Stable-coloured, glass standard for long-term use
|Other Standards||ASTM C40|
- The colour standard is designed for quick and accurate tests of organic matter in sand and aggregates for concrete, according to ASTM C-40.
- Organic impurities, usually in the form of tannic acid and its derivatives, are typically present in fine aggregates such as sand.
- These may interfere with the chemical reactions of hydration and may affect the strength of the cement, mortar or concrete where the aggregate is being used.
- The results given by the colour comparison are designed to serve as a warning that unacceptable levels of organic impurities may be present.
- In the test, a measured sample of fine aggregate is shaken with sodium hydroxide solution in a stoppered bottle and left to stand for 24 hours.
- The liquid above the test sample develops a colour, which is compared directly with coloured glass standards to indicate the level of organic impurities present.
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