Deleterious Materials & Organic Impurities — Part 2
Part 2 covers deleterious materials — silt, clay and fine dust, organic impurities, and other harmful constituents. Silt/clay coatings reduce paste–aggregate bond and inflate water demand; organic matter retards setting and reduces strength. These are judged against the IS 383 limits and are a common, cheap-to-check cause of weak, unpredictable concrete.
Key Requirements
•Silt/clay/fine-dust content limited (washing/sedimentation tests) — judged vs IS 383
•Organic impurities test (colour comparison) — flags set-retarding organic contamination