# High-Frequency Fatigue Testing of Recycled Aggregate Concrete
## 3 Results and Discussions
### Influence of the Number of Cycles Per Step during a Locati Test
For this reason, it can be assumed that the influence of increasing the number of cycles per step during a Locati test was small given that the difference between steps had a greater influence than increasing the number of cycles per step by 150%. Figure 11 shows the influence of increasing the frequency on the fatigue behaviour of the RC-S by comparing RC-S-HF-\(2\times 10^{5}\) with RC-S-MF-\(2\times 10^{5}\). As in RC-B, it can be concluded that, in the first phase, increasing the test frequency had no impact on the deformation suffered by the specimens. From step 2, it can be seen how the two curves split, increasing more rapidly in the case of the RC-S-HF-\(2\times 10^{5}\). This effect was more severe in RC-S than in RC-B, which was reflected by a greater variation in the IC of RC-S as the test frequency increased. Figure 11 shows the influence of increasing the number of cycles per step from \(2\times 10^{5}\) to \(5\times 10^{5}\) for RC-S. A similar behaviour to that of RC-B was observed, but in this case, the effect of increasing the number of cycles per step was greater than in RC-B, which was reflected in the accelerated separation of the curves. As in the case of RC-B, in this case, the greatest difference in fatigue limit was found between RC-B-HF-\(2\times 10^{5}\) and RC-B-HF-\(5\times 10^{5}\) and was one step; for this reason, it can be assumed that the influence of increasing the number of cycles per step during a Locati test was small, given that the jump between steps had a greater influence than increasing the number of cycles per step by 150%. Figure 10: Comparison of the maximum strain of the RC-B for a Locati test with \(2\times 10^{5}\) cycles per step at a low frequency (RC-B-MF-\(2\times 10^{5}\)), a Locati test with \(2\times 10^{5}\) cycles per step at a high frequency (RC-B-HF-\(2\times 10^{5}\)) and a Locati test with \(5\times 10^{5}\) cycles per step at a high frequency (RC-B-HF-\(5\times 10^{5}\)). In Figure 12, both the frequency and number of cycles affected the fatigue life during the Locati RC-M test. The behaviour of this material was an intermediate situation between RC-B and RC-S, being in all cases, more similar to the behaviour of RC-B. Figure 11: Comparison of the maximum strain of the RC-S for a Locati test with \(2\times 10^{5}\) cycles per step at a low frequency (RC-S-MF-\(2\times 10^{5}\)), a Locati test with \(2\times 10^{5}\) cycles per step at a high frequency (RC-S-HF-\(2\times 10^{5}\)) and a Locati test with \(5\times 10^{5}\) cycles per step at high frequency (RC-S-HF-\(5\times 10^{5}\)). Figure 12: Comparison of the maximum strain of the RC-M for a Locati test with \(2\times 10^{5}\) cycles per step at a low frequency (RC-M-MF-\(2\times 10^{5}\)), a Locati test with \(2\times 10^{5}\) cycles per step at a high frequency (RC-M-HF-\(2\times 10^{5}\)) and a Locati test with \(5\times 10^{5}\) cycles per step at a high frequency (RC-M-HF-\(5\times 10^{5}\)). To summarise, it can be stated that performing tests at a very high frequency reduced the number of cycles that a specimen was capable of resisting compared to performing the test at a moderate frequency. On the other hand, it was also demonstrated that \(2\times 10^{5}\) cycles per step was enough to characterize a fatigued concrete.