Injurious organic impurities
The fine aggregate is placed into a glass bottle with a 3% sodium hydroxide solution. The mixture is shaken vigorously and allowed to stand for 24-hours. The color of the supernatant liquid then compared with standard colors. If the color of the solution is darker than the Organic Plate No. 3, the aggregate is considered to contain organic impurities that may be injurious to concrete.
Organic, Impurities, Injurious