Research On Mixing Inefficient Zone And Its Eliminating Methods

Forced action concrete mixer has developed along with the development of concrete and construction technique. In the current concrete mixing equipment, this type of mixer has been widely used for its advantage of high mixing quality and productivity. Mixing inefficient zone is the inherent defect of the forced action mixer, which seriously affects the mixing quality and efficiency. However, there is no knowledge and corresponding research on the problem of inefficient zone in the world at present. For solving this problem, the causation and eliminating methods of the inefficient zone were studied.This thesis began with concrete mixing theory, analyzed one-sidedness of traditional mixing concept. According to the movement of concrete mixture and the mutual effect-relation between the mixing mechanism and mixture in the mixing process, a new mixing concept was put forward. It is considered that a good combination of countercurrent and diffusive movement need to be obtained for the mixture in the perfect mixing process. On the basis of the new mixing concept, a new criteria system for performance assessment of concrete mixing equipment was established, which used uniformity and strength of concrete as testing indexes.Starting from structure of the mixer and rheological characteristics of concrete, the causation of inefficient zone for the forced action mixer was analyzed. Velocity gradient of the mixing mechanism was revealed. According to the new mixing concept, parameters optimization of mixing mechanism, vibratory mixing method and the structure of double-row blades were used to solve the problem of inefficient zone. Elimination principle and effect of different methods were discussed. The results indicate that it is necessary to use auxiliary means or improve the existing structure of the mixer for effectively eliminating the inefficient zone.Experimental prototypes of vibratory mixer and double-row blades mixer were designed based on double-horizontal shafts mixer. By theoretical analysis andexperimental research, the influence of working-mechanism's parameters of the corresponding mixer on mixing quality was studied, and rational range and matching relationship of parameters were recommended. Finally, working performance was tested, and comparison of each prototype with the forced action mixer was made. The experimental results show that the methods of vibratory mixing and double-row blades can eliminate the inefficient zone, and improve mixing quality and efficiency.At last, industrial application of the eliminating methods was presented. Industrial prototypes of vibratory mixer with double-horizontal shafts and double-row blades mixer were designed. Based on the industrial experiment of double-row blades mixer, the feasibility and efficiency of this method was verified.