Everything You Need to Know About The Compressive Strength of Concrete

Compressive Strength of Concrete Definition

The compressive strength of concrete is measured by its ability to withstand compressive loads without failing. It indicates how well the material can resist pressure and maintain its integrity under stress.

While you can change many things in your home, the choice of cement and concrete is something you can’t compromise on. The strength of your home depends on the quality of materials used, and the right choice of cement ensures your concrete can deliver the strength and durability your home needs for years to come.

Importance of Strength Test of Concrete

Strength tests are essential for determining whether the concrete mix prepared on-site meets the specifications of your project. These tests provide insights into key parameters like: 

1. Strength

2. Consistency

3. Unit Weight

4. Air Content

5. Temperature

As your home is your identity, make decisions that reflect its importance. The right concrete mix ensures the strength and resilience that will last for generations.

Concrete Strength Testing Methods

There are many other methods and tests to check the compressive strength of concrete. Let’s take a look at a few of these approaches:

1) Rebound Hammer or Schmidt Hammer

In this method, a hammer is activated by a spring release mechanism, striking a plunger to drive through the concrete's surface. A value between 10 and 100 is assigned to the rebound distance between the hammer and the concrete surface. The strength of the concrete is then associated with this measurement. 

This method of checking the compressive strength of concrete is relatively easy to use. However, pre-calibration using cored samples is needed for accurate results. Moreover, although this can be done directly on-site and helps save time, the results can be led astray by surface conditions or other factors.

2) Penetration Resistance Test

To complete a penetration resistance test, a small pin or probe is driven into the surface of the concrete through a device. The strength of the in-place concrete is linked with the force required to pierce the surface and the depth of the hole.

This method of checking the compressive strength of concrete,  also requires pre-calibration using several concrete samples to provide accurate results. Although it is easily carried out on-site, the measurements are affected by surface conditions and forms of aggregates used.

3) Ultrasonic Pulse Velocity

This method calculates the speed of a vibrational energy pulse across a slab. The ease with which this energy passes through the slab yields data on the concrete's density, elasticity, and resistance to deformation or stress. This data is then used to determine the slab's strength.

The technique is non-destructive and can identify faults like cracks and honeycombing in the concrete. However, the results are majorly influenced by reinforcements, aggregates, and moisture content of the concrete component and require pre-calibration using several samples.

4) Pullout Test

The fundamental idea behind this test is to pull the concrete using a metal rod that has been inserted or cast in place. The compressive strength of concrete is associated with the pulled conical form and the force needed to draw out the concrete.

While this method can be effectively carried out on old and new construction sites alike, it involves destroying the concrete. The compressive strength test of concrete also requires extensive samples to provide exact results.

5) Drilled Core

In this method, the pouring area is covered with cylinder moulds. The moulds, which remain in the slab, are filled with fresh concrete. Once solidified, the specimens are removed and squeezed for strength.

Because the concrete is treated to the same curing circumstances as the in-place slab, as opposed to field-cured specimens, it is considered more accurate. However, this kind of construction compromises the slab's structural stability and the data must be obtained in a lab. After that, the holes must be fixed where they were.

6) Cast-in-place Cylinders

In this method, hardened concrete is removed from the slab using a core drill. Subsequently, these samples are compacted in a machine to measure the strength of the in-situ concrete.

Because the concrete that is tested for strength has been exposed to the same thermal history and curing circumstances of the in-place slab, these samples are considered more precise than field-cured models. However, this method of checking the compressive strength of concrete is also destructive and requires a lab for data measurement. 

7) Wireless Maturity Sensors

This method is based on the notion that the temperature history of the concrete's hydration is closely related to the quality and strength of the concrete. Before pouring, wireless sensors are mounted on the rebar and inserted into the concrete formwork. 

The sensor gathers temperature information, which is wirelessly transferred to any smart device and stored in an app. Based on this data and the maturity equation set up in the app, the compressive strength of the concrete is calculated.

The Calculation for the Compressive Strength Test of Concrete

Calculating the compressive strength of concrete involves determining the force required to break a concrete cylinder. This value is key to understanding the material’s ability to withstand pressure. Engineers rely on these calculations to ensure every structure meets safety standards.

When building your home, it's crucial to get the foundation right the first time. The compressive strength test ensures your home’s structure can withstand the test of time and pressure.

Also read: Grade Of Cement