Action of Natural Alkali Waters on Portland Cement

Of the salts common to alkali bearing waters those of magnesium are the most active on cement. Magnesium sulphate solution in intimate contact with cement reacts very rapidly with practically all the calcium of the latter producing calcium sulphate and an insoluble compound of magnesium. The reaction results in a material increase in the weight and volume of the cement. Magnesium chloride rapidly reacts with cement replacing practically all the calcium by magnesium. Chemically equivalent amounts of calcium and magnesium are involved in the exchange. Slight decreases in the weight and volume of the cement accompany this reaction. The salts of sodium are less active than the corresponding ones of magnesium