Optimising of Steel Fiber Reinforced Concrete Mix Design

Cementitious matrices are fragile materials that possess low tensile strength. The addition of fibres randomly distributed in these matrices, substantially improves their cracking strengths. However, the incorporation of fibres into plain concrete disrupts the granular skeleton and very quickly causes problems of mixing as a result of the loss of mixture workability that will be translated into a difficult concrete casting in site. This study was concerned on the one hand with optimising the fibres in reinforced concrete mixes in the fresh state, and on the other hand with assessing the mechanical behaviour of this mixture in the hardened state, in order to establish a compromise between the two states. An experimental study of an optimisation method of fibres in reinforced concrete while taking into account some parameters related to the matrix e.g. volume of admixture, volume of incorporated fibres and the volume of water and, cement as a function of workability time is presented. Finally, test specimens of the mixture optimised by this method have been tested in compression and bending. The proposed method is shown to result in fibre reinforced concrete of superior mechanical properties than fibre reinforced concrete optimised by Baron – Lesage method. Journal of Civil Engineering Research and Practice Vol.1(2) 2004: 67-7