DEVELOPMENT OF HIGHLY DENSIFIED FIBER-REINFORCED CEMENT BOARDS DESIGNED BY PROPER STRUCTURE OF PORES

本财政年度（1997年）的主要研究目标是通过（1）高密度水泥粉粒的致密填充以减少吸水性，和（2）通过碳化作用对无石棉纤维增强水泥板（FRCB）进行化学表面改性以致密材料的表面孔结构，从而提高其抗冻性。为了实现上述目标，采用双级冲击器（DSI）在高速气流中将水泥粉料中的致密颗粒球化，得到高致密水泥生料粉。这种致密的球化水泥粉末使FRCB的吸水率从制造时的15-20%大幅降低到本研究中的4-5%。为了达到上述目的，本文研究了商品FRCB在碱土金属（Ca^+2>或Mg^+2>）溶液中的碳化反应， ...更多信息 在50-60 ℃升温和2-3个大气压CO_2压缩条件下，由于微晶MgCO_3或CaCO_3在FRCB表面的沉淀，使FRCB的致密化。这样的表面碳化使得样品的抗冻性如此之高。目前，Mg^<+2>溶液较Ca^<+2>溶液更致密的碳化作用的优越性仍在从基础无机化学的角度进行研究。用冷却DSC技术测定了水在几种陶瓷氧化物表面的冻结焓和起始温度，从室温到-196 ℃的冻结。作为实验结果，发现来自陶瓷氧化物表面的水结合力随着阳离子和氧原子之间的化学离子键合力的减小而增加。此外，非晶态结构表面的水比结晶良好的表面上的水具有更强的结合力。表面水上的这些结合力的厚度取决于化合物、氧化物的结晶度和疏液性，但粗略估计为约20-30个分子层（即，6-10 nm）。少

The main objectives of the research in this fiscal year (1997) are the enhancement of frost durability of non-asbestos fiber-reinforced cement boards (FRCB) by (1) the densest packing of high densified granules of the cement powder in order to reduce the water absorption, and by (2) the chemical surface modification of FRCB through the carbonation in order to densify the surface pore structure of the materials. For the aim of (1), the high-densified cement raw powder was obtained by the double staged impactor (DSI) which could spheroidize the dense particles from the cement powder mixture in a high speed air vortex. Such a dense spheroidized cement powder made drastically reduced the water absorption of the FRCB from the 15-20% of as fabricated to 4-5% in this research. Such a great decrease in water absorption enabled the excellent improve of frost durability of the FRCB.For the aim of (2), the carbonation of the commercial FRCB being absorbed alkali-earth (Ca^<+2> or Mg^<+2>) solutio … More n under the conditions of warming in 50-60ﾟC and compressing in 2-3 atm.of CO_2 gas enabled denser by precipitation of micro crystalline MgCO_3 or CaCO_3 on the surface of the FRCBs. Such a surface carbonation made the frost durability of the samples so much. Now the superiority of such denser carbonation by Mg^<+2> solution than Ca^<+2> one is now still continuously researching from the fundamental inorganic chemical point of view.For the fundamental research on the mechanism elucidation on frost action of the FRCBs, the thermodynamical stability of water on the surface of several ceramic oxides was compared by cooling DSC technique measuring a freezing enthalpy and an onset temperature in freezing from a room temperature to -196ﾟC.As the results of experiments, it was found that the water bound force from the surface of ceramic oxides increased with the decreases in the chemical ionic bonding force between a cation and an oxygen atoms. And moreover, the water on the surface of non-crystalline structure has much stronger bound force than that on a well crystallized surface. The thickness of these bound force on the surface water depends on a compound, a crystalinity and a lyophobicity of the oxide, but was roughly estimated as about 20-30 molecular layrs (i.e., 6-10 nm). Less