Building and Construction Engineering Department, University of Technology, Baghdad, Iraq.


A knowledge of the concrete vibration after casting have led to improve the mechanical properties of concrete, reduce the deformations due to creep and shrinkage and reduce the concrete permeability. At the Structural and Material Laboratories- Building and Construction Engineering Department, University of Technology, series experimental tests on prisms, cubes and cylinders were carried out to investigate the effect of waiting time after initial vibration on the flexural-tensile strength, compressive strength and splitting tensile strength of fiber reinforced concrete. The variables considered in this study were; the amount of steel fiber and waiting time after initial vibration. The test results showed that the concrete prisms without steel fiber show approximately linear behavior till the maximum flexural-tensile load due to brittle behavior of concrete. The maximum improvement in flexural-tensile strength of concrete prism occurs after the initial setting of concrete i.e after 90 minutes of waiting time. The re-vibration after time period increase the stiffness of concrete prism in case of presence of steel fiber compared with the prisms initially vibrated only. The modulus of rupture of concrete prism increased with the increasing of steel fiber content for all waiting time before re-vibration.


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