Shrinkage and Crack Propagation of Flowing Concrete at Early Ages

Flowing concrete is a highly flowable and segregation resistant concrete. Shrinkage of the concrete at early ages up to 24 hours under a constant air flow of 8 m/s starting at the age of 2 hours, and crack propagation of the concrete in a restricted form with a thickness of 50 mm have been studied. The experiments were done by controlling the following four mixture parameters: (1) Water-cement ratio: 0.60, 0.45, 0.35, 0.30 and 0.27; (2) Unit amount of water: 185, 175 and 170 kg/cu m; (3) Type of cement: normal, high early strength and belite portland cement; and (4) Type of inorganic admixture: a ground granulated blast furnace slag and a fly ash and their respective mixture proportions. Effects of the above parameters on crack propagation at early ages were investigated on the basis of the authors' crack evaluation criteria.