Fracture characteristics of recycled aggregate concrete using work-of-fracture and size effect methods: the effect of water to cement ratio

A correct understanding of the fracture mechanism of Recycled Aggregate Concrete (RAC) plays an important role in the design of RAC structure and also in gaining a better understanding of the behavior of structures made from it. On the other hand, one of the most important parameters that affects cracking behavior and the fracture parameters of concrete is the water to cement ratio. The main objective of this study is to investigate the effect of different water to cement ratios on the fracture behavior of RAC. To achieve this objective, 125 notched concrete beams were subjected to three-point bending experiments, with W ranging 0.35 to 0.7. Specific fracture energy (G_F) and characteristic length (L_ch) from work-of-fracture method and initial fracture energy (G_f), brittleness number, fracture toughness, effective length of fracture process zone (C_f), and the critical crack-tip opening displacement from size effect method were evaluated. The results illustrate that G_F and G_f increase by 34 and 64% when W reduces from 0.7 to 0.35, respectively. Moreover, L_ch and C_f reduce from 378 to 208 mm and from 32.5 to 17.2 mm by decreasing W from 0.7 to 0.35, respectively. On average, G_F/G_f ratio for various Ws attains 2.48 with the variation coefficient of 10.9%. Eventually, multivariate prediction models were developed for RACs with various Ws. A comparison was made between prediction and experimental values of the present and previous research works.