Tests on the Compressive Fatigue Performance of Various Concretes

In the present study, six concrete mixtures were prepared to examine the effect of the types of binder and concrete on the fatigue performance of concrete under compression. The selected binder types include ordinary portland cement (OPC); high-volume supplementary cementitious material (SCM) composed of 30% OPC, 20% fly ash (FA), and 50% ground granulated blast-furnace slag (GGBS); and alkali-activated (AA) binder composed of 50% FA and 50% GGBS activated by the combination of ${\mathrm{Na}}_2{\mathrm{SiO}}_3$ and $\mathrm{Ca}{(\mathrm{OH})}_2$. Using the prepared binders, normal-weight concrete (NWC) and lightweight concrete (LWC) with a unit weight of $\mathrm{1,700}\mathrm{kg}/{\mathrm{m}}^3$ were produced. For cyclic loading of concrete samples, the constant maximum stress level varied among 75, 80, and 90% of the static uniaxial compressive strength of concrete, whereas the constant minimum stress level was fixed at 10% of the static strength. On the basis of a regression analysis conducted using test results, the fatigue life and fatigue stress-strain curve for concrete were formulated to evaluate the incremental strain with the number of cyclic loading. Test results clearly showed that the fatigue life of LWC tended to be slightly lower than that of the companion NWC, whereas the incremental fatigue strain in LWC was higher than that in NWC. These observations were more pronounced for concrete mixtures using high-volume SCM or AA binders than for OPC concrete. The proposed fatigue stress-strain model provides good mathematical simplicity and accuracy in predicting full fatigue stress-strain curves for concrete and/or a single piece curve at a certain number of cycles, without the need for a tedious step-by-step calculation procedure.