The ash content which gives an indication of inorganic constituents is determined by igniting the admixture at 6000C to remove any organic material. 

Reference Standards

IS : 9103-1999 – Concrete admixtures specification

Equipment & Apparatus

  • Oven(3000C)
  • Bottle
  • Balance(0-10kg)


  1. 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 90C to remove the liquid portion by evaporation.
  2. 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 300C in 1 h and 600C in a further 2 to 3 h period. The temp of the furnace is maintained at 600±25C for 16 to 24 h.
  3. 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

admixture ash content 1


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.

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