Concrete plays an important part in constructing both residential and commercial buildings. It is the basic layer that adds strength to the structure and binds it together. The stronger and more durable the concrete is the better. However, its strength can be compromised due to mixing and the use of impure cement which is why it is important to ensure the quality of the concrete being applied. This helps to mitigate any structural weaknesses in the buildings being constructed. Factors like the quality of the concrete, time used to set it and the way it is applied will determine the strength of concrete.
Contractors use different methods to measure a concrete’s strength. When choosing a method to calculate the strength of concrete the project manager considers the impact each technique will have on the project’s schedule. Some testing methods can be done directly on the site while some require extra time and some help from professionals to get the work done.
In this blog post, we will discuss 4 methods that are used to measure the strength of concrete.
Rebound Hammer Test
In this method, a spring release mechanism is used to activate a hammer which then impacts the plunger into the surface of the concrete. The rebound distance between the hammer and the surface of the concrete is the value that determines the strength of the concrete. This method is relatively easy to use than other methods and can be used onsite. But one con is that you will need pre-calibrated samples to get accurate measurements, and if there is any rebar below the surface it can also affect the results of this method.
Pull Out Test
In this test, the main principle is to pull the concrete using a metal rod that is cast-in-place or is post-installed on the concretes’ surface. In this method, a small piece of equipment is attached to an exterior bolt. Then this element is pulled out with extreme strength to determine the stress load level of the concrete. The cons of this method are that it can damage or crush the concrete and a large number of samples at different locations of the slab are needed for accurate results. However, this method is easy to use and can be used on both old and new construction sites.
Drilled Core Test
The drilled core test is one of the highly effective methods of concrete testing. In this method, hardened concrete is extracted from the slab by a core drill. Then the extracted samples are compressed in a machine to measure the strength of the concretes’ surface. The pros of this method are that the samples are considered more accurate than other methods as the concrete that is being tested has been subjected to the curing condition and actual thermal history. However, this is a destructive method as it involves the concrete slab being extracted from the actual surface which damages the integrity of the concretes’ surface. The cores and location will need to be fixed afterward and you will also need a lab to obtain the results.
Cast In-place Cylinder Test
As the name suggests this method uses cylinder molds that are cast into the concretes’ surface. These cylinder molds are placed in the location and then fresh concrete is poured into these molds which remain in the slab of concrete. Once the molds are hardened they are removed from the slab and are then compressed to measure the strength of the concrete. This method is considered to be more accurate than the field-curing method. However, this is a destructive method as it damages the integrity of the concretes’ surface. Also, you will need to repair the mold holes afterward, and you will also need to get a lab test done to obtain the strength data.
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