High Volume Fly Ash Concrete Breaking

With the development of structural analysis and design methods, the study on mechanism of fracture of concrete has been widely and seriously taken. The paper is about this field and focuses on the following subjects.Firstly, with the three-point bend tests on notched beams whose sizes are 1000×200×100mm3, the influence of the initial notch-to-depth ratios (a0/d) on fracture parameters of high-volume fly ash concrete, which are 0.3, 0.4 and 0.5, is studied. According to the results, the pre-critical crack propagated length ( a) and critical crack tip opening displacement (CTODc) have no change and the fracture toughness (K1c), equivalent fracture toughness (KSIC) and fracture energy (GF) decrease with the increase of a0/d.Secondly, the relationship between specimen strength and fracture parameters is studied with the same size beams as above. The results show that the fracture toughness, equivalent fracture toughness and fracture energy all increase firstly, and then decrease with the increment of specimen strength.Thirdly, the fracture surfaces of ruptured specimens have fractal properties and the fractal dimensions-fracture toughness relationship has been obtained by measuring the fractal dimensions of fracture surfaces. It shows that the logarithms of fracture toughness decrease with the increase of fractal dimensions.Finally, the paper investigates how the volume content of polypropylene fibers affects the fracture parameters of high-volume fly ash concrete. The results show that the fracture toughness, equivalent fracture toughness and fracture energy tend to increase, the critical crack tip opening displacements tend to decrease, and the pre-critical crack propagated lengths are not stable with the increase of the volume content of polypropylene fibers...