The ribbon concrete mixer with double barrels is commonly used to improve the uniformity of the fresh concrete in construction industry. In order to investigate the mixing efficiency of this kind of ribbon concrete mixer, a discrete element method was used to simulate the mixing process of fresh concrete. Firstly, a discrete element model of the fresh concrete was established by using the Hertz?Mindlin with JKR contact method. The experiment processes, i.e. slump test, L box test and rheometer test were simulated by using this discrete element model and its parameters, and the simulation results were compared with the experimental ones to verify these model parameters. Afterwards, the mixing efficiencies under different initial loadings were investigated and the mixing efficiency under top?bottom loading was highest. Under each initial loading, the mixing efficiency of the fresh concrete in mixer's left region and front region was almost the same as that in their opposite regions respectively, while the mixing efficiency in the upper region was much higher than that in the lower one. Besides, a mixing blind area was found near the outlet in the bottom of the mixer, and the method of discarding the initial concrete discharge was proposed to improve the uniformity of fresh concrete. In addition, the effects of rotational speed on the mixing efficiency were investigated, and it was found that the mixing efficiency with a larger rotational speed tended to be higher. However, their mixing efficiencies were almost the same at the same rotation number of impeller. This numerical model and results provided an effective approach to solve the concrete mixing problems in industry and some scientific references for improving the mixing efficiency of a double ribbon concrete mixer.
Zechu LIAO Wei GAO Lei LIU Shengqiang JIANG Yuanqiang TAN
. Mixing efficiency of a concrete ribbon mixer and DEM simulation[J]. The Chinese Journal of Process Engineering, 2019
, 19(4)
: 668
-675
.
DOI: 10.12034/j.issn.1009-606X.218307
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