1. Mixing our Concrete

2. These are our ingredients.
Calculating the Mix
Material
Cement
Sand
Gravel
Water
These are our ingredients.

3. This is how much each ingredient weighs per ft3.
Calculating the Mix
Material
lb/ft3
Cement 94
Sand
110
Gravel
105
Water 47
This is how much each ingredient weighs per ft3.

4. Calculating the Mix Material lb/ft3 Proportion Cement 94 1 Sand 110 2
Gravel
105 3
Water 47
0.5
These are commonly used proportions for a regular concrete mix.

5. This is % of each ingredient in the mix.
Calculating the Mix
Material
lb/ft3
Proportion
% Mixture
Cement 94 1
15%
Sand
110 2
31%
Gravel
105 3
46%
Water 47
0.5 8%
This is % of each ingredient in the mix.
1P + 2P + 3P + .5P = 6.5P
100% = 15.38%
6.5P

6. Calculating the Mix Material lb/ft3 Proportion % Mixture Mix lb/ft3
Cement 94 1
15%
23.08
Sand
110 2
31%
46.15
Gravel
105 3
46%
69.23
Water 47
0.5 8%
11.54
1 ft3 of concrete weighs 150 lbs., so we can calculate the weight of each ingredient by multiplying it by the %.
150 lbs. x 15% = lb/ft3

7. Calculating the Mix Material lb/ft3 Proportion % Mixture Mix lb/ft3
Mix lb/yd3
Cement 94 1
15%
23.08
623.08
Sand
110 2
31%
46.15
Gravel
105 3
46%
69.23
Water 47
0.5 8%
11.54
311.54
1 yd3 of concrete is 27x the size of a ft3, so we can multiply by 27 to get the weight of each ingredient per yd3.
23.08 lb/ft3 x 27 = lb/yd3

8. Calculating the Mix Material lb/ft3 Proportion % Mixture Mix lb/ft3
Mix lb/yd3
lb/.27 yd3
Cement 94 1
15%
23.08
623.08
6.3
Sand
110 2
31%
46.15
12.6
Gravel
105 3
46%
69.23
18.9
Water 47
0.5 8%
11.54
311.54
3.2
We can figure out the volume of our form, and then multiply that by the weight of each ingredient to get the amount we need to put into our mix.
V = ½h(a+b) x L/12
144
= .5 x 3” x (9” + 11”) x 15.75”
= .27 yd3

9. Calculating the Mix Material lb/ft3 Proportion % Mixture Mix lb/ft3
Mix lb/yd3
lb/.27 yd3
Cement 94 1
15%
23.08
623.08
6.3
Sand
110 2
31%
46.15
12.6
Gravel
105 3
46%
69.23
18.9
Water 47
0.5 8%
11.54
311.54
3.2
Finally, we multiply the total amount of concrete in our form by the weight of each ft3 of ingredient to get the weight of each ingredient needed for our mix.
.27 yd3 x lb/ft3 = 6.3 lbs

10. Use these numbers to weigh each ingredient on the scale before mixing.
Calculating the Mix
Material
lb/ft3
Proportion
% Mixture
Mix lb/ft3
Mix lb/yd3
lb/.27 yd3
Cement 94 1
15%
23.08
623.08
6.3
Sand
110 2
31%
46.15
12.6
Gravel
105 3
46%
69.23
18.9
Water 47
0.5 8%
11.54
311.54
3.2
Use these numbers to weigh each ingredient on the scale before mixing.