How do we ensure that the concrete used meets the required standards? This is where the concrete cylinder compression test comes into play. This test helps engineers determine the maximum compressive stress a concrete cylinder can withstand under a gradually applied load without breaking. It provides invaluable insights into concrete’s strength, ensuring it meets criteria and contributes to the safety of structures.
This post will explore the Concrete Cylinder Compression Test. We’ll cover how strength is measured, its importance in construction, essential precautions, and more.
Understanding Concrete Cylinder Compression Test
The Concrete cylinder compression test measures the strength of hardened concrete, assessing its capacity to withstand loads before failure. As the name suggests, it involves compressive strength testing by crushing concrete in a compression testing machine.
Many tests are conducted on concrete to ensure its quality and suitability for various construction applications.
However, engineers in structural design frequently use the compressive strength test as a popular performance measure because it provides contractors with information on the strength of concrete and how these potentially increase over time.
In most cases, concrete typically reaches full strength at 28 days, with 75% of this strength achieved in 7 days. Over time, concrete’s strength can increase due to hydration. Hydration is a chemical reaction where the primary compound in cement forms chemical bonds with water molecules. Water absorbs into the concrete, increasing its strength for years.
What is the Required Compressive Strength of a Concrete Cylinder?
The required compressive strength of a concrete cylinder can vary depending on the structure you are building. Concrete’s compressive strength is crucial for structural evaluation and design and factors such as load-bearing capacity.
If your design is residential, the strength can range from 2500 psi (17 MPa) for residential concrete to 4000 psi (28 MPa). The required strength is higher for commercial structures. Higher strengths exceeding 10,000 psi (70 MPa) are for specific applications.
What is the Standard for the Compressive Strength of Cylindrical Concrete?
For over 80 years, ASTM C39 has been the industry standard test method for measuring the compressive strength of concrete molds. Proper capping of concrete sample is crucial in preparing them for compressive strength testing according to ASTM standards.
ASTM C39 specifies the technique for determining the strength of concrete samples like molded cylinders and drilled cores.
This test method’s results form the foundation for quality control of concrete proportioning and mixing, and departments of transportation use them to verify that roadways and bridges are safe for travel and will last the expected lifespan.
You may also like: ASTM Tests: A Guide for Material Testing in Construction.
What is the Formula for the Compressive Strength of Concrete?
According to ASTM C39/C39M, the compressive strength of a concrete specimen (cylinder) is calculated by dividing the maximum load applied during the test by the area. Compressive strength tests are crucial for determining the load rate sensitivity of concrete, emphasizing the importance of accurate and repeatable control rates.
Compute this area by averaging the two measured diameters of the cylinders or the side dimensions of the cubes.
Technicians typically test concrete’s strength at 7-day intervals and every 28 days in pairs. We determine conformance by comparing the results to the project specification.
Results are expressed to the nearest 10 psi (0.1 MPa). Here is the formula for calculating the compressive strength of concrete:
- Compressive Strength = Maximum Load / Area
Equipment for Concrete Cylinder Compression Test
The equipment used in concrete cylinder tests are:
Cylinder mold of 150 mL diameter and 300 mL height or 100 x 200 mL
Concrete mix preparation and handling are crucial for accurate test results. Issues such as incorrect mix proportions, poor compaction, and wrong curing can affect the quality of the concrete mix and lead to potential errors in test outcomes.
Note that the diameter of the cylinder cast must be at least three times the nominal maximum size of the coarse aggregate material used in concrete production.
Also, the sample cylinder can have either of the two dimensions described above.
Procedure for Compressive Strength Tests of Concrete Cylinders
The concrete cylinder testing procedure has two phases. The concrete cylinder test is significant in the construction industry for assessing the compressive strength of concrete specimens. Phase one is preparing the sample, and phase two is the actual test. Testing concrete cylinders is crucial for quality control and ensuring compliance with project specifications. Concrete testing involves various methods and equipment, including standard cured tests. Proper testing is essential for maintaining the integrity of concrete structures by verifying their strength. Following guidelines and best practices for handling, curing, and testing is vital for safe and durable structures.
The concrete cylinder compression test is a crucial procedure in the construction industry, used to determine the compressive strength of concrete. This test helps engineers and contractors assess the ability of concrete to withstand axial loads without breaking, ensuring that the material meets strength requirements for structural applications.
The process involves creating concrete specimens, typically 150 mm in diameter and 300 mm in height. These specimens are cured under controlled conditions and then subjected to a gradual, axial load in a compression testing machine. The maximum load applied to the cylinder before it fails is recorded, and the compressive strength is calculated by dividing this load by the area.
Summary
Compressive strength is a key indicator of concrete quality and performance. High strength implies that the concrete can withstand significant loads, contributing to the safety of the structures. It ensures that the material can support the intended structural loads without experiencing failure.
Conducting the concrete cylinder compression test involves several important steps. First, properly prepare the specimens. Then, handle them carefully to avoid damage. Next, accurately calibrate the testing equipment. Following standardized procedures, such as those outlined by ASTM C39, is essential to ensure reliable and consistent results.
The data obtained from the concrete cylinder test provide valuable insights into the material’s properties. This information allows engineers to make informed decisions about mix design, quality control, and suitability for specific construction projects. By verifying that the concrete meets required standards, this test ensures the structural integrity of buildings, bridges, and other infrastructure.
