Environment friendly concretes

An optimal amount of slag minimises concrete cost and carbon dioxide emissions

Cement suppliers produce CEM II grades with varying amounts of slags. However, the optimal amount of slag will depend on various constraints and requirements of the concrete plant. Another issue is that as long as carbon dioxide emissions do not have a significant cost, the cost optimal recipe will not likely be the optimal from the point of view of carbon dioxide emissions. Consolis wants to introduce more and more environment friendly concretes in its products, and it is important to determine recipes that serve the purpose well, instead of just using cements containing slags. An experimental investigation was carried out in the last few months to mathematically determine optimal recipes for minimal cost and for minimal carbon dioxide emissions. A total of 21 experiments with different recipes were carried out, from which nonlinear models were developed for early strength, 28 day strength and workability, besides simple equations for paste volume, carbon dioxide emissions and cost. This article describes the experimental data, development of nonlinear models and calculations of optimal recipes.