A simple formula tells you the water consumption of concrete admixtures

Concrete mix ratio:

①Cement ②Coarse aggregate ③Fine aggregate ④Additives

Calculation method: Ordinary concrete mix ratio calculation book

Basic "Common Concrete Mix Proportion Design Regulations" (JGJ55-2000) (J64-2000) and "Building Construction Calculation Manual".

1. Calculation of concrete preparation strength

Concrete preparation strength should be calculated according to the following formula:

fcu, 0≥fcu, k+1.645σ

Where: σ——standard deviation of concrete strength (N/mm2). Take σ=5.00 (N/mm2);

fcu, 0——Concrete preparation strength (N/mm2);

fcu,k——Standard value of concrete cube compressive strength (N/mm2), take fcu, k=20 (N/mm2);

After calculation: fcu, 0=20+1.645×5.00=28.23 (N/mm2).

2. Calculation of water-cement ratio

The water-cement ratio of concrete is calculated according to the following formula:

Among them:

σa, σb—— Regression coefficient, since the coarse aggregate is gravel, look up the table according to the regulations and take σa=0.46, take σb=0.07;

fce——the measured value of cement 28d compressive strength, take 48.00 (N/mm2) ;

After calculation: W/C=0.46×48.00/(28.23+0.46×0.07×48.00)=0.74.

3. Calculation of water consumption

The determination of water consumption per cubic meter of concrete should comply with the following regulations:

1. Determination of water consumption for dry-hard and flexible concrete:

1) When the water-cement ratio is in the range of 0.40 to 0.80, the amount of water required for dry-hard and flexible concrete shall be determined based on the type of coarse aggregate, particle size and consistency of the concrete mixture required for construction. The water consumption is selected from the following two tables:

2) The water consumption of concrete with a water-cement ratio less than 0.40 and concrete using special molding processes should be determined through tests.

2. The water consumption of fluid and highly fluid concrete should be calculated according to the following steps:

1) Based on the water consumption of 90mm slump in the above table, the water consumption increases for every 20mm increase in slump. 5kg, calculate the water consumption of concrete without admixtures;

2) The water consumption of concrete with admixtures can be calculated according to the following formula:

Among them: mwa—— Water consumption per cubic meter of concrete mixed with admixtures (kg);

mw0——Water consumption of concrete without admixtures (kg);

β——Admixtures The water reduction rate is β=500%.

3) The water reduction rate of admixtures should be determined through testing.

The calculated water-cement ratio of concrete mwa=0.57×(1-500)=0.703

Since the calculated water-cement ratio of concrete=0.57, the water consumption is taken as the value in the table=195kg .

IV. Calculation of cement dosage

The cement dosage per cubic meter of concrete can be calculated according to the following formula:

After calculation, mco=185.25/0.703=263.51 kg.

5. Calculation of the amount of coarse aggregate and fine aggregate

The reasonable sand rate is determined according to the following table:

According to the water-cement ratio of 0.703, the coarse The type of aggregate is: gravel, coarse aggregate particle size: 20 (mm), check the table above, take the reasonable sand rate βs=34.5%;

Determination of the amount of coarse aggregate and fine aggregate, Calculated using the volume method, the calculation formula is as follows:

Among them: mgo——the benchmark coarse aggregate dosage per cubic meter of concrete (kg);

mso——the amount of coarse aggregate per cubic meter of concrete Benchmark fine aggregate dosage (kg);

ρc - cement density (kg/m3), take 3100.00 (kg/m3);

ρg - table of coarse aggregate Apparent density (kg/m3), take 2700.00 (kg/m3);

ρs——apparent density of fine aggregate (kg/m3), take 2700.00 (kg/m3);

ρw——water density (kg/m3), take 1000 (kg/m3);

α——percentage of air content in concrete, take α=1.00;

The above two equations are combined, and the solution is mgo=1290.38 (kg), mso=679.67 (kg).

The basic mix ratio of concrete is: cement: sand: gravel: water = 264: 680: 1290: 185

Or the weight ratio is: cement: sand: gravel: water = 1.00 :2.58:4.9:0.7.

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