Fire Properties Of Green High Performance Fiber Reinforced Cementitious Composites Frame Beams

Green High Performance Fiber Reinforced Cementitious Composite(GHPFRCC)materials have excellent direct tensile and flexural performance at normal temperature,and GHPFRCC frame beams have outstanding ductility and shear resistance.However,there lacks of researches on the toughness and fire resistance of GHPFRCC frame beams.This study first investigates the direct tensile and flexural performance of GHPFRCC at the material level,and the fire resistance of GHPFRCC frame beam at the component level.The work and conclusions are briefly summarized as follows:(1)Uniaxial tensile tests of GHPFRCC specimens were conducted after exposure to high temperatures(200 ?,400 ?,600 ?,800 ?).A total of 192 GHPFRCC specimens(dimensions:350mm x 50mm x 15mm)categorized into 16 groups were designed,in order to investigate the effect of water-to-binder ratio,sand-to-binder ratio,PVA fiber content,fly ash content,and water reducing agent dosage on tensile strength.Results revealed the strain limit is more sensitive to high temperatures than the tensile strength.After exposure to 200 ?,reduction in strain limit is much more than that in tensile strength.Significant reduction in tensile strength occurred after exposure to 400?,and,at 800?,the specimens became too fragile to be tested.(2)Four-point bending tests of GHPFRCC prism specimens(dimensions:400 mm× 100 mm × 100 mm)were carried out after exposure to high temperatures(200 ?,400?,600?,800?).A total of 192 GHPFRCC specimens(dimensions:350mm ×50mm x 15mm)categorized into 16 groups were designed using the Mini tab software,in order to investigate the effect of the water cement ratio,sand cement ratio and PVA fiber dosage,dosage of fly ash and water reducing agent dosage on tensile strength.After exposure to 200 ?,the flexural strength is slightly reduced,while the ultimate mid-span deflection is significantly reduced.After exposure to 400 ?,the flexural strength and the ultimate mid-span deflection continue decreasing,strength continued to decline.After exposure to 800 ?,the remaining flexural strength and ultimate mid-span deflection are only up to 10%of those before high temperature exposure.But due to the pathway created by fiber melting for releasing vapor pressure,spalling did not happen.(3)Fire test of 10 GHPFRCC frame beams were performed by applying fire at three faces of beam specimen following the IS0834 standard temperature profile.Thermocouples and displacement sensors were respectively embedded in the beams and attached on the beams,in order to monitor the temperature and mid-span deflection.The results indicate that the bottom corners of cross sections of the test beams have the highest temperature increasing rate and the center has the lowest increasing rate.The mid-span deflection of test beam approximately linearly decreases,and high temperature accelerates the deflection changes.The primary influencing factor of the failure mode is the shear-to-span ratio.Longitudinal reinforcement ratio can improve the shear capacity of GHPFRCC beams.Stirrups have significant effects on the shear performance of GHPFRCC frame beams.