EXPRIMENTAL STUDY ON RESTRAINED SHRINKAGE OF SELF-COMPACTING CONCRETE BY RING TEST

The development of steel ring strain along with concrete ages and cracking behaviors of self-compacting concrete(SCC)induced by autogenous shrinkage alone and by drying & autogenous shrinkage are investigated through specimens sealed and circumferential drying by ring test, and compared with those of normal vibrated concrete (NC). The mix proportion parameters of SCC include its fly ash content, fly ash and slag content, and water to binder ratio. Steel ring strains and cracking ages of specimens sealed and circumferential drying are discussed, ‘the standardized steel ring strain’ and ‘the nominal cracking age’ have been proposed as two concrete cracking indexes in the ring test. The results also showed that the given factors of mix design have different even opposite effects on restrained drying shrinkage and restrained autogenous shrinkage. Thusly, it is necessary to study the two kinds of shrinkage separately. The changes of both ‘action’ and ‘resistance’ in concrete cracking can be integrated by the cracking index proposed, and thus the overall performance of concrete cracking can be evaluated.