Manufacture of bamboo-cement composites V. Effects of sodium silicate on bamboo-cement composite by hot pressing

Mousou bamboo (Phyllostachys heterocycla Mitf. var, pubescens Ohwi) semi-fl akes were used as raw materials for the manufacture of cement-bonded bamboo composites (CBC) by hot pressing to clarify the effects of pressing temper ature, pressing time, and the additive content of sodium silicate (Na2SiO3) on the degree of cement hydration and on the board properties. The hydrati on degrees of the composites were examined by X-ray diffraction (XRD) analy sis, scanning electron microscope (SEM) observation, and thermogravimetric differential thermal analysis (TG-DTA). The results were as follows: 1) The initial setting of cement was accelerated by hot pressing with Na-2 SiO3 a nd rapid curing of CBC was achieved. The cement hydration was accelerated, and the CBC properties were improved by the addition of Na2SiO3. The optimu m additives content for Na2SiO3 was found to be 15% to 20% based on the cem ent weight. 2) Hot press temperature affected the hydration of cement, and the values of the mechanical properties of CBC pressed at high temperature were greater than those pressed at a low temperature. XRD and TG-DTA analys es showed that the initial setting of cement was slow at lower temperature. Therefore the springback of CBC after pressing was not controlled. Althoug h the hydration of cement was improved by curing under water-soaked conditi on, the mechanical properties of CBC were not enhanced. In the case of CBC pressed at a high temperature (>100 degrees C), the springback of CBC was s uppressed since the initial setting of the cement was accelerated but curin g under water-soaked condition barely improved the hydration of the cement. SEM analysis also showed better structure of CBC pressed at higher tempera tures. 3) Hot pressing time affected the hydration of the cement. In the ra nge from 3 to 21 min, long hot pressing times resulted in improvements of C BC properties.