Dehydration factor upon activation of building sand by ultraviolet radiation

Abstract

The analysis of the influence of ultraviolet irradiation of building sand, which is a filler in a concrete mixture, on the dependence of the strength of concrete on the content of the filler. With an increase in the sand content due to the hydrophilicity of the surface of its particles in the mixture, the amount of free water necessary for hydration of the cement and the formation of cement stone decreases. Along with a decrease in the content of binder cement, this factor is an additional reason for the decrease in concrete strength with increasing sand content. Ultraviolet irradiation leads to dehydration of the surface of sand particles and the appearance of hydrophobic centers. With the increase in the hydrophobicity of sand in the concrete mixture, the content of free water available for cement hydration increases, and the strength of the cement stone increases. The change in the hydrophobicity of the surface of sand particles depending on the irradiation time is nonmonotonic. Therefore, there is an optimal ultraviolet activation mode that provides the greatest increase in concrete strength.