Effect of Fiber Characteristics Parameters on Uniaxial Tensile Properties of HES-HDC and Evaluation Method of Tensile Toughness
To investigate the uniaxial tensile mechanical properties of high-early-strength high ductility concrete(HES-HDC)at different PE fiber diameters and volume fractions,17 groups of thin-plate specimens were designed and loaded under uniaxial tensile tests.The effects of PE fiber diameters(22 μm and 25 μm)and fiber volume fractions(1.00%,1.25%,and 1.50%)on stress-strain curve,tensile strength,and strain of HES-HDC specimens at different curing ages(2 h,24 h,7 d,28 d and 56 d)were investigated.A tensile toughness evaluation method suitable for the characteristics of HDC was proposed based on the test results.The results show that the HES-HDC stress-strain curve exhibits strain-hardening characteristics under uniaxial tensile loading,and the failure process is carried out with multiple cracks.The tensile strength and strain of HES-HDC at 2 h reach over 3.29 MPa and 0.88%,respectively,and the tensile strain at 28 d could remain more than 1.28%.When the fiber volume fraction is 1.00%,small-diameter fiber is beneficial to the tensile strain of specimens,while large-diameter fiber is beneficial to the tensile strength of specimens.Considering the tensile strength and strain of specimens with large-diameter fiber,the optimal fiber volume fraction is 1.25%.The proposed tensile toughness evaluation method can evaluate the tensile toughness of HDC during its whole loading process.In addition,the tensile toughness index of HES-HDC decreased with the increase of curing age,while the tensile strength coefficient increased.The tensile toughness of specimens with small-diameter fiber is higher than that of specimens with large-diameter fiber.The tensile toughness of specimens is the highest when the fiber volume fraction is 1.25%.
high-early-strength high ductility concretefiber diameterfiber volume fractionuniaxial tensiontensile strengthtensile toughness