Abstract
Durability of reinforced concrete is one of the main demands in civil engineering.Operating conditions, particularly in aggressive mediums, determine durability of constructions.Sulfate mediums are among the most aggressive ones which cause steel reinforcement corrosion. Themodern requirements for high consistency fresh concretes are governed by practice. This way thedisturbance of reinforcement passive state can be caused by changes in hardened concrete especiallyin aggressive mediums. Thus, the restriction of SO42- ions transport in concretes, which are obtainedfrom high consistency fresh mixes and exploited in sulfate mediums, can be considered as an actualproblem.The paper is devoted to protection of concrete surface by coating based on alkali-activatedaluminosilicate binder from SO42- ions transport to prevent steel reinforcement corrosion. It wasshown that the coating with thickness of 3 mm ensures total concrete protection. It was revealed thatpermeability of concrete depending on cation decreases in the row (NH4)2SO4>Na2SO4>MgSO4. Theprotective function of coating was simulated by application of mentioned salts as admixtures. LesspH values of water extracts of the binder during hydration while using of 2.5 % MgSO4 is evidenceof advanced crystallinity of zeolite-like sulfate-containing hydroaluminosilicates with participationof Mg2+ ions equal to Са2+ ions. While content of (NH4)2SO4 was increased up to 5.0 % less pH wasfixed due to decelerated formation of zeolite-like minerals. Stability of pH values in presence ofNa2SO4 (0.5…2.5 %) was caused by no influence on structure formation. Thus, the restriction of SO 2-ions transport in protective coating is due to their binding by alkaline aluminosilicate binder inzeolite-like minerals with higher crystallinity due to presence of Na+, NH + and Mg2+ cations fromsulfates.
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