EFFECTS OF ACID CORROSION WITH FORMATION OF SOLUBLE PRODUCTS ON A CEMENT TYPE CEM I

摘要

Understanding the effects of various aggressive mediums on the cement stone offers an opportunity to arrest the aggressive action. The acid corrosion occurs below the pH of 6.5, and may originate from: (ⅰ) acid rains, increasingly frequent over the last decades and caused by SO_2 and NO_x emissions leading to formation of H_2SO_4 and HNO_3; and (ⅱ) the life and service of industrial structures in acid-generating mediums. The paper aimed at investigating the effect of 4 inorganic and organic acids (HCl, HNO_3, HOOCH, and CH_3COOH) in 3 different concentrations on a cement type CEM I. The cement samples—pasts and mortars—were kept in water for 28 days and then in acid solutions for 270 days. Determination of strength and mass loss were carried out on cement mortars at terms of 28, 90, 180, and 270 days. The compressive strength underwent decreases, more such for the samples kept in organic acid solutions. The cement pastes underwent chemical analysis and XRD analysis at terms of 28, 90, 180, and 270 days. Significant decreases of CaO concentration with corresponding increasing of the remainder of oxides have been revealed by chemical analysis on the corrosion products. In addition, an increase in acid concentration has led to an increase in the thickness of the layer of corrosion products.