Flexural responses of hybrid steel–polyethylene fiber reinforced cement containing fly ash.pdf

C/locate/conbuildmat Construction and Building Materials 21 (2007) 1088–1097 and Building MATERIALSFlexural responses of hybrid steel–polyethylene fiber reinforced cement composites containing high volume fly ash Shaikh Faiz Uddin Ahmed a,*, Mohamed Maalej b, P. Paramasivam b a Graduate School of Engineering, Tohoku University, Sendai, Aoba-Ku 980-8579, Japan b Department of Civil Engineering, National University of Singapore, Blk E1A #07-03, 1 Engineering Drive 2, Singapore 117576, Singapore Received 2 December 2005; received in revised form 28 December 2005; accepted 23 January 2006 Available online 20 March 2006Abstract Strain hardening and multiple cracking behavior of hybrid fiber reinforced cement composites containing different hybrid combina- tions of steel and polyethylene (PE) fibers under four-point bending are reported. The total volume fraction of fibers was kept constant at 2.5% to maintain a workable mix. Effects of increase in fly ash content as partial replacement of cement beyond 50%, such as 60% and 70% on the flexural response of hybrid steel–PVA (polyvinyl alcohol) and steel–PE fiber composites are also evaluated here. Among com- posites with different volume ratios of steel and PE fibers, the composite with 1.0% steel and 1.5% PE was found to show the highest flexural strength and that with 0.5% steel and 2.0% PE exhibited highest deflection and highest flexural toughness. Generally, the steel–PE hybrid composites exhibited lower flexural strength but higher deflection capacity than steel–PVA hybrid composites. The rate of strength loss after peak load in steel–PE hybrid composites was found low compared to steel–PVA hybrid system. The 50% replace- ment of cement by fly ash is found to be an optimum fly ash content in hybrid fiber composites.  2006 Elsevier Ltd. All rights reserved. Keywords: Hybrid fiber; Strain hardening; Multiple cracking; Toughness; Fly ash1. Introduction High performance fiber reinforced cementitious compos- ites (FRCC)_e