Formula for Determining the Compressive Strength of Concrete Cylinders- A Comprehensive Guide

How to Calculate Compressive Strength of Concrete Cylinder Formula: A Comprehensive Guide

The compressive strength of concrete is a crucial parameter that determines the structural integrity and durability of concrete structures. It is essential to calculate the compressive strength accurately to ensure the safety and reliability of buildings, bridges, and other infrastructure. This article aims to provide a comprehensive guide on how to calculate the compressive strength of concrete using the cylinder formula.

Understanding the Compressive Strength of Concrete

Compressive strength refers to the maximum load that a concrete sample can withstand before it fails under compression. It is typically measured in megapascals (MPa) or pounds per square inch (psi). The compressive strength of concrete is influenced by various factors, including the mix design, curing conditions, and age of the concrete.

Materials Required for Compressive Strength Test

To calculate the compressive strength of concrete using the cylinder formula, you will need the following materials:

1. Concrete cylinders: These are standard cylindrical specimens with a diameter of 150 mm and a height of 300 mm.
2. Compression testing machine: This machine applies a compressive load to the concrete cylinder until it fails.
3. Weighing scale: To measure the initial weight of the concrete cylinder.
4. Water and curing tank: To maintain the required curing conditions for the concrete cylinders.

Preparation of Concrete Cylinders

To calculate the compressive strength of concrete, you must first prepare the concrete cylinders. Here are the steps involved:

1. Mix the concrete according to the desired mix design.
2. Pour the concrete into the molds and compact it using a tamping rod.
3. Remove the excess concrete from the top of the molds.
4. Place the molds in a curing tank or room with a temperature of 20°C ± 2°C and a relative humidity of 95% ± 5%.
5. Allow the concrete to cure for 28 days before testing.

How to Calculate Compressive Strength of Concrete Cylinder Formula

The compressive strength of concrete can be calculated using the following formula:

Compressive Strength (f’c) = (Maximum Load (P) / Cross-sectional Area (A)) 1000

Here, the maximum load (P) is the force applied to the concrete cylinder at the moment of failure, and the cross-sectional area (A) is the area of the concrete cylinder at the point of failure.

To determine the maximum load, you can use the following steps:

1. Place the concrete cylinder in the compression testing machine.
2. Apply a compressive load at a rate of 0.5 MPa/s.
3. Record the load at the moment of failure.

To calculate the cross-sectional area, use the following formula:

Cross-sectional Area (A) = π (Diameter (D) / 2)^2

Where π is the mathematical constant (approximately 3.14159), and Diameter (D) is the diameter of the concrete cylinder.

Conclusion

Calculating the compressive strength of concrete using the cylinder formula is an essential step in ensuring the structural integrity of concrete structures. By following the steps outlined in this article, you can accurately determine the compressive strength of concrete and make informed decisions regarding the design and construction of your projects.