Concrete Mix Proportions: Determining Quantities of Cement, Sand, and Aggregate for a 250 Cubic Foot Slab

In this article, we will discuss the process of determining the quantities of cement, sand, and coarse aggregate required for a concrete slab with a volume of 250 cubic feet. The mix ratio used is 1:4:7, representing the proportions of cement, sand, and coarse aggregate, respectively. We will step through the calculations to ensure you have the correct quantities for your project.

Step-by-Step Guide to Calculating the Quantities

Step 1: Determine Total Parts of the Mix Step 2: Calculate the Volume of Concrete Required Step 3: Calculate Quantities of Cement, Sand, and Coarse Aggregate

Step 1: Determine Total Parts of the Mix

Given a mix ratio of 1:4:7, the total parts of the mix are calculated as follows:

1 4 7 12 parts

Step 2: Calculate the Volume of Concrete Required

The total volume of concrete is 250 cubic feet, and the thickness of the slab is specified as 6 inches. First, we convert the thickness from inches to feet:

Depth 6 inches / 12 0.5 feet

Next, we need to ensure that the total volume of 250 cubic feet correctly accounts for the slab’s dimensions. Assuming an area of the slab (A) in square feet, we can calculate the volume of the slab:

Volume of slab A × Depth

To find the area (A), we use the total volume of the concrete:

A Total Volume / Depth 250 ft3 / 0.5 ft 500 ft2

Step 3: Calculate Quantities of Cement, Sand, and Coarse Aggregate

Using the volume of the concrete (250 cubic feet), we now calculate the volume of each component based on the total volume:

Cement Volume

Cement Volume (1 / 12) × 250 ft3 20.83 ft3

Sand Volume

Sand Volume (4 / 12) × 250 ft3 83.33 ft3

Coarse Aggregate Volume

Coarse Aggregate Volume (7 / 12) × 250 ft3 145.83 ft3

Summary of Quantities

Cement: Approximately 20.83 cubic feet Sand: Approximately 83.33 cubic feet Coarse Aggregate: Approximately 145.83 cubic feet

The calculations provided here will help you determine the exact quantities needed for your slab concreting project. If you have other mix ratios or different sizes for your project, you can follow the same steps to find the necessary quantities of ingredients.

Additional Calculations

For further verification, let's perform the additional calculations provided in the summary:

Cement

Cement Volume (1.541 / 12) cubic feet 0.128 cubic feet

Converting to bags:

0.128 cubic feet × 1440 kg/cubic feet 184.8 kg

184.8 kg / 50 kg/bag 3.69 bags

Equivalent in cubic feet:

3.69 bags × 1.226 cubic feet/bag 4.53 cubic feet

Sand

Sand Volume (1.544 / 12) cubic feet × 35.3147 18.13 cubic feet for 10 cubic feet

For 250 cubic feet:

18.13 cubic feet / 10 cubic feet 181.3 cubic feet

Aggregate

Aggregate Volume (1.547 / 12) cubic feet × 35.3147 31.73 cubic feet for 1 cubic foot

For 250 cubic feet:

31.73 cubic feet / 1 cubic foot 7932.5 cubic feet

These additional calculations provide further validation for the quantities needed for the concrete mix.