Internal relative humidity and drying shrinkage of hardening concrete containing lightweight and normal-weight coarse aggregates: A comparative experimental study and modeling

- The IRH and drying shrinkage of lightweight and normal-weight concrete are measured.
- The internal curing effect of lightweight aggregates reduces IRH drop in concrete.
- Drying shrinkage should be evaluated in terms of average IRH drop.
- A model of the shrinkage coefficient is proposed.
- Ultimate shrinkage is inversely proportional to the compressive strength of concrete.

The effect of lightweight and normal-weight coarse aggregates on the internal relative humidity (IRH) and drying shrinkage of hardening concrete was investigated experimentally. The compressive strength, elastic modulus, IRH, and drying shrinkage of concrete specimens were measured. Lightweight and normal-weight concretes exhibited different variations in IRH and drying shrinkage. The results suggest that drying shrinkage should be evaluated in terms of average IRH drop at equivalent age, considering the development of elastic modulus for lightweight and normal-weight hardening concretes. The model of the shrinkage coefficient can be useful for evaluating the drying shrinkage of lightweight and normal-weight hardening concretes.