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Water/ Cemetitous Materials Ratio

The water / cementitious (w/c) ratio is used in both tensile and compressive strength analyses of Portland concrete cement. This ratio is found from

w / c = w m / w c

where w m = weight of mixing water in batch, lb (kg); and w c = weight of cementitious materials in batch, lb (kg).

The ACI Code lists the typical relationship between the w/c ratio by weight and the compressive strength of concrete. Ratios for non-air-entrained concrete vary between 0.41 for a 28-day compressive strength of 6000 lb/in 2 (41 MPa) and 0.82 for 2000 lb/in 2 (14 MPa). Air-entrained concrete w/c ratios vary from 0.40 to 0.74 for 5000 lb/in 2 (34 MPa) and 2000 lb/in 2 (14 MPa) compressive strength, respectively. Be certain to refer to the ACI Code for the appropriate w/c value when preparing designs or concrete analyses.


Further, the ACI Code also lists maximum w/c ratios when strength data are not available. Absolute w/c ratios by weight vary from 0.67 to 0.38 for non-air-entrained concrete and from 0.54 to 0.35 for air-entrained concrete. These values are for a specified 28-day compressive strength f c in lb/in 2 or MPa, of 2500 lb/in 2 (17 MPa) to 5000 lb/in 2 (34 MPa). Again, refer to the ACI Code before making any design or construction decisions.

Maximum w/c ratios for a variety of construction conditions are also listed in the ACI Code. Construction conditions include concrete protected from exposure to freezing and thawing; concrete intended to be watertight; and concrete exposed to deicing salts, brackish water, seawater, etc

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Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

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18 comments on "Water/ Cemetitous Materials Ratio"

Abid Hussain says:

Dear sir
i am in the process of designing a concrete mix for the main line sleepers. the required strength is
60 Mpa at 28 days. Can you suggest a suitable w/c ratio and probable ingredients of the mix. i will
be greatfull for your reply


Abid Hussain
Materials Engineer
North South Railway, KSA

admin says:

Soon we will be adding a report on this and hope that helps all !!


pascal maes says:

Dear sirs,

Congratulations, your site is extremely interesting.
I am afraid that the w/c % will have to be revised in lots of formulae due to the use of nanosilica which will be launched internationally.
a normal w/c relation will be abt. 0,3, depending the % of the nanosilica strenghts of over 80 mpa can be reached in 24 hrs., cement could be reduced or the thickness of the concrete could be reduced.
I will be glad to give you more info if wanted.
Best regards

Mark_Fitzpatrick says:

Mr. Maes,

I have recently come across this nanosilica technology and being from the United States we’re of course 2 years behind. This technology would absolutely revolutionize the concrete construction industry as a whole and I’m sure it will take years to implement specifications and testing methods before utilization of this material can be mainstreamed in the U.S.. My question is could you possibly lead me in the right direction to gaining more information about nanosilica cement and how the design and batch process will more than likely take place?

Ganesh S says:

Dear Sir;
I need W/B ratio vs. Compressive Strength Relationship chart for my dissertation purpose.It will be very helpful for me if i get it at the earliest. So pls do the needful.

Rama Kant Prasad says:

Dear Sir
What is The Best Quality of Water, For Concrete Mixing?

Best Regards

Randy Estrella Poquiz says:

If you can drink the water that’s the best for concrete mix.

kibrie says:

please i appreciate u and send
me examples on mix design calculation & proportion!!!
thank u!!!!!!

hiten says:

what is W/C ratio for M15, M20, M30 & M35. Also tell me their cement content as per IS 456:2000.
Please do the needful for me. I want ans as soon as possible.
Thank u for your cooperation.

N.B.Doddamani says:

pl.give how to conduct Bend, Rebend tests for steel.

Alex says:

Dear Sir;
I am a QA/QC or Quality Engineer trainee sir, can u give me a proper checlist of pre and post concreting sir?with explanations sir so i can easily understand the checklist. thank you

Pooranachandran says:

Dear Sir,

Please tell me,Why we have provide Steel in the RCC works?

Pooranachandran says:

Dear Sir,

what are the relations between Post Stressed concrete and Pre Stressed concrete, Give the curing period the same.

allan says:


how can i compute for the design mix components for a concrete paver/paving block having a size of L=200mm x H=60mm x W=100mm and a compressive strength of 3000psi @ 28days…mixture is composed of cement, fine sand, coarse sand (black sand) & gravel 3-8″…thanks.

HBL says:

also interested for an answer to this question.

Thank you. Have been reading your posts all afternoon. Very helpful!

Sabarish says:

Dear Sir,

Can you please suggest me the percentage of addition of nano silica in concrete to attain higher strength.

Final year civil enggineering,
coimbatore Institute of technology,

D.R.Shetty says:

dear sir,

what is nanosilica……….
Sir can you please tell me briefly about water/cementitous ratio…..
Range of w/c ration



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