Influence of steam curing on compressive fatigue performance of high-volume slag concrete

Compressive fatigue generally causes permanent internal damage to concrete structures. This paper presents an experimental study to evaluate the influences of steam curing and slag replacement on the compressive fatigue performance of concrete. After 10 000 cycles loading at stresses of 0·5, 0·6 and 0·7, the residual compressive strength of concrete was measured to investigate the mechanical property after fatigue. The fatigue damage was determined using two non-destructive techniques: the ultrasonic pulse velocity and electrochemical impedance methods. In the electrochemical impedance method, the R₁ and n parameters fitted from the R_e(CR₁(QR₂)) circuit model were used to characterise the pore structure. The results showed that the residual compressive strength of standard-cured concrete without slag replacement decreased with increasing stress. The compressive fatigue damage of specimens after steam curing was greater than that after standard curing. In steam curing conditions, the fatigue damage of concrete increased with increasing slag replacement. The results indicated that electrochemical impedance is an appropriate method to evaluate compressive fatigue damage.