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Investigation of Corrosion Resistance of Composite Cements with a Complex Zeolite Modifier
Summary
Adding a natural mineral called zeolite to cement makes concrete significantly stronger and more resistant to damage from sulfates—harsh chemicals often found in soil and water that slowly break down conventional concrete over time. This matters because more durable concrete means longer-lasting infrastructure like dams, water treatment facilities, and pipes, which translates to safer water systems and fewer costly repairs or replacements for structures that protect public health.
Introduction. In the field of construction materials science, one of the priority research directions is the search for effective structure-forming additives to enhance the strength and density of hardened cement paste and concrete. Sedimentary zeolites represent a promising class of such materials. Their structure consists of a continuous framework containing cavities filled with mobile ions and water molecules capable of ion exchange and reversible dehydration. How-ever, insufficient attention has been paid to studying the resistance of zeolite-modified building materials to aggressive environments. The aim of this work is to develop a building material based on a cement-zeolite mixture that exhibits resistance to aggressive environments, particularly sulfate attack. Materials and methods. To achieve the stated objectives, cement compositions containing a zeolite component were developed. The zeolitic tuff was ground in a ceramic mill to a predominant particle size of 60 µm and incorporated at replacement levels of 5, 10, 20, and 30% by mass of cement. Additionally, a zeolite suspension (ZS) was prepared from fine-dispersed zeolite obtained using a jet mill (predominant particle size: 25 µm). The zeolite suspension with a concentration of 10 g/L was stabilized by two methods: ultrasonic treatment only; ultrasonic treatment combined with a polycarboxylate-based plasticizer added at 3 g/L. Corrosion resistance testing was conducted in a sulfate environment. Specimens measuring 4.0×4.0×16.0 cm were immersed in a 5% sodium sulfate solution for 30, 60, 90, and 180 days. Results. The results demonstrated that after 6 months of exposure to the aggressive environment, the compressive strength of the reference specimen (without additives) decreased by 7.8%. In contrast, when 5–10% of finely ground zeolitic tuff was incorporated in combination with the stabilized zeolite suspension, the compressive strength remained virtually constant throughout the specified curing period, both in water and in the sulfate solution. Compared to the control specimen, the strength of the modified specimens increased by 11–22% in water and by 22–29% in the aggressive environment. Furthermore, the chemical resistance coefficient for all modified specimens exceeded 0.8, confirming their sulfate resistance. Notably, the specimen containing 30% finely ground zeolite combined with the stabilized sus-pension exhibited a chemical resistance coefficient of 1.54. Conclusions. The chemical resistance coefficient for all modified specimens exceeded 0.8, confirming their sulfate resistance. Based on these results, the developed cement compositions incorporating a complex zeolite-based modifier show promising potential for application in the construction of hydraulic structures exposed to aggressive environ-ments.