Assessment of the durability of hardening products of modified fly ash cement compositions

This work is devoted to the study of the durability of hardening products of modified gold-cement compositions. The influence of sulfate and carbonate additives of various origins on the kinetics of increasing the strength of artificialstone was studied.To reveal the mechanism of the processes of strength synthesis of the developed binder systems, their hydration products and the composition of new formations were studied using X-ray diffraction (XRD), differential thermal analysis(DTA) and electron microscopy.It was established that with simultaneous modification of the plasticized fly ash cement composition with sulfate and carbonate additives, the synthesis of strength is ensured due to the formation of hydration products in the composition atthe early stages of hardening of ettringite and its analogues containing carbonate and ferric components. It has been determined that the presence of hydrosulfoaluminate-type new formations in the hydration products and the presence of active mineral additives in its composition on the one hand, and on the other hand, the contact of cement stonewith the environment can cause the appearance of dangerous compounds (such as thaumasite) in hardening systems, the synthesis of which leads to the emergence of stresses in the structure of the material and its destruction. It has been established that as a result of the processes of isomorphic substitution, compounds of variable composition are formed, similar to solid solutions, due to which the strength of artificial stone is ensured in the later stages of hardening. On the other hand, the released sulfate ions can replace silicon groups in the tobermorite gel and form compounds similar to epistilbite (Ca6(Si(OH)6)3·(SO4)3·24H2O) (d=0.584; 0.399; 0.369; 0.354 nm). The strength indicators of artificial stone basedon modified fly ash cement binder compositions were investigated. It is associated with the directed formation of crystallochemically similar phases that can grow together, and the formation of artificial stone capable of structural and functional adaptation in various operating conditions will likely be due to the formation of solid solutions of hydrosulfoaluminocarbosilicate composition, hydrogarnet phases of the composition 3СаО·Al2O3·1,6SiO2·2,8H2O and modified calcium hydrosilicates of the epistilbite type Ca6(Si(OH)6)3·(SO4)3·24H2O) and scoutite (Са6Si6O18·2H2O·CaCO3). in the composition of new formations.