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

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.