Effects of Aggregate Size and Water-to-Cement Ratio on Fracture Energy of Normal Weight Concrete

In the use of fracture mechanics to concrete, one of the most important parameters describing the fracture behavior of concrete is fracture energy (GF). Concrete is a composite material with a very complicated nonlinear fracture zone behavior. Consequently, a property of hardened concrete is strongly influenced by its constituent materials properties, interactions, and proportions they are combined. The aggregate typically occupies more than half of the concrete mix and plays a significant role in determining the fracture behavior of concrete. In these regard, understanding the fracture behavior of concrete based on its aggregate size distribution and water-cement ratio is important. In this study, the effects of maximum coarse aggregate size (dmax) and the water-to-cement ratio on fracture energy of normal weight concrete are investigated experimentally by a series of a three-point bending test (3-PBT). The beam specimens were cast using two nominal maximum aggregate size distributions (9.5 mm and 12.5 mm) and two water-cement ratios (0.5 and 0.6). The tests were performed in displacement control electrohydraulic servo universal testing machine at a constant displacement rate of 0.2 mm/s. Then, the fracture energy was analyzed by the work of fracture method (WFM). The experimental results show that increasing the nominal maximum aggregate size from 9.5 mm to 12.5 mm, the fracture energy increases by 50.34% when water-to-cement ratio is fixed at 0.5 and by 12.52% when the water-cement ratio is 0.6. Moreover, by using experimental results comparison made with existing empirical methods for determining the fracture energy of concrete. The comparative study reveals that existing empirical models underestimated the fracture energy obtained experimentally by work of fracture method for normal weight concretes of this study.