低温烧结蚌壳改性粉煤灰水泥基材料水化机理分析

Hydration mechanism of fly ash cement-based material modified by clam shell sintered at low temperature

鉴于粉煤灰和废弃蚌壳对环境的污染,研究了将二者复合用作水泥砂浆掺合料的可行性。通过对蚌壳进行研磨过筛处理,粒度控制在124μm左右,对比分析了不同温度烧结后蚌壳粉与室温蚌壳粉对水泥砂浆性能的影响,确定了蚌壳的适宜烧结温度和掺量。采用X射线衍射(XRD)、扫描电镜(SEM)和热重-差热分析(TG-DTA)等手段对烧结后蚌壳粉改性砂浆水化机理进行了深入分析。研究表明:磨细蚌壳粉经850～900℃烧结后,掺量为3%时对粉煤灰水泥基材料的激发作用最显著,能促进水泥复合胶凝体系的水化,生成大量水化硅酸钙凝胶(C-S-H)和钙矾石(AFt)等水化产物,蚌壳粉改性水泥砂浆的3 d、28 d抗压强度较空白砂浆均有所提高,改性后水泥砂浆具有良好的力学性能。

In view of the environmental pollution resulted from fly ash and clam-shell wastes, the feasibility of using the admixture of these two by-product and waste in cement mortar was studied. By grinding and screening, the fineness of the clam-shell powder was controlled at about 124μm. Effects of clam-shell powders un-sintered and sintered at different temperatures on performance of the cement mortar were compared. The proper sintering temperature and addition amount of clam-shell powder were determined. Hydration mechanism of the modified mortar was further studied by X-ray diffraction （ XRD）, scanning electron microscopy （SEM） and thermogravimetry -differential thermal analysis （TG-DTA）. The results show that finely ground clam-shell powder sintered at 850-900℃ with addition amount of 3% improved performance of fly ash cement-based material signifieantly. The finely ground clam-shell promoted the hydration of the complex cementing system, and generated more C-S-H gel, ettringite and other products. Compared with the blank mortar, the compressive strength of the modified mortar at ages of 3 d and 28 d increased. The modified cement mortar had good meehanieal properties.