煤气化灰渣在水泥与熟石灰中的应用

Application of Coal Gasification Fly Ash in Ordinary Portland Cement and Hydrated Lime

摘要:

对煤气化灰渣（CGFA）在普通硅酸盐水泥（OPC）和熟石灰中的潜在用途及再利用价值进行探讨，包括与聚羧酸高效减水剂的相容性、熟石灰?CGFA体系和OPC?CGFA体系的力学性能。基于X射线衍射（XRD）、傅里叶变换红外光谱（FTIR）和扫描电镜（SEM）研究了2种体系的反应机理和反应产物。结果表明，CGFA的反应性可以通过研磨显著提高，而具有低火山灰反应性的未研磨CGFA可以部分替代混凝土中的天然河砂。熟石灰和OPC可以提供碱性环境以促进地质聚合反应的发生。2种体系试样的28 d最大抗压强度分别达到14.43 MPa（CGFA质量分数60.0%）和35.79 MPa（CGFA质量分数35.7%）。混合物特征峰的强度随着质量分数的增加而降低，表明Ca（OH）₂与CGFA提供的SiO₂发生反应，形成C―S―H。

Abstract:

In this study， the potential application of coal gasification fly ash （CGFA） in ordinary Portland cement （OPC） and hydrated lime is investigated including the compatibility of CGFA and WH-A polycarboxylate superplasticizer and the mechanical property of hydrated lime-CGFA and OPC-CGFA systems. Reaction mechanisms and reaction products of the two systems are studied by using XRD， FTIR and SEM. It is found that the reactivity of CGFA in cementitious materials can be considerably enhanced by grinding while the as-received CGFA with low pozzolanic reactivity could be used as sand in concrete. The hydrated lime and OPC provide the alkaline environment to facilitate the dissolution of CGFA. The maximum 28 d compressive strength up to 14.43 MPa （60.0% CGFA） and 35.79 MPa （35.7% CGFA） can be obtained in hydrated lime-CGFA and OPC-CGFA systems， respectively. The intensity of Portlandite peaks decreases with the increase of CGFA mass fraction， indicating that Ca（OH）₂ reacts with SiO₂ provided by CGFA to form C―S―H.