Effect of silica fume and steel fiber on the mechanical properties of the concretes produced with cold bonded fly ash aggregates

This paper reports an experimental study on the mechanical properties of steel fiber incorporated plain and silica fume (SF) concretes produced with cold bonded artificial fly ash aggregates (AFAs). Two concrete series with water-to-binder (w/b) ratios of 0.35 and 0.55 were designed. SF incorporation was achieved by 10% replacement of the weight of cement by silica fume. Two types of hooked-end steel fibers with length/aspect ratios of 60/80 and 30/40 were utilized. AFA, produced from cold bonding pelletization of 90% class F fly ash and 10% Portland cement, was used as coarse aggregate in all of the concrete mixtures. The mechanical properties investigated were compressive strength, modulus of rupture, and bonding strength between rebar and concrete. The tests were carried out at the end of 28 day water curing. Analyses of variance of the experimental results were performed and the contributions of the significant factors on the mechanical characteristics of the concretes were determined for statistical evaluations. Moreover, correlation of the experimental data was carried out to monitor the interaction between mechanical properties and bonding strength of the concretes. The results demonstrated that incorporation of SF and utilization of different types of steel fiber reinforcements significantly affected the mechanical properties of the concretes regardless the w/b ratio.