Research On Concrete Mixture Design Method Based On Aggregate Gradation Optimum

Aggregate is the important ingredient of concrete. It accounts about65%-80%for total volume in the ready mixed concrete. As quality natural aggregate resources are exhausting with massive construction development in recent years, while the quality of manufactured aggregate is still poor. Furthermore, the ready mixed concrete industry of our country is lacking of attention to aggregate in the practical production process. For all this reasons, result in high paste content, poor workability, durability and costly in our concrete. Besides, that’s also a serious restriction of concrete quality improvement and new technology application.Contemporary concrete is place more emphasis on workability, therefore, the gradation of aggregate composition has been put forward higher requirements than before. However, the survey in the mixing plants of Beijing, Tianjin, Hebei regions indicated that inferior aggregate which gradation is extremely poor are still used in the production. In addition, due to the aggregate source is diversity, it’s easy to effect the quality of raw aggregate, which cause the difficulty to control the aggregate gradation and rapidly adjust to concrete proportion in the practical production process.In view of the above problems and. combined with the actual situation of ready mixed concrete production in our country, this study based on the analysis and understanding of document about gradation theory and concrete mix design, then proposed a method to obtain relatively reasonable aggregate gradation on the present raw materials condition. The main approach is using blended aggregate in concrete. At the same time, in order to ensure the rationality of combined aggregate gradation, also proposed the key control points from three aspects, including the application of maximum density curve, following the recommendations of individual percent retain on each sieve by ACI, and comfort zone about Coarseness factor-Workability factor (CF, WF). Finally, hope to provide a theoretical guide for engineering practice.Enormous experimental study and engineering practices indicate that this m ethod is reliable to ensure the combined aggregate reasonable gradation on con dition that optimum use of existing raw materials. In the premise of ensuring the strength and workability, reduce the paste content, improve the durability and reduce costly effective. In addition, in this study also utilizes PC software to solve concrete aggregate combination conveniently and precisely, it’s condu cive to the computerization of concrete mix design and has a broad application prospect.