Characteristics of Taiwania/Rice straw Composites Boards with Cement by CO2 Injection for Rapid Production.

Hydration characteristics and effect of manufacturing conditions on the properties of cement bonded composites made from Taiwania cryptomerioides Hay and rice straw by CO2 injection pressing technique. The hydration temperature, percent weight gain and physical and mechanical properties of the boards were then compared. The results show that the hydration temperature of the mat increased with increasing Taiwania to rice straw ratio, carbon dioxide pressure, cement/material ratio and water/cement ratio (0.25,0.30). However, when the water/cement ratio exceeded 0.35 the hydration temperature started to drop, and the drop was increased significantly when the ratio exceeded 0.55 and the time to reach the maximum temperature also markedly delayed. This indicate that appropriate water/cement ratio is very important for the boards manufactured. Therefore, hydration temperature curves and percent weight gain could be used to select optimum conditions for the manufacturing of cement bonded composites. By means of the carbon dioxide injection pressing process, the boards could be formed within 4 to 6 minutes. manufactured with good dimensional stability, MOR of the resulting boards ranged between 34.83 and 57.09 kgf/cm2. Comparing the importance of the 3 variables of this study, the material ratios had the greatest influence on the board properties, followed by cement/material ratio, and manufacturing time. Manufactured with the proportion of 50% Taiwania and 50 % rice straw and the cement/material ratio 3.0/1, 3.5/1, 4.0/1, cement bonded composites had achieved good quality in ignitability, heat generation and fuming factor. However, the afterflaming time of the boards longer than 30 sec made the boards only qualified by the Grade 3 standard of CNS-6532, which needs more researches for further betterment.