**Compressive strength of concrete** is one of the most crucial properties of concrete. It is the ability of concrete structures and surfaces to withstand the pressure of heavy loads. Higher compressive strength means there is higher resistance to stress and better ability to bear heavy weight.

Besides compressive strength, the other important factors to choose the right concrete mix are workability, flexibility, and overall durability.

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Construction experts recommend consulting a professional to select the best-suited concrete admixtures for the specific construction project as it is a complex process. However, if you have the basic knowledge of what compressive strength is, then you can also choose the right concrete superplasticizer admixtures according to your construction requirements.

In this blog, we will go in-depth into the definition of compressive strength of concrete, and how it is advantageous for construction purposes.

## What is the Importance of Compressive Strength of Concrete?

A compressive strength test gauges the resilience of hardened concrete by analyzing the concrete’s ability to bear loads that may compress it.

There are various reasons to test concrete’s compressive strength. A major reason is that concrete is a significantly strong material, but improper construction practices and unsuitable or low-grade construction materials can cause it to develop cracks and other types of physical damage.

Besides this, concrete is mostly used in high stress bearing structures such as buildings and bridges. Using concrete with low compressive strength poses the risk of making the structure deteriorate and causing it to collapse with frequent use.

When making concrete structures there are a variety of factors that need to be considered, but compressive strength is the most important. Testing is the best way to find out if the concrete admixtures is strong enough for the intended purpose.

## How to Measure Compressive Strength of Concrete?

Thanks to advances in construction science and technology, it is possible to measure concrete’s compressive strength using one of several different methods.

The usual way of testing the compressive strength of concrete is by making cylinders of a specific size and weight. These are then tested to gauge the ability of the concrete mix to withstand heavy loads.

A compression testing device is also used for this. The concrete cylinders are placed within the device and increasing pressure is applied on them.

Compressive strength is determined by dividing the cross-sectional area of the concrete cylinder with the greatest load it can bear before cracking or getting damaged.

There are several factors that are combined to determine the overall compressive strength of any concrete mix, such as the amount of aggregate, water-to-cement ratio, curing conditions, and the types of aggregates being used.

Ideally, the concrete’s compressive strength in industrial and commercial projects should be between 2200 psi (15 MPa) and 4400 psi (30 MPa), or above.

In simple words –

*Compressive Strength = Load / Cross-sectional Area*

Finding the compressive strength helps you to evaluate if the concrete mix is strong enough for the intended purposes. It is also useful to compare the strength of different concrete mixes. Besides this, finding compressive strength also helps to determine the durability of the concrete structure.

Apart from this, there are other ways to measure concrete’s compressive strength, such as –

### Rebound Hammer

A Rebound Hammer, also called the Schmidt Hammer, is a handheld device. It contains a small hammer head which is activated by a spring release mechanism. It strikes a plunger through the concrete surface.

The rebound distance between the concrete surface and the hammer is measured in values between 10 and 100. The results of this test help to determine the average compressive strength of surfaces made with concrete.

To get the most accurate measurement of compressive strength, you will need to pre-calibrate the device with cored samples. The measurement indicates the concrete’s compressive strength.

### Ultrasonic Pulse Velocity

The ultrasonic pulse velocity test measures the speed of vibration energy pulse across a concrete slab. The resistance faced by the ultrasonic pulse while traveling across the slab helps measure the stress (resistance to deformation), elasticity and density of the concrete. This data is then used to calculate the strength of the concrete.

This is a non-invasive and non-destructive method of calculating the compressive strength of the concrete. It can also successfully identify weaknesses in the concrete, such as honeycombing and cracks.

### Penetration Resistance Test

Penetration resistance test is an invasive testing method. The device used in this test inserts a small probe or pin into the concrete surface. The device measures the force it requires to push the probe into the concrete surface and the depth of the hole it creates to calculate the concrete’s compressive strength.

### Drilled Core

The drilled core test is another penetrative testing method for compressive strength. This method requires covering the pouring area with cylinder molds. These moulds remain in the slab and are filled with fresh concrete. Once the concrete hardens, it is removed and squeezed to measure strength.

However, this testing method requires compromising the concrete slab’s stability and the holes need to be fixed during the finishing stage.

### Pullout Test

The pullout test requires pulling the concrete with a metal rod which is inserted or cast into the concrete surface before it is laid. The force needed to withdraw the metal rod and the amount of concrete it pulls out is used to calculate the concrete’s compressive strength.

Though this testing method can be used to determine the compressive strength of old and new concrete structures, it causes noticeable damage to the concrete surface. You will need to draw out multiple concrete samples to get accurate results with the pullout test.

**Wireless Maturity Sensor**

The wireless maturity sensor method works on the theory that the temperature history of the concrete’s hydration determines the strength and quality of concrete. This test requires mounting the wireless sensors on the rebar before it is inserted into the concrete mold and the concrete is poured.

The wireless sensors measure the inner temperature of the concrete slab and send the information to an app on a smartphone. Using the maturity equation calculator, the compressive strength of the concrete is measured based on the temperature data collected by the sensors.

### Cast-in-Place Cylinders

The cast-in-place cylinders method is another penetrative test. It involves drilling a sample of the concrete upon hardening using a core drill. These samples are then compacted in a machine to simulate stress.

## What are the Factors that Affect Compressive Strength of Concrete?

There are several factors that affect concrete’s compressive strength. These include the kind of aggregate used, curing conditions, age of the concrete, the raw materials, and the water-to-cement ratio. All these factors have a direct influence on concrete’s compressive strength.

According to construction experts, the most important factor that determines concrete’s compressive strength are the raw materials used to make it. For optimal strength it is recommended to use the best quality cement, well-graded aggregates, that are free of impurities.

Apart from this the age of concrete is also a major factor in its compressive strength. Curing conditions are also important to ensure strong concrete slabs and surfaces. Hence, it is recommended to buy construction chemicals from renowned and trusted manufacturers, such as **Sakshi Chem Sciences Pvt Ltd**.

## How to Improve the Compressive Strength of Concrete?

There are several ways to improve concrete’s compressive strength. The simplest way to enhance the compressive strength is to increase the volume of cement in the concrete admixtures. This allows the concrete to bear heavier loads.

You can also add reinforced steel to the concrete which also increases the structure’s compressive strength.

Apart from this, you can choose a denser aggregate to enhance the concrete structure’s compressive strength.

**Conclusion**

Compressive strength of concrete is one of the main factors that help to determine the best kind of concrete to use for any construction project.

There are several methods to measure the ability of concrete structures and surfaces to bear heavy loads for long periods of time. These tests are useful to determine the best-suited concrete mix to use, and crucial to ensure strong and stable concrete structures.