Fire Performance Of Green High Performance Fiber Reinforced Cementitious Composites Frame Column

Green High Performance Fiber Reinforced Cementitious Composites(GHPFRCC)is developed based on Engineered Cementitious Composite(ECC)by using high-volume fly ash and employing suitable amount of Polyvinyl Alcohol(PVA)fibers.The GHPFRCC has good deformability,toughness,energy absorption capacity,and crack extension ability,which can be used to enhance the seismic performance and durability of structures effectively.In this study,the mechanical properties of GHPFRCC after exposure to high temperature and temperature fields in GHPFRCC frame columns subjected to fire are studied.(1)The compressive strengths and the Poisson's ratios of 16 GHPFRCC mixtures before and after exposure to high temperatures(200 ?,400?,600 ?,and 800?)are investigated.The influences of water-to-binder ratio,sand-to-binder ratio,PVA fiber content,fly ash content,and superplasticizer content on the compressive strength and Poisson's ratio are evaluated.After 200?,the mass loss is 5.5%-10.3%,the compressive strength is reduced by 0.1%-13%,and the Poisson's ratio is 0.15-0.32.After 400?,the mass loss is 6.2%-15.5%,the compressive strength is reduced by 4%-49%,and the Poisson's ratio is 0.1-0.2.After 600?,the mass loss is 6.6%-19.7%,the compressive strength is reduced by 24%-57%,and the Poisson's ratio is 0.1-0.17.After 800?,the mass loss is 9.1%-18.6%,the compressive strength is reduced by 44%-82%,and the Poisson's ratio is 0.06-0.16.(2)The Young's moduli of 16 GHPFRCC mixtures before and after exposure to high temperatures(200?,400?,600?,and 800?)are investigated.The influences of water-to-binder ratio,sand-to-binder ratio,PVA fiber content,fly ash content,and superplasticizer content on the Young's moduli are evaluated.The Young's modulus of GHPFRCC is about 12-23 GPa after 200?,10-18 GPa after 400?,7-12 GPa after 600?,and 2.4-6.0 GPa after 800?.The mix proportions are optimized regarding to the Young's modulus for each temperature.The water-to-cement ratio,sand-to-binder ratio,and PVA fiber content,fly ash content.and superplasticizer content are respectively 0.32,0.36,1.7%,65%,and 0.15%for 200?,0.32,0.36,1.5%,60%,and 0.1%for 400?,0.24,0.66,1.5%,60%,and 0.1%for 600?,and 0.24,0.36,1.5%,60%,and 0.1%for 800?.(3)The constitutive relationships of 16 GHPFRCC mixtures before and after exposure to high temperatures(200?,400?,600?,and 800?)are investigated.The influences of water-to-binder ratio,sand-to-binder ratio,PVA fiber content,fly ash content,and superplasticizer content on the constitutive relationships are evaluated.The compressive strength of GHPFRCC slightly changes between 25 ?and 200?,and then,while temperature is in the range of 200-800?,the compressive strength is significantly reduced.The compressive strength can be changed by adjusting the water-to-binder ratio of GHPFRCC.The constitutive curve can be divided into two phases:the rising and the descending phases.The GHPFRCC mixtures have adequate ductility at 25 ?-200?,but become brittle at 400 ?-800?.(4)Fire performance of GHPFRCC frame columns is evaluated.Typically,the failure mode of GHPFRCC frame column is splitting fracture,with a longitudinal crack from the bottom to the top of column.A large axial compression ratio leads to more severe damage.GHPFRCC frame columns subjected to fire at all four faces sustain good integrity;however,in three-face fire scenarios,the face opposite to the insulation face is prone to spalling of the protective layer.GHPFRCC frame column demonstrated better fire resistance than ordinary concrete and high strength concrete columns.The temperature increasing rate is the highest at the corners of cross section,followed by the center of fired face,and followed by the corners of the three-face fired scenario,and the slowest at the center of cross section.With the same axial compression ratio,the GHPFRCC column without stirrups subjected to fire at all four faces has the largest axial deformation.