Study on early autogenous shrinkage and crack resistance of fly ash high-strength lightweight aggregate concrete

A self-designed test and the elliptical ring test were applied to test the early autogenous shrinkage and crack resistance of fly ash high-strength lightweight aggregate concrete in which 10-30% of cement was replaced by equivalent amounts of fly ash of different fineness. Test data of reference lightweight aggregate concrete were provided. The results showed that (a) the early autogenous shrinkage of concrete was restrained in fly ash high-strength lightweight aggregate concrete, and further analysis indicated higher fly ash content and higher fly ash fineness resulted in less autogenous shrinkage; (b) in a lower water-binder ratio, early autogenous shrinkage increased significantly as the water-binder ratio decreased, and, moreover, pre-wetting of lightweight aggregate had a great effect on controlling early autogenous shrinkage; (c) the elliptical ring test results indicated that the addition of fly ash significantly improved crack resistance of lightweight aggregate concrete and that this improvement becomes obvious with increasing fineness of fly ash. Therefore, in practice, the addition of fly ash could be a technical alternative to reduce early autogenous shrinkage and to enhance the crack resistance of lightweight aggregate concrete.