Usually, the truck agitator is used to transport fresh concrete which is mixed at a concrete plant. In case of placing of concrete at a construction site, discharging efficiency of the truck agitator influences on construction efficiency and quality of concrete. In this report, we observed flow of fresh concrete in agitator, while we can't observe untill now, with help of the visualization technique, and investigated about influence of blade rolling pitch angle and rotational speed on discharging efficiency. As a result, it was cleared that the agitator can have most suitable angle for discharging efficiency, and that the higher sliding resistance between concrete and surface of blade, the lower discharging efficiency.
