Water / Cement Ratio Calculation
Water / Cement Ratio Calculation
(OP)
I am currently at issue with an existing equation used to calculate the weight of water in a concrete mix and ultimately the water/cement ratio.
Known:
Sand Wt: 13,270 lb's ---- 4.9% Moisture Content
Coarse Agg. Wt. 6,800 lb's ---- -0.5% Moisture Content
Wt. of H2O added at plant: 1,650.33 lb's
Wt. of H2O added onsite: 83.35 lb's
Cement Wt.: 4,945 lb's
Flyash Wt.: 1,240 lb's
This is the equation used to determine the free water in the sand. (is this correct?)
[(13,270 lb's)*(0.049)] / (1 + MC/100) = 619.86
.....
and the water/cement ratio we come up with is:
0.375
I know this is simple, but any and all input is appreciated.
Known:
Sand Wt: 13,270 lb's ---- 4.9% Moisture Content
Coarse Agg. Wt. 6,800 lb's ---- -0.5% Moisture Content
Wt. of H2O added at plant: 1,650.33 lb's
Wt. of H2O added onsite: 83.35 lb's
Cement Wt.: 4,945 lb's
Flyash Wt.: 1,240 lb's
This is the equation used to determine the free water in the sand. (is this correct?)
[(13,270 lb's)*(0.049)] / (1 + MC/100) = 619.86
.....
and the water/cement ratio we come up with is:
0.375
I know this is simple, but any and all input is appreciated.





RE: Water / Cement Ratio Calculation
RE: Water / Cement Ratio Calculation
RE: Water / Cement Ratio Calculation
RE: Water / Cement Ratio Calculation
Weigh the collected sample and record it prior to drying. Use a hot plate, microwave oven or some other means of drying. Note that very rapid heating may cause some particles to explode, resulting in the loss of particles, which may render your calculations inaccurate. The sample is considered dry when further heating would cause less than 0.1 percent additional loss in mass. Allow the sample to cool to avoid damaging the scale. Weigh the sample to the nearest 0.1 percent. Calculate the total aggregate moisture content (MC) using the follow equation:
MC = (Wi - Wod)/Wod * 100%
MC = Moisture Content
W initial = Weight of the sample prior to drying
W od = Weight of the sample after drying
By using the moisture content and absorption of the aggregates, you can adjust the batch weights to account for the actual moisture condition. If the moisture content is higher than the aggregate's absorption value, the aggregates will contribute free water to the mix. If the moisture content is below the absorption value, the aggregates will absorb a portion of the mix water.
Calculate the adjusted fine aggregate (FA bw) batch weights using the following equation for each material:
FAbw = 13270
FAbw = FAdw * (1 + MC/100) = 12650 * 1.049
Therefore, the MC of the sand would be:
FAbw - FAdw = 13270 - 12650 = 620
The water-to-cement ratio is the weight of water provided in a mix divided by the weight of cementitious materials. The total weight of water includes all batch water and free water from the surface of aggregates.
w/c ratio = (619.85 lb + 33.83 Lb + 1650 Lb + 83.35 Lb)/(4,945 lb's + 1,240 lb's)
w/c ratio = 2387.03/6185 = 0.3859
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RE: Water / Cement Ratio Calculation