STEEL-CONCRETE BOND STRENGTH OF SELF- COMPACTING CONCRETES PARTIALLY INCLUDING ARTIFICIAL FLY ASH AGGREGATES

The objective of this experimental study is to investigate the adherence between reinforcing steel bar and self-compacting concretes in which normal aggregate was replaced with lightweight aggregate in terms of bond strength with pull out test method. Lightweight aggregates were produced by cold bonding pelletization of 90% fly ash and 10% Portland cement by weight in a tilted revolving pan at an ambient temperature. The self-compacting lightweight concretes were produced with constant binder content of 550 kg/m3 and at a water-to-binder ratio of 0.32. 20% of Portland cement was replaced with fly ash by weight. In the mix design, the total aggregate volume was designated as 50% fine and 50% coarse aggregates by volume. Three different self-compacting lightweight concrete series were designed in this study. In the first series, the natural fine aggregate was replaced with the lightweight fine aggregate at the contents of 0, 20, 40, 60, 80, and 100% while in the second series, the natural coarse aggregate was substituted with the lightweight coarse aggregate at the same contents with first series. The third self-compacting concrete series was the combination of the first and second series, namely both natural fine and coarse aggregates were replaced with the lightweight fine and coarse aggregates at the replacement levels of first and second series. Totally 17 self-compacting concrete mixtures were designed and produced. The compressive, splitting tensile and bond strength of the concretes were investigated at the age 28 days. The experimental results indicated that increasing the lightweight aggregate content resulted in systematical decreasing in the aforementioned properties. In addition to experimental investigation on the effect of lightweight aggregate utilization on such properties of concretes, the influence of the lightweight aggregate replacement level and its type was statistically evaluated by using two-way analysis of variance (ANOVA) technique. The statistical evaluation revealed that both aggregate content and its type had remarkable effect on such properties of the self-compacting lightweight concrete.