Possibilities of improving crushed sand performance in fresh concrete by washing: a case study.

The paper presents an industrial case study where possibilities of removing the excess of fines from crushed sand are investigated in full-scale sand washing experiments. The results are in line with previously reported investigations on laboratory scale, and indicate that the used washing technique primarily reduced the amount of material in size fractions below about 250 µm with emphasis on particles smaller than about 30 µm. This suggests that similar results can be expected from any similar and simple aggregate washing processes where basically only the Stoke's law principle is utilised for classification purposes. Concrete with the crushed washed fine aggregate displayed significantly better workability in terms of higher slump and slump-flow values compared to the corresponding mixes with the unwashed crushed sand. This is a direct result of removal of the finest particles, which are decisively contributing to the reduced flowability of the cement paste matrix of the concrete through their excessive water demand due to the large specific surface area. [ABSTRACT FROM AUTHOR]