Analysis of curing conditions effect on refractory calcium aluminate phosphate cement and concrete hydration (review)

Abstract

A literature review and analysis of the effect of curing conditions on refractory calcium aluminate phosphate cement and concrete (CAPC) hydration were conducted. It was shown that temperature, as well as H2O requirement, are the most important variables requiring control during the installation of refractory­concrete linings because it influences the sensitivity of these materials to all processing steps including mixing, placement, curing, and heatup. The above requirements have a sequential effect on the service life and performance of a refractory­concrete lining bonded with CAPC; that is, the strength degradation resulting from structural defects caused by improper placement will be amplified by the use of poor curing practices and of nonuniform and excessively rapid heating. The processing variables that must be controlled during installation and initial heatup of CAPC­bonded concretes are H2O requirement; placement method; curing time, temperature, humidity; and heating rate and schedule. It was shown how the resultant hydrated CAP phases contribute to developing hydraulic bonds at ambient temperatures. It emphasizes the correct use of curing, drying, and firing procedures to avoid structural defects relating to the transition of hydrated phases and gels. Permeable crystalline phases are then developed that maximize structural stability and ensure safe heating of monolithic linings. The concretes obtained retain their volume integrity when subjected to prolonged periods of cyclic heating and cooling; can be used for refractory applications at 1700 °C exhibit sufficient strength of lining 40 MPa.