Influence of Imbalances in Charging of Cement and Water on Mixing Performance of an 8-Cubic Yard Central Plant Concrete Mixer. A Case Study

摘要

Test objectives were to determine tolerable limits of deviation from good blending of cement and water with the aggregate ingredients of the batch during charging of the mixer. Blending appeared to be and was judged to be good for normal plant performance, but test results clearly demonstrated the appearance to be false. Results clearly confirmed the highly significant influence of blending the batch ingredients during charging of large (8 cubic yard) central plant mixers with horizontal drum axis and both ends open. When blending of batch ingredients during charging of the mixer was poor, the charging imbalances resulted in imbalanced distributions in the mixed concrete, resulting in compressive strength imbalances that were in general proportional to the cement and/or water imbalances occurring in blending during charging. A quick and reliable method is needed for determining the uniformity of cement in plastic concrete, in order to effectively monitor the degree of blending of batch ingredients during charging of the mixer, and thus assure good quality control of the concrete produced. Improved central plant equipment capabilities are also needed for improved assurance of good control in the blending uniformity for cement and water during charging. (Author)