Self-Cured Self-Consolidating Concrete

At the beginning of 21st century a concrete mix was introduced to the construction industry which, based on its mix proportion design, can be self-compacted and self-cured. Its performance is very promising and must be studied carefully. In this research the effect of internal curing, using saturated lightweight aggregate (Leca), on autogenous shrinkage of high strength self-consolidating concrete with water to cementitious material ratio of 0.3 was investigated. Two amounts of 30 and 40 percent by volume replacement of fine and medium size aggregate were considered. After testing the fresh properties of each mixture, early age autogenous shrinkage was measured using a laser beam, starting immediately after casting and was recorded automatically at 10 minutes intervals. Compressive strength, autogenous and drying shrinkage of hardened concrete was also studied. The results indicate that the autogenous shrinkage of control mix is considerable and the major portion of it, occurs in the first 24 hours after casting. With 30% replacement of normal sand with saturated Leca of same size, this early age shrinkage decreased and did not increase much in the first week. For the medium size aggregates, the amount of replacement should be increased in order to avoid shrinkage. The drying shrinkage of control mix and mixtures with 30% aggregate replacement were similar. The 28 days compressive strength of mixture with 30% medium size LWA was reduced by 13%. Using smaller size LWA or increasing the amount of replacement lead to more reduction of the compressive strength. To reduce this negative effect stronger aggregate with sufficient absorption capacity is recommended.