Study On Mixture And Optimization Of Fine Aggregate And Property Of Its Ready-mixed Concrete

There is a great amount of concrete consumption annually in China, but the level of green production is relatively low. In order to enhance the green production level and promote comprehensive use of sand and gravel resources, using alternative aggregates to replace nature sand and gravel to produce ready-mix concrete has been reach broad consensus, concerning green development, environmental and ecological protection. At present the application of alternative fine aggregates such as manufactured sand, tailing sand, pit sand and recycling coarse aggregates have been rapidly grown, but systemic studies on concrete performance mixed with alternative fine aggregates and its mix design approaches have not been reported. In this paper experiment have been carried out to study the theory of aggregate gradation optimization and to study the performance of concrete with the alternative fine aggregates. Based on those studies, a new concrete mix design approach has been proposed and a design and management information system has been developed. Test and analysis have shown that high performance of concrete can be got as long as aggregates gradation optimization of alternative aggregates is made.The main content of this paper include:?1? The state-of-art of concrete mix design approaches has been reviewed. A new mix design approach based on the theory of Coarseness Factor?CF? and Workability Factor?WF? has been proposed and studied. This approach is focused on solving the alternative aggregate gradation optimization in concrete composition. The properties of alternative aggregates are remarkably different from nature aggregates. Using the WF-CF optimization approach to decide the optimal amount of multiple alternative aggregates in concrete composition, high performance concrete should be got.?2? The influence of WF and CF of aggregates on the workability and compressive strength of concrete has been studied and analyzed. In order to get good workability and strength of ready-mix concrete, the favorable range of WF and CF has been studied and discussed in this paper. Then the study has been carried out on the optimization of the concrete mixture with this theory, and the result shows that the concrete with its slump remaining 180 mm can be made respectively with the amount of cementitious material reducing from 390 kg/m³ to 330 kg/m³ and the water-binder ratio reducing 0.46 from 0.43.?3? The combination use of the manufactured sand and the pit sand has been studied with orthogonal experiment, and the optimal level of mortar-to-aggregate ratio, sand-ratio and the substitution rate of the pit sand has been analyzed by range analysis. The result shows that the combined aggregate can meet the performance of concrete when the mortar-aggregate ratio is 32.5:62.5; although the concrete with the mixture of manufactured sand and pit sand has a lower resistance of chloride ion permeation, but its values are mostly less than /500×10^-14m²/s what can meet the concrete performance; and the water content of the concrete with the mixture of the manufactured sand and the pit sand is lower than that of the concrete with the mixture of the pit sand and the river sand for there is more fine particle in the manufactured sand and the less fine particle in the pit sand, which optimize the gradation of the mixed aggregate in some degree.?4? A design and management information system is developed with C# language. This system can implement its functions such as the management of the raw material information, concrete mix information, experiment information and the age of blocks. This system is built in a variety of concrete mixture design approaches, and combed with the CF-WF theory and the regulations of some specifications related to durability, the concrete mix design approaches based on the theory of aggregate's gradation optimization and the performance of concrete is archived.