The composition and structure of sand lime concrete as a factor of corrosion resistance with exposed to sodium chloride. Part 1. Structure at the macro- and micro-scale level as a permeability factor

The article is devoted to the study of the structure of lime sand concrete based on a lime-silica binder, depending on the initial activity of the raw material mixture and its effect on the kinetics of absorption of chlorine ions under the influence of alternating wetting and drying in a solution of sodium chloride. Lime sand concrete samples were made from mixtures of quartz sand and lime-silica binder, the CaO activity of the mixtures ranged from 7.5 to 11.5%, in increments of 2%. Autoclave treatment of the samples was carried out in an industrial autoclave at a pressure of 0.9 MPa with exposure for 8 hours. It is shown that the structure of lime sand concrete at the macro level consists of a continuous matrix of crystalline formations and discretely distributed sand particles and gaseous inclusions in the form of pores with a diameter of 10-(4–5) m, which are significantly larger in the composition with an activity of 7.5% of the raw material mixture. At the micro level, the structure is represented by individual consolidated morphological differences consisting of calcium hydrosilicates: tobermorite and α-C2S hydrate, as well as elements of their fusion and intergrowth, which are permeated by micropores with a radius of 10-(6–7) m.