Influence of Different Secondary Raw Materials on the Granulated Blast-Furnace Slag Reaction

For the practical use of granulated blast-furnace slag as a clinker substitute, the addition of an activator is necessary, in order to ensure that a sufficient early and ultimate strength will be reached. Up to now, portland cement has been the most common type of activator for granulated blast-furnace slag. The addition of portland cement leads to the activation of the granulated blast-furnace slag either on an alkaline or, to a minor extent, on a sulfate basis. Materials which prevent the obstruction of the latent hydraulic reaction by a close gel layer of reaction products work as an activator. In this paper, the influence of different fine-grained additives, e.g. fly ash or cement kiln dust, on the granulated blast-furnace slag reaction and the strength development is discussed. The investigations showed that it is basically possible to manufacture composite cement with a high content of granulated blast-furnace slag by using industrial by-products. These cements show particularly a higher early strength than the reference cement, dependent on the composition respectively to the addition. The reactivity of the blast-furnace slag is strongly influenced by the chemical composition of the addition or activator but also by the mineralogical and chemical composition of the blast-furnace slag.