Use of recycled aggregates as internal curing agent for alkali-activated slag system

This study aims to investigate the feasibility of recycled aggregates (RA) as an internal curing agent for an alkali activated slag (AAS) system. The physical and chemical characteristics of the aggregates were studied through various analytical techniques including X-ray diffraction, thermogravimetry, mercury intrusion porosimetry, and indirect alkalinity measurements. The compressive strength, degree of hydration, and autogenous and dry shrinkages of AAS generated with RA were measured and compared with those of AAS made using artificial lightweight aggregates. The use of RA can reduce the autogenous shrinkage of an AAS system without a decrease in compressive strength. The degree of hydration for AAS mortar was not increased by the addition of RA owing to the dilution effect of the alkali activator, which was caused by the additional water supplied from internal curing materials.