Abstract
The article shows that one of the ways to increase the sulfate resistance of cements is to use as an additive of pozzolanic action based on highly dispersed zeolite, which increases the corrosion resistance of concrete. Physical-chemical properties of zeolite tuff as a mineral constituent of Portland cements with the addition of pozzolana are presented. The use of modern grinding technology by separate grinding of Portland cement clinker and natural zeolite in mills with separators of the latest generation allows to obtain high quality Portland cement with zeolite CEM II/A-P 42.5 R PJSC "Ivano-Frankivsk Cement", characterized by high early strength. It is shown that the replacement of the clinker component with zeolite leads to a decrease the content of clinker minerals C3S and C3A in cements, which significantly limit the corrosion resistance of cement stone. Highly dispersed zeolite is characterized by increased pozzolanic activity (after 28 days, the absorption of Ca(OH)2 is 200-250 mg/g). Due to pozzolanic reaction with the formation of C-S-H-phases, the content of calcium hydroxide in the paste based on CEM II/A-P 42.5 R is reduced by 2 times compared to Portland cement CEM I 42.5 R. Decrease in the concentration of Ca(OH)2 in cement pastes eliminates the possibility of the formation of a significant amount of ettringite, which causes sulfate corrosion of cement stone. It was found that during the hardening of Portland cement CEM II/A-P 42.5 R under the influence of sulfate and magnesium media, the coefficient of corrosion resistance Ks after 56 days is 1.16 and 0.98, respectively, while for samples based on Portland cement CEM I 42.5 R Ks decreases by 1.2-1.3 times. The results of researches of influence of aggressive environments on corrosion resistance of Portland cement with the increased content of zeolite type CEM ІІ/В-Р 42.5 are resulted. For Portland cement CEM ІІ/В-Р 42.5 the coefficient of corrosion resistance in the conditions of sulphate environment Кс90 = 1.47. Portland cements with zeolite strength class 42.5, modified with superplasticizers of polycarboxylate type, are characterized by high sulfate resistance and should be used for the manufacture of concrete classes C25/30...C50/60 for construction of dams, hydraulic structures, sewers storage of waste from livestock farms, etc. Modified rapid-hardening Portland cements with the zeolite additive provide technical, environmental and economic effects in the manufacture of concrete and reinforced concretes of hydraulic structures.
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