Flexural Fatigue Performance of Concrete Prepared with Low-Heat Portland Cement

To investigate the influence of cementing materials on the fatigue performance of concretes, the flexural fatigue performance of concretes prepared with low-heat Portland cement and ordinary Portland cement at different stresses was studied by a four-point bending fatigue test method. Additionally, the relationship between microstructure and fatigue performance was studied by using DTA-TG, SEM, and MIP methods. It was observed that in comparison to the ordinary Portland cement, the low-heat Portland cement is favourable for the improvement of the fatigue life of the concrete under the same stress lever (0.75–0.90). As the curing age was extended from 28 days to 180 days, the flexural fatigue life of both the kinds of concrete with a loading of 3.49 MPa was increased by 230 452 times in low-heat Portland cement concrete and 8 168 times in case of ordinary Portland cement concrete. The fatigue life of low-heat Portland cement concrete on the 90th day and 180th day was 4.76 and 19.88 times higher than that of ordinary Portland cement concrete, respectively. The longer the curing age the better the anti-fatigue performance of low-heat cement concretes. The microstructure study indicated that low-heat Portland cement concrete consisted more C-S-H gel and less Ca（OH）₂. Furthermore, low-heat Portland cement concrete had lower increase (less than 10%) on the most probable pore size; and the proportion of large pores after fatigue loading reduced the crack propagation and enhanced the anti-fatigue performance.