Curing Duration Optimization to Reduce Shrinkage Cracking in One-Part Alkali-Activated Slag Concrete

The consequences of inadequate curing on one-part alkali-activated slag concrete (O-AAS) performance relative to ordinary Portland cement concrete (OPCC) have been investigated in this research. Prior to exposure to unsaturated conditions, samples underwent initial moist curing for durations ranging from 24 hours to one year. The testing program included compressive strength evaluation, chloride ion transport analysis, and measurement of free and restrained shrinkage. In addition, cylindrical cores were extracted from concrete columns to assess internal strength and chloride penetration resistance. Under unsaturated exposure, O-AAS exhibited a strength-aging phenomenon, with up to a 37% decrease in compressive strength over 360 days, whereas OPCC maintained stable strength. Reduced curing durations at ambient temperature resulted in lower compressive strength and increased chloride migration coefficients. With adequate curing, long-term performance was comparable to that under continuous saturated conditions. Extending initial curing from 24 hours to one week decreased 28-day free shrinkage by 18.1% and restrained crack width by 56.0%. Core analysis revealed that inadequate curing led to microcrack development in O-AAS, while sufficient curing duration resulted in performance matching that of continuously saturated specimens. For OPCC, core performance did not differ significantly in varying curing regimes. Early-age curing is critical for mitigating shrinkage damage and preserving long-term durability in O-AAS concretes, especially under unsaturated environmental conditions.