Research On Concrete Vibration Mixing Mechanism And Industrial Application

At the present time, the focus of concrete research at home and abroad is materialgraduation, material performance and fresh concrete molding, but not the mixing process.The reason is that the mixing process involves mixing equipment, mixing materials andconstruction technology which belong to different disciplines, and easily divorced from eachother during the research process, so the study of mixing process is still at the macroscopicscale up to now, and this results in some problems, such as poor microstructure uniformity,low interfacial bond strength, low mixing speed, long mixing time, mixing velocitygradient and mixing inefficient zone and so on. The author in this paper presented a newvibratory mixing method with the combination of forced mixing, placing a vibration exciterthat designed by dynamic balance principle in the middle of mixing tube, and thevibrational energy from the exciter will be fully absorbed by mixtures. This new methodcould improve the micro structure and mechanical properties of concrete and thecomprehensive performance of mixing equipment.Firstly, the author analyzed the rheological properties of fresh concrete and provided atheoretical basis for determining the parameters of vibratory mixing equipment workingmechanism that ensure the complete destruction of the mixing mixtures structure as the goal.The shortcomings of ordinary forced mixing process were analyzed furtherly, and severalauxiliary methods to improve concrete performance were introduced.The mechanisms that vibratory mixing method to improve mixing process and concreteperformance were detailed from six aspects, such as the mechanism of vibratory mixinginfluence on concrete rheological characteristics, the failure mechanism of cement aggregatesby using vibratory mixing method, the cleaning mechanism of coarse aggregate surface andenhancement mechanism of concrete bond strength by means of vibratory mixing, thegenerating mechanism of air bubble under the action of vibration, and the improvingmechanism of mixing inefficient zone during mixing process by means of vibratory mixing,the adaptability mechanism of vibratory mixing on multi material. The analysis found that thecomprehensive performance of concrete can be improved by means of vibratory mixing.On the basis of theoretical analysis, a vertical shaft type vibratory mixer and a doublehorizontal shaft type vibratory mixer were designed. The vibration device and mixing device of the former mixer is independent from each other, but the latter is a whole. However, bothprototypes could realize vibrating action while mixing materials. The study of vibrationmixing on multi material’s adaptability was conducted in lab. The materials include ordinaryconcrete, roller compacted concrete (RCC), steel fiber reinforced concrete (SFRC), cementasphalt mortar (CA). Some tentative conclusions about reasonable value of the vibratory andmixing parameters were reached, and these will provide the basis for the industrializedapplication. The test results indicated that vibratory mixing has better adaptability to multimaterial and the concrete performance indexes are better than ordinary forced mixing. Thevertical shaft type vibratory mixer is more suitable for mixing materials with smaller particlesize, such as cement asphalt mortar, and the double horizontal shaft type vibratory mixer ismore suitable for mixing materials with larger particle size.Based on the theoretical analysis and experimental study, the irrationality of the currentevaluation index system of mixing equipment was tested and analyzed in this paper, andsome suggestions for revising the current evaluation index system were put forward, such as,what kind of indexes will be needed in different situations, in order to improve the indexsystem.In order to combine the research findings of theory and test with industrial practice, aindustrial prototype, a double horizontal shaft type vibratory mixer with1m3capacity, wasdesigned and manufactured, and the industrialization research was proceed. The studies showthat the prototype is stable and reliable during the working process with lower energyconsumption, vibration mixing time of45s and each index meets the national standard.Under the same conditions the strength of concrete produced by industrial prototype is15%higher than ordinary forced mixer, and the homogeneity of fresh concrete produced byindustrial prototype is better. In the case of reducing cement15%, the performance ofconcrete produced by industrial prototype is still meet the design requirements, so the effectof saving cement is obvious.The research is assisted by National Science Found (50678026) and Major ScientificTechnological Innovation Special Fund Project in shaanxi province（2008ZKC01-16）.