Manufacture of Bamboo-Cement Composites VI. Effects of silica fume addition and heat-treatment on properties of hot-pressed boards

In the previous paper, it was proved that cement-bonded bamboo composites ( CBC) can be manufactured in a short press time with the addition of Na2SiO3 and hot-pressing. The present paper concerns the improvement of the proces s by additional heat treatments combined with the addition of silica fume t o further shorten the CBC curing time. The effects of the addition of silic a fume, heat-treatment temperature and time, effect of hot-press time on th e degree of cement hydration and the properties of CBC, are discussed. The hydration degrees of the composites were examined by X-ray diffraction (XRD ), scanning electron microscope (SEM), and thermogravimetric differential t hermal analysis (TG-DTA). The results were as follows: 1) CBC properties we re improved with additional heat treatment, especially with the combination of heat treatment and the addition of silica fume. 2) In the case of using additional heat treatment, the optimum amount of addition of silica fume w as 5%. The cured structures were more compact at a 5% addition of silica fu me and the interface between bamboo and cured cement might have been improv ed. 3) CBC properties were improved markedly at a heat treatment temperatur e of 100 degrees C than those at 60 degrees C and 80 degrees C. 4) The long er hot-press time resulted in better mechanical properties of CBC. The fina l properties of CBC were related to their initial strength and hydration de gree (strength and hydration degree, respective ly, immediately after hot-p ressing). The optimum condition of CBC manufacture were : the addition of 1 5% Na2SiO3 and 5% silica fume, Ii-min hot-pressing at 110 degrees C, 24 hr heat treatment at 100 degrees C.