The ash content which gives an indication of inorganic constituents is determined by igniting the admixture at 6000C to remove any organic material.
IS : 9103-1999 – Concrete admixtures specification
Equipment & Apparatus
- About 1 g of sample is placed in a porcelain crucible. The crucible is then placed over a steam water bath or an air oven at 900 C to remove the liquid portion by evaporation.
- Then the solid contents with the crucible is transferred to a muffle furnace at room temperature and is heated gradually so that the temperature reaches 3000 C in 1 h and 6000 C in a further 2 to 3 h period. The temp of the furnace is maintained at 600±250 C for 16 to 24 h.
- The crucible is removed from the furnace and allowed to cool. After cooling for 30 min the crucible plus lid and contents is weighed to the nearest 0.001 g.
Calculate the ash content in the original mass of the admixture
Weight of crucible and lid = W1
Weight of crucible, lid and sample = W2
Weight of crucible, lid and ash = W3
The result is reported to nearest whole number.
Safety & Precautions
- Use hand gloves while removing containers from oven after switching off the oven.
- Equipment should be cleaned thoroughly before testing & after testing.
- To check electric supply of the instrument.
- To wear safety shoes & aprons at the time of test.