Compression tests with concrete cylinders or cubes (break tests) and the Maturity Method are two approaches with the aim to gain knowledge about the current strength and maturity status of the concrete. However, they differ in their approach:
The most important differentiation is that break tests are an example of a destructive test method and the Maturity Method represents a non-destructive test based on measurements and calculations.
The strength development of a concrete structure is strongly influenced by its chosen ingredients, compounds and external curing circumstances as weather conditions. As a complex product, concrete testing is essential to ensure compliance with specifications and requirements. Contractors, architects, legal requirements and other parties involved in a construction project have different priorities, which makes this process a complex task.
HOW BREAK TESTING WORKS
The Tradition of using Break Tests
Break Tests, also called Compression Tests are the traditional and established way to test the current strength development of the concrete structure with a destructive approach. Test specimen, usually either concrete cubes or cylinders, are cast and left on-site assuming to cure under the same circumstances than the on-site concrete and reflecting the same strength development. Then, the test specimen are taken to a laboratory for a compression strength test to draw inferences to the on-site structure.
Thus break tests determine the strength of a concrete cylinder or cube cured under on-site conditions and are commonly applied in national standards or contract requirements. To comply with the strength requirements, the average of three successive test results must at least meet or exceed the stated strength and no test must go below a set percentage of the pre-defined strength.
Break Testing Standards
COMPRESSION TESTS WITH CONCRETE SPECIMEN
- One of the most commonly used method to estimate the compressive strength from a test specimen to on-site structure
- Internationally accepted testing standard
- Limited preparation needed
- Accuracy is limited as the test specimen do not reflect the same in-place strength variations within the same structure and do not reflect the internal temperature as the on-site structure.
- Post-hoc analysis
Chemical Processes and Concrete Maturity
Concrete Maturity and the Maturity Method is a chemical process which on the one hand creates heat and on the other hand is also highly influenced by its surrounding temperature. Concrete Maturity explains the ratio between concrete temperature and its strength development specific for each concrete mix. Thus, for each concrete recipe, the maturity index varies and a different maturity calibration curve applies.
The principle of concrete maturity is the basis for the maturity method, a non-destructive test procedure to determine the strength development. With continuously following the temperature directly in the structure, the effects of time and temperature are monitored. The higher the surrounding temperature, the faster the concrete cures and vice versa. However, as the relationship is not linear, ongoing monitoring is required.
For the Concrete Maturity, several maturity functions address this ratio, and are also used in the industry, e.g. the Dutch Weighted Maturity, Equivalent Age or Temperature-Time Factor.
CONCRETE MATURITY STANDARDS
Set up and necessary equipment
A measuring device is needed to monitor the temperature. The data has to be gathered either manually, using a local data logger or a wireless transmitter. The temperature data is analysed and maturity and strength are calculated. This data processing is again either a manual task or you can use a software which enables real-time data.
Based on the data, the strength and maturity status is estimated. This serves as a basis for decision making, which actions need to be taken and the optimal time to remove the formwork or to demould is calculated.
- Non-destructive method to estimate concrete strength
- Measuring temperature directly inside the concrete structure
- Immediate procedure
- Continuous information on effective strength development
- Measuring possible at critical positions
- Monitoring in real-time possible
- Maturity Calibration Curve for each concrete recipe required to estimate strength
- Changes in recipe affect the maturity curve
- If the law required the 28 day compression strength test, it can not be replaced. However the number of break tests can be reduced.
Maturix™ VS. Break Tests
Video comparing the accuracy of Maturix™ and compression break tests with concrete cubes
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