Concrete Mix design is complete science and it is based on a lot of research. Popular Mix Design method is highlighted in ACI 2011 committee report. It is a systematic approach in which user starts with defined slump and strength and some other parameters. End result gives quantities of different constituents.

Performance-based methods are also available in which engineer based on his experience selects initial proportions and modifies as needed. Both systematic and performance-based methods have certain advantages and disadvantages which will be covered in later posts.

Though mix design is a comprehensive process still it is very useful for engineers to know certain mix design concrete thumb rules which will make his life easier. Here is the list

Mix design gives concrete constituents which include coarse aggregate, fine aggregate, cement and water. Photo Source: gravelandgrow.ca

By adding 1 litre of water in 1 cubic meter of concrete mix

  1. Increase slump of about 25 mm is expected.
  2. It will decrease compressive strength of about 1.5 to 2.0 N/mm2
  3. Increase shrinkage potential of about 10%
  4. Waste as much as ¼ bag of cement

Effect of increasing concrete mix temperature by 1 celsius

  1. About 4 liters of water per cubic meter maintains equal slump
  2. Air content decreases about 1%
  3. Compressive strength decreases about 1.0 to 1.5 N/mm2

Effect of air content on concrete mix 

  1. If air content increases 1%, it will result in compressive strength decrease of about 5%
  2. If air content decreases 1%, then it will cause yield to decrease about 0.03 cubic meter per 1 cubic meter of concrete mix.
  3. If air content decreases 1%, then slump will decrease about 12.5 mm
  4. If air content decreases 1%, it will result in durability decreases of about 10%.

4 COMMENTS

  1. if we make an assumption that the mix design was w/c=0.6 with 6 bags (300kg) of cement, that means there was the water content of 180kg/cm; then 1 liter of water is added, 181kg of water content actually, we need 301.7kg of cement to keep the w/c=0.6.
    it doesn’t waste that much of cement as 1/4 bag.

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