Use of shrinkage reducing admixture and steel fiber to control shrinkage cracking of lightweight concretes

ABSTRACTUSE OF SHRINKAGE REDUCING ADMIXTURE AND STEEL FIBER TO CONTROL SHRINKAGE CRACKING OF LIGHTWEIGHT CONCRETESMOHAMADAMEEN, AlaaM.Sc. in Civil EngineeringSupervisor: Associated. Prof. Dr. ERHAN GÜNEYİSİJuly 2012, 91 PagesThis thesis presents the results obtained from an experimental study conducted to investigate the effect of shrinkage reducing admixture (SRA) and steel fiber addition on some of the properties of lightweight aggregate concrete (LWAC). A total of seven LWAC mixes with SRA or steel fibers were produced at the same water-cement ratio using cold-bonded fly ash coarse aggregates. The percentage of steel fiber volume fractions used in the mixes was 0.25, 0.75 and 1.25. The amounts of SRA used in the mixes were 0.75%, 1.5 % and 3 % by weight of cement. Ring type specimens were used for the restrained shrinkage cracking test. Free shrinkage weight loss, compressive and split tensile strength tests were also undertaken. The results demostrated that the use of steel fibers has little effect on compressive strength but it enhances the split tensile strength. The addition of SRA diminishes compressive strength without influencing tensile strength. Moreover, the utilization of steel fiber or SRA extends the cracking time and reduces the crack width of LWAC resulting in finer cracks associated with lower free shrinkage.Keywords:Lightweight concrete, Mechanical properties, Shrinkage cracking, Shrinkage reducing admixture, Steel fiber.