Concrete design and placement is so safe that we rarely think about concrete safety today.  Through advances in technology, the creation of standards, and the implementation of testing processes, the concept of concrete safety tends to remain outside of general conversation regarding concrete. The basic concrete testing methods developed apply to concrete regardless of the type from traditional concrete to shotcrete to lightweight concrete.

Why concrete testing is needed

There are a multitude of concrete varieties designed for specific applications. Each concrete type has a few basic structural characteristics, such as density and compressive strength, that are major factors in how the concrete will perform.  In general, concrete has a high compressive strength which makes it a great building material. The density of a concrete is important when considering the weight of the concrete being placed and how that interacts with the overall construction specifications. It is imperative that the structural characteristics of the concrete align with the design specifications. Concrete constituents and onsite factors can impact the compressive strength, such as the ratio of water to cement, the amount of aggregate and additives, and even the weather. To maintain construction site safety, the final concrete product requires that testing be completed during placement and while curing to ensure it will meet all requirements of compressive strength and density.

Concrete testing methods

Concrete can be tested when it is still plastic and being placed, but testing can also be performed nondestructively on hardened concrete using different techniques. Inspecting hardened concrete for cracks or inconsistencies in the material can be a non-destructive testing method. Typically, inspection is done with impact echos, ultrasound, as well as visual inspection. This method is suitable for existing concrete construction and helps to troubleshoot problems and understand its internal structure.

Concrete testing process

Years of testing and innovation have led to various concrete mixtures that have characteristics engineered for certain applications. For any given project, the concrete mixture is generally determined more than 30 days before any concrete is poured. The characteristics of the mixture and a sample are reviewed and validated by engineers using their design models of the project.  Each morning when a concrete batch is poured, a sample is extracted. Every few hours throughout the day, additional samples are taken. These samples are checked for density to ensure that the composition meets the predetermined specifications. Additionally, samples are taken from the job site in order to be tested later for compression strength. These tests are conducted usually 7 and 28 days later to observe if the compression strength of the concrete is increasing at the designed rate.