Mechanical properties of fibre reinforced concrete with recycled fibres

Abstract

Structural concrete members subjected to tensile stresses crack due to the brittleness of the concrete. Concrete brittleness can be reduced by adding various fibres to the concrete mix, whereby a composite material called fibre reinforced concrete (FRC) is created. This paper examines the effectiveness of recycled steel fibres (obtained from machining process discards) in increasing the ductility of concrete. Basic information on fibre reinforced concrete, including fibre types, the influence of a steel fibre addition on the mechanical properties of the material and the methodology of testing the main flexural properties of FRC according to different standards, is provided. The effect of a fibre addition was examined for three groups of test specimens differing in their fibres. A series made of plain concrete was prepared as the reference. In the other two groups the concrete matrix was reinforced with identical volume fractions of two types of steel fibres. Typical hook-end fibres were used in the first series while proposed recycled fibres were used in the second series. Fundamental mechanical properties such as: compressive strength, splitting tensile strength, flexural strength and equivalent flexural strength were tested on cube and beam specimens. Additionally, the distribution of strains in the middle cross section of the beams reinforced with the recycled steel fibres and subjected to bending was determined. The potential utilization of recycled steel fibres as a substitute for the fibres commonly used to reinforce concrete is investigated and discussed.