Role of Alumina, Magnesia and Manganese Oxides on the Hydration and Hardening of Slag Glasses

Abstract

The effect of increasing amounts of each of Al203, MgO and MnO in synthetic slag glasses corresponding to Indian slag compositions, on their hydraulic behaviour after activation with cement clinker has been studied. Results showed lowering of strength of cements at all ages with increase in Al2O3 content in glasses beyond 22 percent in spite of the progressive increase in chemically combined water. Presence of MgO up to 2.5 percent improved the strength but a higher content was found to be detrimental. High MgO in glass did not cause unsoundness in cement. MnO up to 2.5 percent was beneficial but a higher content affected the early strength adversely.The hydration products identified were mainly calcium silicate hydrate and tetracalcium aluminate hydrate. Magnesium or manganese containing hydration products could not be identified. These ions appear to go into solid solution in the hydration phases. The study explained the pattern of strength development in Indian granulated slags.