Research on expansion and stability of Friedel’s salt

Friedel’s salt is a common hydrate of cement concrete in chloride environment, and the change of its performance will affect the performance of cement paste and the safety of concrete structure. In order to study the properties and morphological characteristics of Friedel’s salt, Friedel’s salt is prepared by reaction of C3A with chlorine salt and chemical synthesis in this paper. The expansibility and stability of Friedel’s salt are studied by XRD, SEM, TG-DTG and FTIR. The results show that the higher the curing temperature is, the faster the reaction rate is, the expansion degree is 0.3 and the density is 2.087 g/cm3. Friedel’s salt is more stable in alkaline environment, and the greater the pH value is, the more stable the Friedel’s salt is. Under dry heat curing, Friedel’s salt is gradually decomposed with the increase of temperature, and the Friedel’s salt prepared by C3A and chlorine salt is completely decomposed at 500 °C, and the Friedel’s salt prepared by chemical method is completely decomposed at 600 °C. Under damp heat curing, Friedel’s salt is gradually decomposed with the increase of temperature, and it is not completely decomposed at 100 °C.