# Estimating Cement, Sand and Gravel Quantity for your Concrete Mix

Proportioning concrete mixture can be done by either weight or volume method. The volume method, which uses bags of cement and a measuring box as a reference for sand and gravel, has long been practiced by almost all types of concrete construction. However, in larger and bigger scale projects and in sites where mixing and material storage is not possible, ready-mixed concrete is used.

#### HOW TO ESTIMATE THE QUANTITY OF CEMENT, SAND AND GRAVEL FOR YOUR CONCRETE MIX:

1. Determine the volume of concrete you will need.

2. Determine your concrete mix class.

3. Your concrete’s compressive strength depends on your material’s mixture and proportions. You should select your concrete mix class according to where you will use the concrete. Here’s a basic table for the concrete mixture class with their corresponding use and application. 4. Determine your Portland cement bag quantity.

5. Local hardware stores have commercially-available Portland cement bags in two variants: 40kg and 50kg quantities. The number of cement bags you will need per mix will depend on the variant you’ve chosen.

6. Based on your concrete mix class and cement bag quantity, multiply your volume with the corresponding values from the concrete proportion table:

7. #### SAMPLE PROBLEM 1

Compute for the quantity of 40kg cement bags, sand and gravel needed for a class “A” mixture slab that is 3 meters long, 2 meters wide and 0.150 meters thick.

SOLUTION

1. Compute for the volume of concrete mix:

2. Volume = Length * Width * Height
V = 3m * 2m * 0.150m
V = 0.90m3

3. Determine the concrete mix class and Portland cement bags specified:

4. Specified concrete mix class = Class “A”

5. Determine the concrete mix class and Portland cement bags specified:

6. Specified Portland cement bag = 40kg

7. Match and compute for the quantity of sand, gravel and cement according to the concrete proportion table:

8. Quantity of 40 kg Cement Bags = Volume * Cement multiplier for a Class "A" in 40kg bags
= 0.90m3 * 9
= 8.1 bags

Quantity of Sand = Volume * Sand multiplier for a Class “A” mix
= 0.90m3 * .5
= 0.45m3

Quantity of Gravel = Volume * Gravel multiplier for a Class “A” mix
= 0.90m3 * 1
= 0.90m3

#### SAMPLE PROBLEM 2

Compute for the quantity of 50kg cement bags, sand and gravel needed for a class “C” mixture slab that is 5 meters long, 10 meters wide and 0.250 meters thick.

SOLUTION

1. Compute for the volume of concrete mix:

2. Volume = Length * Width * Height
V = 5m * 10m * 0.250m
V = 12.5m3

3. Determine the concrete mix class and Portland cement bags specified:

4. Specified concrete mix class = Class “C”

5. Determine the concrete mix class and Portland cement bags specified:

6. Specified Portland cement bag = 50kg

7. Match and compute for the quantity of sand, gravel and cement according to the concrete proportion table:

8. Quantity of 50 kg Cement Bags = Volume * Cement multiplier for a Class "C" in 50kg bags
= 12.5m3 * 5
= 62.5 bags

Quantity of Sand = Volume * Sand multiplier for a Class “C” mix
= 12.5m3 * .5
= 6.25m3

Quantity of Gravel = Volume * Gravel multiplier for a Class “C” mix
= 12.5mm3 * 1
= 12.5mm3

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