Study on manufacturing functional composite cement boards and analyses of the VOCs from interior environment. (3/3)

To the thinned logs of Taiwania cryptomerioides and non-wood particle raw materials, we added bamboo charcoal (moso bamboo charred at 850℃) and mixed with Portland cement and using the carbon dioxide injection pressing technique to form functional composite cement board quickly. The forming experiments consisted of 2 parts, firstly, the 4 variables (water to cement ratio, cement to particle ratio, pressure of carbon dioxide and forming time) combined for 16 experimental conditions. Then we measured the hydration temperature and weight gain of each condition to determine the optimal range of board forming and formed boards accordingly. The electromagnetic shielding characteristics, static bending strength and incombustibility property of the boards were then measured. In addition, we examined means of reducing volatile organic compounds (VOCs) in wood construction. The method entailed collection VOC samples with sorbent tubes and the Tedlar bags, then using the preconcentration/gas chromatograph to analyze the compounds contained therein.
Agricultural residual material, specifically rice straw was used for hydration experiment. The most important board forming parameter was water to cement ratio, when it exceeded 0.4, the hydration temperature decreased. When it reached 0.50, the hydration temperature lowered drastically. Hence, we’ve determined the optimal ratio to be 0.35. Maximum hydration temperature of 87.2℃ was then reached. The higher the cement to rice straw ratio, the greater the increase in hydration temperature was. With increased injection pressure, board forming time was shortened. When bamboo charcoal was added to the boards, the insertion loss value decreased with increasing charcoal content and board thickness, whereas the return loss value showed an opposite trend. Thus bamboo charcoal was conducive to the enhancement of the electromagnetic shielding characteristics of the boards. Forming boards at different conditions affected board strengths and the cement to particle ratio was the most important variable, it was followed by particle to bamboo charcoal ratio, while forming time had the least effect. We collected ambient air in a saw mill sawing China fir logs using Tedlar bags. The air after preconcentration was analyzed in a gas chromatograph. The results indicate that in the saw mill air, there were α-pinene, camphene,β-pinene, myrcene,α-terpinene, 3-carene, terpinolene etc.

以台湾杉（Taiwania cryptomerioides）间伐原木与非木质颗粒原料为基底，添加毛竹基竹炭（moso bamboo charred at 850℃），与硅酸盐水泥（Portland cement）混合后，采用二氧化碳注射压制成型技术（carbon dioxide injection pressing technique）快速制备功能性复合水泥板（functional composite cement board）。成型实验分为两部分：首先设置4个变量，即水灰比（water to cement ratio）、水泥-颗粒比（cement to particle ratio）、二氧化碳压力、成型时间（forming time），组合得到16组实验工况；随后测定每组工况的水化温度与增重率，以此确定板材成型的最优区间，并依此制备复合水泥板。随后对板材的电磁屏蔽特性、静曲强度与不燃性能进行测试。此外，本研究还探究了木材建筑中挥发性有机化合物（volatile organic compounds, VOCs）的减排方法：采用吸附管（sorbent tubes）与泰德拉采样袋（Tedlar bags）采集VOC样品，通过预浓缩-气相色谱联用仪（preconcentration/gas chromatograph）对其中的有机成分进行分析。
本实验采用农业废弃物稻草（rice straw）作为原料开展水化试验。板材成型的关键参数为水灰比：当水灰比超过0.4时，水化温度开始下降；当水灰比达到0.50时，水化温度大幅降低。据此确定最优水灰比为0.35，此时水化温度最高可达87.2℃。水泥-稻草比越高，水化温度的升幅越大；注射压力越高，板材成型所需时间越短。向板材中添加竹炭后，插入损耗（insertion loss）值随竹炭掺量与板材厚度的增加而降低，而回波损耗（return loss）值则呈现相反的变化趋势，表明竹炭有助于提升板材的电磁屏蔽特性。不同成型工况对板材强度均存在影响，其中水泥-颗粒比为最关键的影响变量，其次为颗粒-竹炭比，成型时间的影响程度最小。本研究采用泰德拉采样袋（Tedlar bags）采集了某锯切杉木（China fir）原木的锯木厂车间环境空气，经预浓缩后通过气相色谱仪分析，结果显示锯木厂空气中含有α-蒎烯（α-pinene）、莰烯（camphene）、β-蒎烯（β-pinene）、月桂烯（myrcene）、α-松油烯（α-terpinene）、3-蒈烯（3-carene）、松油烯（terpinolene）等挥发性有机物。