Acid attack calcium aluminate cements

Calcium aluminate cements are extremely highly resistant to various aggressive media. They were invented as a result of concrete searching, resistant to sulphate solutions attack. Besides the sulphates, they are resistant also in the acidic waters enviromnent (see Chap. 6) as well as in sea water. This was proved by examination of calcium aluminate cement concretes after many years of exploitation in different conditions. For example Lea [5] reports that the concrete samples, moreover those with anhydrite aggregate, stored many years in gypsum water, do not show any symptoms of destructiom The other concrete samples were successfiilly stored for 20 years in Medicine Lake in Dakota, where the concentration of sulphates was... 

The calcium aluminate cement concrete is resistant to the attack of weak solutions of mineral adds too. The resistance to otganic acids is limited to the pH value of about 4. However, the porous calcium aluminate cement concrete is not stable in the soft water, if permeable. 

Mortar Deterioration. Mortar may decay from the formation of calcium sulfoaluminate (which causes expansion and loss of mortar strength) and by the attack of pollutants in the atmosphere. Portland cement contains tricalcium aluminate, which reacts with sulfates in solution to form calcium sulfoaluminate. Exhaust gases from automobiles contain sulfur dioxide, sulfur trioxide, and nitrous oxides. These oxides react with moisture in the atmosphere to form sulfurous acid, sulfuric acid, and nitric acid, which are the attacking agents. As attack continues over the years, the mortar joints may crack, the surface of the joint may spall off, and the mortar may become softer and more crumbly. 

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