| At present, the constructions of hydropower projects in China are mainly concentrated in the west. The characteristics of this area are complex conditions of geography and geology, high mountains and steep slopes, and deep covering layers, etc. Because of the large scales and discharge flow of these projects, the discharge structures face impacts, abrasions and cavitation damages from high water head, big flow and high-speed flow. Generally, in order to improve abrasion-resistance and anti-cavitation capacity of concrete, it is more considered that improving the concrete strength. However, the content of gelled materials will be increased, which will increase the risk of cracking and reduce the durability of concrete.Therefore,it is significant to study on cracking resistance of hydraulic abrasion-resistant concrete.The influences of different types of silica fume, fibers and different dosages of fly ash on abrasion-resistance and cracking-resistance capacity are studied in this paper. By means of Scanning Electron Microscopy (SEM), X-ray diffraction analysis (XRD), and water-absorbing dynamics, analysis on microstructure of cement stone with different silica fume dosages and fiber types are made. The gray system theory is applied to value the comprehensive performance of abrasion-resistance concrete.From the study results, it is indicated that the abrasion-resistance strength of concrete mixed with silica fume is higher and increase significantly with the increasing of age. The effects of different silica fume types on abrasion-resistance strength of concrete are different:the effect of Fuxiang silica fume is the worst, and the different of other three types are not significant. Concrete with silica fume is more likely to generate plastic cracking, and the effects of different silica fume types on cracking-resistance capacity are same basically. The abrasion-resistance strength of concrete with fibers is significantly improved, and the effect of fiber types on which is small. Moreover, the tensile strength of concrete can be improved by mixing with fibers, as well as the brittleness will be reduced. Plastic shrinkage cracking of concrete can be inhibited significantly by fibers. By the increasing of fly ash contents, the abrasion-resistance strength of concrete will be reduced and the cracking-resistance capacity will be better.On the one hand, as a kind of auxiliary gelled material, silica fume is mixed into cement paste and occurs secondary hydration reaction with Ca(OH)2, then the C-S-H gel contents increase. On the other hand, pores can be filled with silica fume. For these reasons, hardened cement paste and concrete will be denser and the strength will be higher.The gray system theory is applied to value the comprehensive performance of abrasion-resistance concrete. Mixing with silica fume and fiber can play their respective advantages better, which can improve abrasion-resistance strength as well as cracking-resistance capacity. |
