Importance of drying to control internal curing effects on UHPC
Experiments showed that the self-desiccation of ultra-high performance concrete (UHPC) cannot be prevented by external curing, such as water curing, but can be prevented by internal curing. Although the desiccation and resulting shrinkage of UHPC were effectively mitigated by the internal curing, a slow strength development was found when maintaining a high internal relative humidity.
Under water-curing conditions, the internally cured UHPCs showed 12–17% lower strength at 28 days compared with the reference sample. However, the results were 0–1% when exposed to dry air (relative humidity: 60%) between 7 and 28 days, showing accelerated external drying. The results show that the early-age shrinkage-related problem of UHPC can be fundamentally resolved, without a negative effect on strength, by controlling the drying period.
The study is published in: Cement and Concrete Research Volume 108, June 2018, Pages 20-30.