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.本研究针对以台湾杉（Taiwania cryptomerioides Hay）与稻草为原料、采用二氧化碳注入压制工艺制备的水泥基复合材料，探讨其水化特性及制备工艺参数对材料性能的影响。随后对板材的水化温度、增重率以及物理力学性能进行了对比分析。研究结果表明，料坯的水化温度随台湾杉与稻草的配比、二氧化碳压力、水泥与原料配比以及水灰比（0.25、0.30）的升高而升高。然而，当水灰比超过0.35时，水化温度开始下降；当水灰比超过0.55时，温度下降幅度显著增大，且达到最高温度的时间也明显延迟。这说明适宜的水灰比对该类板材的制备至关重要。因此，可通过水化温度曲线与增重率来筛选水泥基复合材料的最优制备工艺参数。采用二氧化碳注入压制工艺，可在4至6分钟内完成板材成型，所得板材具备良好的尺寸稳定性，其静曲强度（MOR）介于34.83至57.09千克力/平方厘米之间。本研究对比了三个变量对板材性能的影响权重，其中原料配比对板材性能的影响最为显著，其次为水泥与原料配比，最后为制备时长。当采用50%台湾杉与50%稻草的原料配比，且水泥与原料配比为3.0/1、3.5/1、4.0/1时，所得水泥基复合材料在可燃性、产热量及发烟因子方面均表现出优异的性能。但当板材的续燃时间超过30秒时，仅能达到CNS-6532标准的三级合格要求，仍需开展更多研究以实现性能的进一步优化。