Effect of mineral admixtures on shrinkage measured on massive concrete elements

Volumetric change of concrete produced as hydration progresses and measured on massive concrete blocks is totally different from that of small samples. The temperature rise in the last case is low and can be neglected. However, for massive concrete elements, hydration heat is very high and induces large thermal strains. At early age, the combination of these two types of strains (self-desiccation and thermal) must be taken into account to prevent any risk of early-age cracking. This study highlights the effect of four different types of mineral admixtures on the development of shrinkage measured on massive concrete elements that perfectly simulate real concrete structures. Concrete mixtures with three W/B, 0.26, 0.30 and 0.35, and four types of binders were used. Experimental results have shown that the use of fly ash in combination with a small amount of silica fume reduces shrinkage and hydration heat. Also, shrinkage is intimately related to the mineral admixtures used. This is illustrated by the difference between the effect of silica fume and metakaolin on shrinkage.