MODIFIED COMPOSITE CEMENTS IN THE SYSTEM СаО–Al2O3–SO3–H2O

Abstract

Problem statement. One of the most important issues today is the reconstruction, reinforcement of buildings and structures, as well as the creation of new construction materials with the required physical and mechanical properties. The solution to this problem is possible through controlling and regulating the properties of the initial components of the concrete mixture, increasing the amount of surface components at the interface. To control the properties of construction materials, and thus to obtain the cement stone with the specified physical and mechanical properties is possible by means of using various mineral and surface-active additives in the composition of hardened cement stone. Development of sulfoaluminate compositions based on calcium sulfates, alumina cement and surface-active substances (surfactants) makes it possible to significantly expand the raw material base and the scope of application. The purpose of article – obtaining a composite binder with increased density, water resistance and improved technological factors. Conclusions. Alumina cement G-40, 50 and gypsum G-5-II in the ratio of 30−70 % (with hemihydrate gypsum being its main material) have been used in the research to achieve the set purpose. Their properties have been determined as well as the optimal ratio of components for obtaining a specific mineralogical composition with the maximum content of chemically bound water is carried out. Studies have shown that increased content of calcium sulfate has a positive effect on the amount of ettringite and that the optimal value is in the range of 30−40 % by weight of the composition. The exact ratio of components can be determined based on their mineralogical compositions and hydration process conditions. At the ratio of AC-40/G % – 70/30 % a considerable amount of calcium hydroaluminates remain; compressive and flexural strength is 14 and 10 MPa, respectively. When conducting research, the effect of plasticizers on the main technological and physical and mechanical properties of composite binders has been established: the Sika Viscocrete G additive has the greatest plasticizing effect. The composite binders presented above can be used for the manufacture of dangerous structures.