Contribution of steel fiber and metakaolin in enhancing mechanical behavior of high strength concretes

This study reports the results of an experimental study on mechanical properties of plain and metakaolin (MK) concretes with and without steel fiber. To develop the metakaolin included concrete mixtures, Portland cement was partially replaced with MK as 10% by weight of the total binder content. Two types of hook ended steel fibers with length/aspect ratios of 60/80 and 30/40 were used to produce fiber reinforced concretes. Two series of concrete groups were designed with water to binder ratios (w/b) of 0.35 and 0.50. The combined effects of MK and different types of steel reinforcement on the compressive, flexural, splitting, and bonding strength of the concretes were investigated. All tests were conducted at the end of 28 days of curing period. Analyses of variance on the experimental results were carried out and the levels of the significance of the variables on the mechanical characteristics of the concretes were determined. Correlation between the measured parameters was also carried out to better understand the interaction between mechanical properties of the concretes. Moreover, the microstructure of plain and steel fiber reinforced concretes incorporated with MK was observed by scanning electron microscopy (SEM). The results indicated that incorporation of MK and use of different types of steel fibers significantly affected the mechanical behavior of the concretes, irrespective of w/b ratio.Keywords: Bonding strength; Compressive strength concrete; Metakaolin; Steel fiber; Tensile strength