with the addition of diethanolamine, where the mixture produced a Tmax above 50°C. The strength values (modulus of rupture, internal bond strength) of word-cement board were tested with separate additions of the 10 chemical additives arranged by the highest Tmax. There was a good positive correlation between Tmax and the strength values. In addition, the composite chemical additives were preliminarily examined to determine if they accelerated the hydration reaction of blast-furnace slag cement. The results revealed that composite chemical additives evidently accelerated the hydration reaction and the setting of blast-furnace slag cement mixed with wood. Blast-furnace slag cement can thus be considered for use as an acceptable inorganic bonding material for wood-cement panel manufacture. © The Japan Wood Research Society 2000.