Enhancement of shrinkage behavior of lightweight aggregate concretes by shrinkage reducing admixture and fiber reinforcement

This paper presents the results obtained from an experimental study conducted to investigate the effect of shrinkage reducing admixture (SRA) and steel fiber addition on the performance properties of lightweight aggregate concrete (LWAC). 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 amount of SRA used in the mixes was 0.75%, 1.5% and 3 % by weight of cement. Ring type specimens were used for the restrained shrinkage cracking test. At the same time, free shrinkage and weight loss of LWACs were measured. Moreover, the compressive and split tensile strength tests were undertaken. The results indicated that the use of steel fibers has little effect on compressive strength but it improves the split tensile strength. The addition of SRA decreases compressive strength without affecting 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.