What Are The Various Tests Performed On Concrete?

By Author: National Labs
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Concrete is a composite substance made up of a binding medium and embedded aggregate particles or fragments, typically a combination of fine and coarse aggregates; in Portland-cement concrete, the binder is a Portland-cement and water mixture with or without admixtures.

Tests for Concrete Quality Check
In order to evaluate its quality, concrete must be subject to on-site unitary inspections.

As part of the quality control of concrete structures, tangible quality controls are conducted in Concrete Testing Lab or on-site. The quality of the concrete for a specified specification is ensured by the use of compressive resistance checks, slump tests, permeability tests, and other concrete consistency tests.

These concrete quality tests provide an insight into the characteristics of concrete-like strength, durability, air content, permeability, etc.

Project managers need to take into account the impact each technique has on the schedule when choosing a method for monitoring the compression strength of concrete. While some testing procedures may be performed on-site, others necessitate additional time ...
... to provide strong data to third-party facilities. Time is not the only factor contributing to the decisions of project managers. The consistency of the testing technique is critical since the efficiency of the concrete construction is directly affected.

The results of each concrete quality test decide the concrete’s overall quality. As a result, it is impossible to conduct all the tests in the construction materials testing laboratory needed to assess the consistency of concrete. We must choose the best tests that will enable us to make an accurate assessment of the concrete quality.

The primary consistency measure specifies whether the concrete specification varies from what is necessary and what is normal. The quality checks ensure that the highest-quality concrete is used on the job site, resulting in concrete structural members with the required strength.

Types of Quality Tests on Concrete
construction materials testing laboratory
Concrete testing is important for ensuring the strength and durability of constructed structures. Field testing and laboratory testing are the two most common types of concrete material testing.

Field Testing of Fresh Concrete

Concrete field testing may take place during the construction process or during investigative tests of already-installed concrete to assess its strength qualities through the team of a construction materials testing laboratory.

Concrete Slump Tests

Concrete slump testing is used to evaluate the flow properties of freshly mixed concrete. Slump tests are carried out by pouring concrete into an inverted cone in three stages and tamping down the concrete with a metal rod after each stage. Once the cone is full, it is raised off the working surface with handles on both sides, and the concrete subsides or “slumps” into the ground due to gravity. The slump is determined by calculating the difference between the initial and slumped heights.

The following are the reasons why slump tests are used in practice for concrete quality control testing:

● The slump test is used to assess the consistency of the blend. This research looks at the different types of building materials used in the mix. These tests are based on the concrete mix’s water-cement ratio.

● The slump test is simple to carry out. It quickly assesses the consistency of concrete prior to its placement. The criteria for placement are based on the recommendations of the respective concrete practice codes.

● Slump testing is done on-site and does not necessitate the use of a lab or costly testing equipment. As a result, this test is cost-effective.

● Before pouring into the formwork, we perform a slump inspection. As a result, if the concrete consistency is poor, the checked batch may be rejected. This will aid in the removal of a faulty structural member and the avoidance of possible demolition and repair.

Air Content Testing

Air is induced to expand and contract capabilities within the concrete, especially in areas where external temperatures have changed substantially. Field air content testing of concrete is conducted for determining whether the delivered concrete complies with the air content requirements of the engineer.

The field technician appointed by a construction materials testing laboratory performs an air content test by using a circular metal basis with three concrete lifts that are tampered with a rod similar to that used in the test of concrete slumps. After the base is full of concrete, a metal deck is placed on top with a pressurizer and the two components are locked together. The device is pressurized with a hand pump and can then be stabilized to a calibration point. The pressure is released the following stabilization and the technician can read the concrete air content in a dial on the device.

Unit Weight

The concrete’s unit weight is reasonably simple to calculate. Fresh concrete is poured into a known-volume container and measured to assess the concrete’s unit weight or density.

Field Testing of Existing Concrete

The strength of the existing concrete is often needed for forensic investigations and retrofits. Nondestructive and destructive methods are the two most common ways of determining strength.

Schmidt Rebound Hammer

A Schmidt Rebound Hammer is the prime instrument for nondestructive testing of the concrete. The hammer works by firing a spring-charged mass on the concrete and measuring the rebound value of the mass of the concrete. This value can be compared with a converting diagram in order to provide a rough assessment of concrete compressive strength. In order to establish an average value, the hammer should usually be measured before use, and the test applied at multiple points in the test area.

Destructive Concrete Testing

To achieve a much more accurate value for the concrete compressive strength, a destructive test can be performed. This process involves covering the existing concrete and removing a cylinder, which is then transported to a testing laboratory in the same manner as newly ship-fed concrete cylinders.

Lab Testing of Concrete

Destructive testing in a Concrete Testing Lab is the best way to assess compressive and flexural strength.

Compressive Strength Lab Test

Laboratory testing on representative cylinders of concrete from that project is performed to determine whether the concrete delivered and installed at a construction site meets the strength specifications set by the engineer. The cylinders are formed in the field during the concrete pouring process and are selected at random points during the process. Concrete is mounted in three lifts in plastic molds to make the tubes, each of which is compacted with a metal rod during placement. Until being picked up and shipped to a concrete testing laboratory, cylinders are normally allowed to cure in the field for a few days.

The concrete cylinders will be tested in the laboratory at 7, 14, 28, and sometimes 56 days after field installation to assess compressive strength. This is achieved with a system that applies force to the concrete cylinder’s ends until it splits under the load. To get strength in pounds per square inch, divide the value of the force at breakage by the cross-sectional area of the cylinder.

The following are the reasons why the compressive strength and slump tests are used in practice for concrete quality control testing:

The compressive strength, which is measured by a compressive strength test, is responsible for most concrete properties.
The compressive strength test is the simplest, most cost-effective, and most precisely determinable test.
Compressive strength checks are the best way to study the variability of concrete.
Tensile Testing of Concrete

One of the most fundamental and critical properties of concrete is its tensile strength, which has a significant impact on the degree and scale of cracking in structures. Furthermore, due to its porous nature, the concrete is very fragile under tension. As a result, it is unable to withstand direct tension. As a result, when tensile forces surpass the concrete’s tensile strength, cracks emerge. As a result, the tensile strength of concrete must be determined in order to determine the load at which the concrete members will crack.

The testing specimens are rendered in the form of a rectangular beam in a Concrete Testing Lab, which is loaded on both ends until it snaps in the center, providing engineers with a measure of the concrete’s bending power.

Permeability Tests on Concrete

Permeable concrete may cause corrosion in the presence of oxygen, humidity, CO2, SO3– and Cl–. The development of rust causes the volume of the steel oxide to approximately 6 times and leads to the cracking and splashing of reinforced concrete.

It works under vacuum and can be conducted both on-site and in the laboratory. A two-chamber vacuum cell and a pressure regulator maintain airflow at right angles to the surface and into the inner chamber, which are important features of the method of measurement.

The test should be conducted on a dry, crack-free surface. Inner chambers should not be located above the reinforcement bar, if possible.

Pressure loss is calibrated regularly and after a significant temperature or pressure transition.

The coefficient of permeability is determined by taking 3 to 6 measurements of the concrete’s electrical resistance and combining the results. This allows a theoretical model to be used to calculate the permeability coefficient kT.

The results for dry concrete match those of laboratory tests such as oxygen permeability, capillary suction, chloride penetration, and others. The electrical resistance of the concrete is used to compensate for humidity, which has a significant impact on permeability. The quality class is calculated using kT and a monogram.

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National Lab GmbH, headquartered in Mölln in Schleswig-Holstein, has been an independent, purely German company since it was founded in 1918. Due to the strong international orientation and the high level of recognition in scientific laboratories around the world, the English pronunciation of the company name has become common.