The concrete compression test is straightforward but informative. It measures a concrete sample’s quality, its strength contribution to the final structure, and how well it has cured. Most importantly, it ensures that the concrete meets the job’s strength specifications and the quality measures outlined by the ASTM.
How Do You Determine the Compressive Strength of Concrete? A Guide to Concrete Compression Test
When conducting a concrete compression test, follow two key rules: First, the average strengths of three consecutive tests must meet or exceed the job’s specified strength. Second, no test should fall more than 500 psi below the specified strength. Acceptance testing ensures that concrete specimens meet the required strength and compliance standards. Curing concrete test specimens is crucial for accurate compressive strength results. Additionally, the concrete compression test should follow the standard test method outlined in ASTM C39 and be performed according to the following steps.
Standard Test Method Outlined in ASTM C39
- Cylinders must be moist during testing. After curing in a moisture room or similar environment, quickly measure and record each cylinder’s diameter and weight. This data becomes valuable if someone later disputes the test results.
- Ensure that your test machine is clear of debris and set to zero.
- Add either neoprene or sulfur mortar pad caps to the ends of your cylinders. Preferably, this should be done a day before testing.
- Place your specimen in the testing machine. Apply a continuous load without shock until the concrete fails or the machine reaches its maximum capacity. For the first half of loading, a rate of 28-42 psi/second is allowed.
- Remove the cylinder from the machine and take off the caps.
- Calculate the cylinder’s strength in psi. Divide the failure load in pounds by the cylinder’s area in square inches.
- Observe the specimen’s fracture patterns to identify failure causes. Some patterns are acceptable; others suggest issues with concreting, uneven planing, or lubricant presence affecting friction between the cap and cylinder.
What Equipment is Needed to Perform a Concrete Compression Test?
Equipment used for concrete compressive strength tests needs to be strong and stiff to reduce the possibility of explosive failures, which can shock the equipment’s hydraulics and deteriorate its calibration — not to mention the general damage that could shorten its service life. Concrete compression machines are essential in this context, as they load concrete samples until failure according to specific standards, ensuring accurate evaluation of the material’s structural integrity. It also needs to accommodate the pressure capacities to accurately determine the strength of the concrete you’ll be testing.
The compression testing machines from Certified Material Testing Products have the durability and capacities needed for the job, playing a crucial role in determining the compressive strength and durability of concrete. These machines can execute complete test cycles with automatic controllers, performing the entire testing procedure with minimal operator intervention. Our machines range from 7,000-14,100 maximum psi for standard 6×12 concrete cylinders. Digital controllers can also equip them to display load, load rate, and stress during the test, and to store information for later plotting and printing. Besides the concrete compression test machine, using compressometers for efficient data collection is also important.
Compressometers attach to the top and bottom of a concrete cylinder at opposite points to allow pivoting during compression. The digital gauge measures the average deformation and strain that concrete cylinders undergo during compression testing, which is useful if you also test for the modulus of elasticity.
Useful Accessories for Concrete Testing
Finally, it’s always useful to have concrete compression test accessories to help your testing go as smoothly as possible. These could include concrete test cylinder wraps for protecting cylinders as they are transferred to the compression machine or a concrete cylinder lifting handle to help put the specimen securely into place. Each of these tools, and the many others that can be found in our inventory, will help produce the most accurate results and minimize slip-ups.
The Concrete Compression Test is a fundamental and widely used method in civil engineering to determine the compressive strength of concrete. This test ensures that concrete structures like buildings, bridges, and roads meet the required safety and quality standards.
Principle and Compression Testing Machine:
The test involves applying a compressive axial load to concrete test specimens, usually cylindrical concrete specimens or cubes, until they fail. Curing concrete test specimens under standard conditions is crucial for accurate assessment, as it ensures the specimens meet the necessary quality and structural integrity standards. Standard methods, such as those outlined in ASTM procedures, are essential for making and curing concrete test specimens. Evaluating the compressive strength of concrete through quality control is essential. A hydraulic press conducts this test by applying controlled pressure. Technicians prepare and cure the specimen before placing it in the machine. They then apply pressure at a predetermined rate until the specimen fails. Finally, they record the maximum load applied.
Procedure:
Manufacturers typically use cylinders (150mm diameter x 300mm height) or cubes (150mm x 150mm x 150mm) as concrete test specimens. These specimens play a crucial role in assessing the quality of concrete and its load performance. Accurately determining compressive strength requires curing these specimens for a specific period. Workers create them by shaping fresh concrete into cylinders or cubes, then curing them for typically 28 days before conducting tests. During the concrete cube test, the specimen is loaded until failure occurs. Record the breaking load of the concrete specimen. Then calculate the compressive strength by dividing the load by the specimen’s cross-sectional area.
Applications:
The Concrete Compression Test is crucial in the construction industry for quality control purposes. It ensures that the concrete mix design meets the required strength specifications for different construction projects. Researchers and developers also use it to test new concrete mixtures.
Advantages and Limitations:
The main advantage of this test is that it provides a direct measurement of concrete strength. However, the test is destructive and requires careful specimen preparation and curing for accurate results. Additionally, the strength obtained is specific to the specimen and may not represent the overall strength of a structure.
The Concrete Compression Test is vital for assessing concrete’s strength. It offers crucial data for designing and constructing safe concrete structures that meet strength standards.
