Effect of pozzolanic material on the restrained shrinkage behavior of self-consolidating concrete

Self-consolidating concrete (SCC) has been the subject of various research projects, and its use has been a source of increasing interest in industry. The very early phase of SCC research mainly focused on mechanical and fresh concrete properties. The area of SCC research was then enlarged with the inclusion of shrinkage behavior. This was necessary because SCC as a concrete type was always presumed to exhibit higher levels of free and restrained shrinkage due to its higher cementitious material content. Given that concrete in general has very low tensile strength capacity, especially the deformations caused by restrained shrinkage behavior are among the primary concerns related to SCC. Restrained shrinkage behavior of SCC is investigated in this study, with the emphasis on cracking ages and patterns. The AASHTO-T334 test setup is used to evaluate the cracking potential of the SCC mixes. In addition to the steel ring data collection method of AASHTO-T334, Vibrating Wire Sensor Gages (VWSG) were also implemented to collect concrete strain measurements. Many other laboratory tests such as the compressive strength, splitting tensile strength, modulus of elasticity, and free shrinkage were performed in companion with the restrained shrinkage test. The resistance to restrained shrinkage cracking of the SCC was found to be weak since all the SCC mixes cracked under restrained shrinkage before day 56 after casting. Moreover, except for one SCC mix, the cracking was observed only between day 19 and 31 after casting. Amount of total cementitious material was found to have the greatest effect on the restrained and free shrinkage performance of the SCC mixes. Partial replacement of Portland cement with high percentages of fly ash was found to have the potential to increase the elapsed time until cracking. If silica fume was used as a replacement, the cracking performance was slightly worse whereas the free shrinkage strain increased 10 % at day 56 after casting.M.S.Includes abstractIncludes bibliographical referencesby Ufuk Ate