Characterization of Effloresences of Ambient and Elevated Temperature Cured Fly Ash Based Geopolymer Type Concretes.

摘要

Efflorescences formed on the surface of air (ambient) and elevated (70°C) temperatures cured high calcium fly ash based geopolymer type concretes have been characterized by the XRD, SEM-EDX and FTIR techniques. The mineralogical composition of the efflorescence depends on curing temperature. At ambient temperature the main phase of efflorescence consists of atmospheric carbonation product of sodium hydroxide such as thermonatrite (Na_2(CO_3)-H_2O, PDF 8-448), while in the 70°C cured concrete it represents sodium calcium carbonates gaylussite (Na_2Ca(C0_3)_2-5H_2O, PDF 21-343). Mineralogical composition difference between the ambient and 70°C cured concrete's efflolorescences is related to chemical reaction of alkaline liquid with fly ash constituents.