This paper presents the findings of an investigation of the fiber content variations in concrete being discharged from a\nready-mix truck at the construction site. Concrete samples were extracted from the truck drums at the beginning, middle and end of\ndischarge. Subsequently, fibers in each sample were separated from the concrete, and weighed. Presumably, synthetic macro fibers\nwill float towards the top, i.e. towards the drum opening, of the inclined, revolving truck-drum, while, on the other hand, steel\nfibers will tend to gravitate towards the lower parts of the mixer drum. Accordingly, the discharge batch, containing synthetic\nmacro fibers, will contain a higher amount of synthetic fibers per unit volume at the start of discharge than the average unit volume\nfiber content of the mix, and the content will gradually decrease further down the batch. The discharge batch of steel fiber concrete\nwill contain fewer fibers per unit volume at the start of discharge than the average unit volume fiber content of the mix, and the\ncontent should gradually increase further down the batch. The correctness of the foregoing is partly confirmed. A certain\npercentage of the truck loads did not comply with the proposed requirements, mainly steel fiber reinforced batches, indicating the\nnecessity of a code or guideline amendment. A change in the Norwegian shotcrete directive was made in 2011, based upon\nexperimental research work (2010), which, in combination with the subsequent University of Life Sciences report (2012),\nconstitutes the foundation of this article.
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