Crushing Value Characteristics Of Gneissic Coarse Aggregate And Influence On Properties Of Concrete

Coarse aggregate accounts for 50% in the volume of concrete and plays an important role in concrete structure, whose strength has a great influence on the mechanical properties, the volume stability and the durability of hardened concrete. This dissertation is serviced to the construction of Wu Ying expressway. The characteristics of gneissic coarse aggregates crushing value and influence law on mechanical properties, shrinkage property and durability of hardened concrete are studied to present the crushing value of gneiss coarse aggregates suitable for concrete in Wu Ying expressway construction and provide theoretical basis for application of gneissic coarse aggregate in concrete.The lithofacies, alkali-silica reaction and mechanical properties of coarse aggregate along the expressway are tested. The results indicate that its qualities satisfy relevant criterions and can be used in concrete project. New correlative formula between JTG E42-2005 and JTJ 041-2000 is founded by 19 kind of gneissic coarse aggregate crushing values. Particle shape, percentage of flat-elongated particles and gradation of coarse aggregate can produce remarkable influence on crushing value.The effects of the crushing value on the mechanical properties of concrete with the target strength grades of C30, C60 and C80 are respectively investigated. Six gneissic coarse aggregate with the crushing values ranging from 9 to 24% and a limestone coarse aggregate are used in the tests. The the results reveal that relation is not remarkable between gneissic coarse aggregate crushing value and gneissic coarse aggregates crushing value has little relation to compressive and splitting tensile strengths of concrete, but a great influence on the flexural strength and elastic modulus of concrete. The difference in compressive and splitting tensile strengths is little between concrete respectively prepared with gneiss and limestone coarse aggregate, of which crushing values are proximalis, but the flexural strength and elastic modulus of concrete prepared with gneiss coarse aggregate are both lower than it with limestone coarse aggregate, especially elastic modulus. According to the related criterion, the gneissic coarse aggregate whose crushing values under 14.4% translated by correlative formula in T0316-2005 can be used in C40-C60 concrete in superstructure of bridge.Drying shrinkage and frost resistance property of C60 concrete prepared with four kind of gneiss coarse aggregate are studied. the results show that gneissic coarse aggregates crushing value has a great influence on the drying shrinkage value and little relation to frost resistance property of concrete.