Concrete testing

One of the most popular building materials in the world is concrete. Because of its strength, resilience, and adaptability, it is a crucial part of many different kinds of structures, including roads, bridges, and buildings. But it’s essential to test concrete thoroughly to make sure it works as planned. Concrete testing ensures that the material satisfies all requirements and standards while also assisting in the identification of any possible problems.

Concrete can be tested using a variety of techniques, each with a distinct function. These tests can be carried out on concrete that has just hardened, concrete that is still fresh, or even the raw materials for concrete. By being aware of these various tests and their significance, you can make sure that your concrete projects are durable and successful.

Common tests include the compressive strength test, which assesses the hardened concrete’s capacity to support loads, and the slump test, which gauges the consistency of fresh concrete. Additional tests could evaluate how well the concrete resists freezing and thawing cycles, how well it resists water penetration, or how much air it contains.

An essential first step in any building project is concrete testing. Through the implementation of these tests, engineers and builders can guarantee the consistency and quality of the concrete utilized, resulting in structures that are more robust and safe. Concrete testing can have a big impact on the result of any project, no matter how big or small. This is true for both residential and commercial developments.

Methods for testing concrete

Both hardened and unhardened concrete are tested before being used as a building material. The tests have different goals in this instance. The first scenario determines the solid material’s strength and other performance attributes, while the second scenario determines its technological indicators, such as workability, compactibility, plasticity, and air presence.

There are also destructive and non-destructive testing techniques. Let’s look at the different kinds of concrete mortar tests based on the "course" of application: tests conducted both before and after the material sets and gains grade strength.

Concrete testing GOST 10181.1-81

Concrete plant laboratories promptly prepare the commercial solution and then conduct concrete performance testing in compliance with this regulatory document’s requirements.

• Cone draft. Using this method, the heterogeneity and consistency of the material is determined. These indicators affect the workability of concrete. The essence of the method is to fill a metal cone with the concrete being tested, measure linear indicators after removing the shell (cone) and compare changes in the dimensions of the resulting “concrete paste” with tabulated values.
• Compaction test. This method allows you to set the compaction coefficient of a specific batch of building material. To determine this characteristic, the following technological equipment is used for testing concrete – an apparatus consisting of two measuring containers with funnels. The substance being tested is poured into the first funnel. The funnel has a valve through which the solution flows into a second funnel in a container of a smaller volume. Then the tested material falls into a special cylindrical form. The density and compaction coefficient of the solution in the cylindrical form are calculated mathematically.
• Test for plasticity and shape change. In this case, the tested material is poured into a test cone of certain dimensions, which is installed on a special support table. The table has the ability to move down a few centimeters when shaken. Then the form is carefully removed, and the table is lowered. The concrete spreads over its surface. Having carried out linear measurements of the average diameter of the "spread" form of concrete, the plasticity indicators of the tested material are determined.
• Checking for the presence of air voids in concrete mortar. Two methods are used. The first method is to measure the weight of the concrete sample before and after shaking with mixing in a pycnometer. Accordingly, to assess the presence of air in this way, very precise devices are used that can determine a slight deviation in mass. The second method is the pressure method. In this case, special air meters are used that show the content of air voids in the body of solid concrete.

The following quality control (testing) of concrete using the "empirical" method can be advised for private developers who are working with concrete for the first, and frequently the last, time in their lives:

• Color. High-quality concrete should have a gray-greenish color. In this case, the "greener" the delivered concrete, the better its quality. A yellow tint of concrete is a sign of its poor quality.
• So-called "cement milk" should appear on the surface of the laid concrete. The thicker this material, the higher the quality of the concrete.
• There should be no fractions of the filler uncovered by the cement and sand raster.
• After the concrete has completely hardened, the steel hammer should bounce off the surface with a ringing sound, leaving a shallow dent.

In order to guarantee the strength and longevity of concrete structures, concrete testing is essential. We can confirm that the concrete mix satisfies the required standards and specifications by conducting a variety of tests, including compressive strength, slump, and air content tests. This procedure contributes to the safety and durability of infrastructure and buildings by ensuring that possible problems are detected early on and that concrete performs well under a variety of circumstances.

Methods for testing hardened concrete

Compressive strength testing is the primary kind of concrete testing, and it is applied to all kinds of structures. This indicator’s significance is characterized by the concrete marking that it appears in.

There are two separate ways to determine strength. Prior to delivering the completed material to the job site, these laboratory tests check the strength of the concrete. At the construction site, they check the strength of a particular hardened material. In this instance, a concrete strength test report is created based on the test results for particularly significant structures. It includes the data gathered and the test date.

Let’s take a closer look at each approach. The current standard GOST 10180-2012 governs the requirements of the regulatory document, which governs the process for testing concrete for strength using laboratory methods. The method’s main step is to create cubic or cylindrical samples that are a specific size.

The GOST specifications also dictate the sizes of cubes used for concrete testing. These are concrete elements with edge lengths of 100, 150, 200, 250, and 300 millimeters. The diameter of cylindrical samples used for strength testing can be 100, 150, 200, 250, or 300 millimeters.

Using a social press, the samples are destroyed after being poured and held for a predetermined amount of time. Here, the destructive force—a mathematical value that describes the compressive strength of concrete—is noted. Although this approach is highly accurate, it isn’t always suitable.

Building cannot wait for concrete samples to solidify and acquire strength in their brand. As a result, in their practice, construction companies test the strength of concrete using empirical methods. The two primary categories of these techniques are partially destructive concrete and non-destructive concrete.

The most dependable approach is partial destruction technology, which regulatory documents mandate be used when commissioning a building. A unique steel disk is adhered to the surface of the tested structure using adhesive technology, which forms the technical basis of partial destruction technology.

The disk is then torn off along with a piece of concrete using a specialized tool. This concrete structure’s strength value is determined by measuring the amount of tearing force using a specialized device.

Determination of strength without destruction of concrete

Concrete ultrasonic testing is regarded as the most widely used non-destructive method for determining the strength value. The technique is based on altering the ultrasonic waves’ rate of passage through the material’s thickness.

Contemporary ultrasonic concrete testing instruments are "indicating," meaning that during testing they show the strength indicator in the necessary units. The "ultrasonic" technology’s primary drawback is a sizable measurement error.

• Testing concrete for tension and bending. The testing technology is similar to the technology for testing concrete samples for strength. The main difference between testing for tension and bending is the vector of application of the destructive load. When testing for strength, samples are "pressed" by a vertical load, and when testing for tension and bending, they are destroyed by a horizontal and "cantilever" force.
• Testing concrete for frost resistance. Frost resistance of concrete is measured in the number of "freeze-thaw" cycles that the structure can withstand before destruction. This value also refers to the main technical characteristics on which the durability of the structure depends. Frost resistance testing technology involves freezing and thawing control samples in laboratory conditions, after which a comparative analysis of the loss of strength and the corresponding determination of the frost resistance value is carried out.

Conclusion

The GOST proportions of concrete and cement-sand mortar components must be followed when building low-rise buildings and other structures privately. Additionally, buy cement from reliable vendors.

Concrete structures have a large margin of compressive, tensile, and frost resistance in low-rise construction, according to mathematical and practical computations of concrete strength.

To guarantee the strength, longevity, and general quality of concrete used in construction projects, concrete testing is necessary. Frequent testing aids in the early detection of any problems, enabling corrections and advancements prior to the emergence of significant issues.

Engineers and contractors can decide whether a concrete mix is appropriate for a given application by knowing the different testing techniques, such as permeability, compression, and slump tests. Every test offers insightful information about various facets of concrete performance.

Concrete testing ensures that your construction process complies with industry standards and improves the durability and safety of the structures you build. By taking the time to test and validate your concrete, you can be sure that your projects will meet the highest standards of quality, giving everyone involved peace of mind.

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