Concrete Strength Testing Methods You Should Be Aware Of

For project managers to make an informed decision about which method to use for concrete strength testing and monitoring, it is critical to evaluate each approach’s effect on their timeline. 

Many tests are needed on-site, while some procedures call on third-party facilities to provide strength data, which adds time to the overall testing process. Project managers make choices based on a variety of factors, not only time constraints. 

Precision in the testing procedure is equally essential since it directly impacts the quality of the concrete building.

Samples are cast and cured following ASTM C31 specifications, and a third-party lab evaluates their compressive strength at different phases of the process. Typically, after the slab has achieved 75 percent of its intended strength, engineers will give their team the green light to proceed to the next stage of the building process.

The curing process has seen many advancements since professionals originally established this testing technique, many of which have resulted in faster curing times. This involves the use of heated blankets, additives, vapor retarders, and other similar measures. 

On the other hand, contractors continue to wait three days after their pour before testing for strength, even though their goals are to assess the methods made immediately.

The Tests That You Must Need

1. Rebound Hammer

The good side of this test is that it is very manageable to use and is completed on-site.

However, acquiring accurate measurements need pre-calibration using cored samples, which is not always possible. Surface conditions and the presence of big stones or rebar underneath the testing site may cause test findings distorted.

2. Penetrating Resistance Examination (ASTM C803)

The good thing about this test is that it is straightforward to use and may be completed on-site.

However, surface conditions and the kind of form and aggregates used have a significant impact on the data quality. Pre-calibration using several concrete samples requires testing also to get reliable strength readings.

3. Pulse Velocity of Ultrasonic Waves (ASTM C597)

This is test is a non-destructive examination method that contractors may use to identify defects in concrete, such as fractures and honeycombing, without causing damage to the concrete. The presence of reinforcements, aggregates, and moisture in the concrete element has a significant impact on the performance of this method. 

Additionally, for proper testing, it is necessary to calibrate with several samples.

4. Pullout Examination (ASTM C900)

This kind of examination is simple to utilize and made on both new and ancient structures alike.

The downside of this test is that it requires crushing or injuring the concrete. Many test samples taken from various places on the slab are needed to get reliable findings.

5. Cylinders cast in situ (ASTM C873)

The process is more accurate than field-cured specimens because, unlike field-cured examples, the concrete is exposed to the same curing conditions as the in-place slab, while field-cured samples are not. But this is a disruptive method that demands that the slab’s structural integrity be compromised. After that, contractors must fill up the holes in their original positions. It is necessary to utilize a laboratory to have the best results in the end.

6. Core that has been drilled (ASTM C42)

Because the concrete test laboratory uses strength exposed to the exact temperature history and curing circumstances of the in-place slab, these samples entail being more accurate than field-cured specimens. This is a disruptive method that demands that the slab’s structural integrity be compromised. Contractors must restore the core sites if they then dismissed the core.

Measurement of Concrete Strength Using a Combination of Methods

When it comes to quality control and quality assurance of a concrete structure, it is occasionally necessary to utilize a mix of these techniques for evaluating compressive strength. Using a combined approach provides a complete picture of your slab, enabling you to validate strength data by practicing more than one testing method to assess its overall strength. The accuracy of your strength data will also improve due to the use of various techniques, which will assist in accounting for affecting variables such as cement type, aggregate size, and curing conditions, among others.

Determine Which Method of Measuring Concrete Strength Will Be Used in Your Next Pour by Following These Steps.

While tests such as the rebound hammer and penetration resistance technique are simple to conduct, they are less accurate than other types of testing techniques (Science Direct). 

This is because they do not check the core of the concrete element but rather just the curing conditions immediately under the slab’s surface instead. 

Practicing techniques such as the ultrasonic pulse velocity method and the pullout test that require many sample specimens to obtain accurate data are more challenging to perform. This is because their calibration processes are time-consuming and need a large number of sample specimens. Because they are destructive testing procedures, the drilled core and cast-in-place cylinder methods rely on third-party laboratories to conduct some breaking tests to get data on their results. Consequently, while utilizing any of these techniques, you will need to allocate extra time to your project timeline. 

In comparison, the maturity approach provides real-time strength data that can be accessed on-site, enabling well-informed and timely decision-making. It is also possible to minimize the errors associated with testing laboratories by reducing your dependence on break tests and other similar methods.

Your choice of the testing technique to employ may simply rely on what you are familiar with and comfortable with and not in demand. However, the accuracy of these tests and the time it takes to collect strength data are important considerations that every stakeholder should be aware. Consider where all of your time and money spent throughout a project’s building phase and if the method is necessary to comply with the area’s rules and regulations.

The precision of the method you select may result in future problems with the longevity and performance of your concrete building. Further yet, choosing a process that requires more time to get strength data may be harmful to your project’s deadlines, as well as to the overall efficiency of your workforce on the worksite.