Abstract
Bond strength between embedded bar and concrete plays vital role in the design of various reinforced concrete structural elements. Use of metallic and synthetic fibres has been shown to be an effective method to enhance tensile strength, reduce shrinkage and improve durability properties of concrete. However, making of synthetic fibres will not only deplete the natural hydrocarbon resources, but also add greenhouse pollutants to the environment. Hence, sisal fibre was considered as a potential alternative to polypropylene fibre. An experimental study was conducted to evaluate the influence of sisal fibres as mono-fibre and in combination with steel as hybrid fibre on bond strength of concrete. The performance of steel polypropylene fibre reinforced concrete (SPFRC) is compared with that of steel sisal fibre reinforced concrete (SSiFRC). Bond strength was conducted onM30 grade concrete for curing periods of 7, 28 and 90 days. Fibre dosages of 0.50%, 1.00%, 1.25% and 1.50% by volume of concrete were used. Results indicated that increase in steel fibre dosage improved the bond strength slightly. However, increase in fibre dosage of either PP fibres or sisal fibres resulted decrease in bond strength. Furthermore, sisal fibre reinforced concrete (SiFRC) showed inferior performance in bond strength as compared to polypropylene fibre reinforced concrete (PFRC). A detailed statistical analysis revealed that although no strong correlation between the compressive strength and the bond strength was evident from the experimental study, means of bond strength of both the hybrid groups did not differ significantly. In addition, empirical equations were proposed to predict the bond strength of fibre reinforced concrete (FRC) based on compressive strength.
Highlights
4.1 Bond Strength Effect of addition of steel and PP fibres separately and in combination on bond strength of fibre reinforced concrete (FRC) was evaluated for curing periods 7, 28 and 90 days
Presence of steel fibres was found to be beneficial to bond strength of concrete
Greater pull-out resistance of hooked-end steel fibres and increased grip between steel fibres and embedded bar could be the main reasons for enhanced bond strength of Steel fibre reinforced concrete (SFRC)
Summary
The bond between steel and concrete is critical in designing reinforced concrete structures. Bond forces along the bar are required to keep the steel and concrete deforming together. Forces that develop on the surface of bars to prevent significant slip from occurring at the concrete to steel interface are contributed to the bond. Role of steel fibres in enhancing the bond strength of FRC has been reported by various authors. Addition of Steel fibres was found to be effective in improving the bond strength of concrete when used them as mono fibres as well (Yazici and Arel, 2013). Steel fibre reinforced concrete (SFRC) exhibited higher resistance to pull-out load as compared to PFRC at the same fibre dosage. It was concluded that higher fibre length of steel fibres leads to higher bond strength
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