Hydro-phobization of fine-grained portland cement concrete with spent filtering and bleaching powders

Abstract

The results of studying the chemical and phase composition of oil and fat production wastes - used filtering and bleaching powders are presented. It has been established that the crystalline phase of the powders is represented mainly by silicon dioxide, as well as aluminum, iron and titanium oxides, sodium and potassium aluminosilicates. The organic part of the spent filtering powders consists of waxes, while the bleaching powder phase contains fats and free fatty acids with unsaturated bonds. The concentration of water-soluble organic compounds in filtering powders does not exceed 30 mg/dm3, and in spent bleaching powder reaches 700–900 mg/dm3, which explains the decrease in surface tension at the solution-air interface in its presence and contributes to an increase in the effectiveness of its hydrophobic action in Portland cement systems. Analysis of the results of the study of the hardening process, strength, hydrophysical and corrosion properties of fine-grained Portland cement concretes confirmed the maximum effect of increasing the draft of the cone and mobility, due to the air entrainment of Portland cement mortars and their saturation with air microbubbles when bleaching powder is introduced. At the same time, in the presence of spent filtering powders, additional air entrainment, and, consequently, plasticization, is not observed. As a result of the formation of a protective layer in Portland cement concrete, there is difficulty in the access of water molecules to the solid phase, which leads to a significant improvement in hydrophysical properties. There is a decrease in water absorption by 45–54 %, salt absorption – by an average of 55 %, as a result, an increase in the coefficient of salt resistance of materials is recorded. The maximum effect of reducing salt corrosion and increasing the salt resistance coefficient of materials is due to the peculiarities of the capillary-porous structure of concrete in the presence of bleaching powder, the kinetics of diffusion of salt solutions in them, and the decrease in capillary suction and crystallization pressure of salts in the pores of the material.