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

Abstract

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 \(P_{\max }\). The specimens were unloaded after 3 months and then reloaded to 60 % of \(P_{\max}\). Time dependent COD were continuously measured by LVDTs under constant temperature of 20° and relative humidity of 60 %. The measured time dependent COD \(W_{\rm total}\) was considered as the summation of three parts, the irreversible part \(W_{\rm irr}\), the instantaneous part \(W_{\rm inst}\) and the creep part \(W_{\rm creep}\). It was observed that \(W_{\rm irr}\) 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 \(W_{\rm creep}\) is almost the same as the initial instantaneous deformation \(W_{isnt.}\) 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 \(W_{\rm irr}\) increases.