Shrinkage of self-compacting concrete made with blast furnace slag as fine aggregate

• Replacing sand by slag gives rise to mixtures with higher total pore volume.
• At early ages SCCs with slag show similar strength, but in the long term it increases.
• SCCs with slag show a higher autogenous shrinkage.
• Due to their higher porosity, SCCs with slag are less stiff and lose water faster.
• SCCs containing slag show higher total shrinkage.

The aim of this experimental work was to study shrinkage evolution with age in self-compacting concretes (SCC) in which part of the fine aggregate was replaced by granulated blast furnace slag (GBFS) as sand. Seven types of SCC were made with a w/c ratio of 0.55 and different slag contents. The results show that replacing sand by GBFS gives rise to mixes with higher pore volume but with slightly finer porous structure (smaller median pore and threshold diameters). At early ages slag SCCs have similar compressive strength to that of the reference concrete, although in the long term their strength increases as a result of slag reactivity. We also observed that the higher the slag content, the higher were both autogenous and drying shrinkage and consequently also total shrinkage. In comparison with the reference concrete, the increase in total shrinkage was found to be of the order of 4% and 44% when 10% and 60%, respectively, of the sand was replaced by slag.