Abstract:Three point bending method is the most common one used to determine the fracture energy of concrete, for this method does not require very complicated testing machine. But there may be some error sources in the three point bending testing set up as pointed out by other researchers. So in this paper, on the basis of analysis of the error sources in the three point bending testing set up, improvement of the testing system was made. It was found that the accuracy of measured load deflection curves using the improved testing system was much better than that by using unimproved testing system. Nevertheless, the calculation of the area under the tail of the load deflection curve can also influence the accuracy of the determination of fracture energy of concrete. And some researchers have found that the assessment of this area according to RILEM (50 FMC) is not very proper. Therefore, in this paper, by analyzing the form of the tail of the load deflection curve, the influence of the tail of the curve on the determination of the fracture energy was studied, and then the measured results of fracture energy were calibrated. It was found that after calibration the fracture energy does not have size effect any more.
