COMPOSITION AND DURABILITY OF FIVE YEAR OLD GASIFIER SLAG-CEMENT CONCRETES

Concrete cubes, made from three different Portland cements and several cement-gasifier slag blends, have been stored in air, tap water, soft acid water, sulphate solutions, and in spray, tidal and full immersion marine zones for periods of up to five years to assess their durability. Compressive strength data are presented and selected specimens have been examined by X-ray diffraction to identify the phases present. Electron probe microanalysis of a concrete based on a blended cement containing 60% ordinary Portland cement and 40% gasifier slag, which had been stored in the tidal zone of the marine environment, is compared with that of a blended cement paste after storage in tap water. The relationship between the Si:Ca and Al:Ca ratios of the calcium silicate hydrate formed, the formation of stratlingite and the Mg:Ca ratio of the slag hydrate are discussed. The concretes are based on blended cements incorporating 60% replacement of cement by gasifier slag have good durability especially in the more aggressive environments, although these concretes are susceptible to carbonation if not cured properly. (A) For the covering abstract of the conference see IRRD 853281.