The influence of bleeding, extra water and superplasticizer on the SCC plastic shrinkage cracking: case of hot weather

摘要

Self-compacting concrete (SCC) is a new material able to be put in place without vibration. However, this advantage is offset by some drawbacks, such as plastic shrinkage, one of the causes of cracking in concrete. Furthermore, the presence of fines absorbs a large amount of water and therefore minimizes bleeding. This paper endeavours to provide a better understanding of the appearance of plastic shrinkage cracking, and to justify his relation with bleeding phenomena. Five SCC formulas with different W/C ratios were prepared and compared to the same range of ordinary concrete (OC) in terms of restrained shrinkage (cracking width). At the same time, a study of cracks' propagation over time (cracking length) was conducted on the equivalent mortars (mOCe, mSCCe). Mixtures were placed in different hot environmental conditions. The results showed that bleeding significantly reduces cracking length and has no effect on cracking width. In the second part, extra water and superplasticizer was proposed as a solution to prevent SCC cracking and findings show the addition of 10% of water reduces cracking length and a slightly lower addition of superplasticizer reduces SCC's crack width.