Performance of fly ash incorporated recycled aggregates concrete column under axial compression: Experimental and numerical study

Abstract

The reinforcing steel properties and concrete constituents such as binder materials as well as type and geometry of coarse aggregates influence performance of a reinforced concrete column under uniaxial compression. This paper investigates full-scale reinforced concrete (RC) column specimens comprising 100% recycled coarse aggregates and fly ash as partial replacement of cement. Two cement replacement ratios such as 20% (FA20RAC) and 30% (FA30RAC) are considered. Particle packing method is used for proportioning of concrete. This mix design method leads to dense packing with minimized voids in fly ash incorporated recycled aggregate concrete (FARAC) mix requiring less fresh binder content. As compared to natural aggregate concrete (NAC), the load carrying capacity of FA20RAC and FA30RAC column specimens are higher by about 4% and 9% respectively. Prediction of full-scale column behaviour from the standard cylinder test highlights size effect that affects the peak load less in FARAC as compared to NAC. Two-dimensional numerical analysis of a transverse tie confined concrete is carried out using fibre element method. The effect of core concrete on the development of confining pressure is examined for RC columns with similar arrangement and properties of lateral ties.