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This is very good question and the most important part in site supervision,there are different ratio's used in various cases in which we would opt for water cement ratio (.4 to .6) according to is456.the following table is given in is456.If we take50kg cement then water to be taken would be50X.4 litres in the case of water cement ratio .4.we usually take .4 as water cement ratio in sites unless specified or different grades.I hope the answer is to the question please contact me for further clarification
Sl No.
Exposure
Plain Concrete
Reinforced Concrete
Minimum Cement Content kg/m2
Maximum Free Water-Cement Ratio
Minimum Grade of Concrete
Minimum Cement Content kg/m2
Maximum Free Water-Cement Ratio
Minimum Grade of Concrete
1
(2)
(3)
(4)
(5)
(6)
(7)
(8)
i)
Mild
220
0.60
-
300
0.55
M20
ii)
Moderate
240
0.60
M15
300
0.50
M25
iii)
Severe
250
0.50
M20
320
0.45
M30
iv)
Very Severe
260
0.45
M20
340
0.45
M35
v)
Extreme
280
0.40
M25
360
0.40
M40
Your information is not wrong, but you must consider
what is your environment (weather (hot/cold temperature), If you use adjuvents, The %W in your aggregates, your method of using for the implementing (pump, or non), and know what is the type of construction. Genéraly it's the laboratory who build the formulation.
the50 kg bag cement is equivalent to35ltr
now water should be added40% to45% by volume
i.e. (40*35/100 or45*35/100) =14 to16 ltrs of water per cement bag
by knowing the no. of cement bags you can calculate the total volume of water required using this method
W/C (Water/Cement) Ratio Is Importanrt Factor To Obtaining The Volume Of Water.(Note:This Ratio Reversely Affects The Strength Of Concrete)
Ratio Equal To .2 Is Adequate For Intiating Of Cementation But Working With Concrete That Is Made Of This Ratio In Impossible Practically Becaase The Concrete Doesn't Have Workability.
According To International Codes Ratio Between .4-.45 Will Be Sufficient
Although by visual observation, it is easy to tell if a batch of concrete is wetter than other previous batch. This visual test needs to be checked by more reliable methods to ensure greater accuracy. Such methods include slump test and compacting factor apparatus.
to me Shefeek answer is more closer and simple to Quantity Takeoff purpose, for other design and QA QC purpose it need more detailed study then refereing to Stantards.
water cement ratio should be selected on basis of strength and workability requirements .Reproduced by permission of the American Concrete Institute from recomended practice for selecting proportions (A.C.I.613-54 )
When sulfate resisting cement is used ,maximum water cement ratio may be increased by0.5 gal per bag .
Quantity of water required for various mixes of Plain or Reinforced concrete can be taken between8 to20 % of weight of Cement (50Kg or P/Bag) in Gallons utilization of water may decrease or increase as per the envoirnment in which Conrete is prepared. Allowance for wastage can be taken10 to15% if Concrete being mixed at Site.
the quesion is not clear.
if it means during mix design of concrete;
then water quantity can be calculated based on free water cement ratio (DOE method)
.
can we tak5% of aggregats and33% of cement for all ordinary concrete??????
(15-20%) water ratio.
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