Experimental investigation on uniaxial tensile creep behavior of cracked steel fiber reinforced concrete

This paper mainly investigates the uniaxial tensile creep behavior of pre-cracked steel fiber reinforced concrete. Hooked-end fiber RC65/60BN with fiber dosage of 80 kg/m3 was used with normal strength concrete. A suitable tensile creep frame and a pre-cracking test set-up were developed. Cylindrical specimens were pre-cracked at crack opening displacement (COD) of 0.05 and 0.2 mm respectively before the tensile creep test. The pre-cracked specimens were loaded at a load level of 30 % of the maximum pre-cracking load Pmax. The specimens were unloaded after 3 months and then reloaded to 60 % of Pmax. Time dependent COD were continuously measured by LVDTs under constant temperature of 20° and relative humidity of 60 %. The measured time dependent COD Wtotal was considered as the summation of three parts, the irreversible part Wirr, the instantaneous part Winst and the creep part Wcreep. It was observed that Wirr and the loading level have a great impact on the tensile creep behavior. For the specimens with a pre-cracking COD of 0.05 mm, the maximum creep deformation Wcreep is almost the same as the initial instantaneous deformation Wisnt. after 3 months loading. For the specimens pre-cracked at 0.2 mm, the damage evolution at the fibre/matrix interface in terms of irreversible crack opening and load level is also discussed. It is interesting to be noted that the creep deformation under load level of 30 % will not introduce extra damage even though the Wirr increases.