Short Answer:

Tests on concrete are conducted to check its quality, strength, and performance. These tests help engineers ensure that concrete is suitable for construction work. Common tests include slump test, compressive strength test, and compaction factor test.

Other important tests are tensile strength test, durability test, and permeability test. These tests are done on both fresh and hardened concrete to ensure safe and long-lasting structures.

Detailed Explanation:

Tests on concrete

Concrete testing is very important in civil engineering to ensure that the concrete used in construction has the required strength and quality. Different tests are carried out at different stages, such as before placing (fresh concrete) and after hardening (hardened concrete). These tests help in maintaining quality control and preventing failure of structures.

Concrete tests are mainly divided into two categories: tests on fresh concrete and tests on hardened concrete.

Tests on fresh concrete
Fresh concrete tests are performed to check workability, consistency, and ease of handling before it sets.

Slump test is the most common test used to measure workability. In this test, concrete is placed in a cone-shaped mold, and the amount it settles after removing the mold is measured. A higher slump indicates higher workability.

Compaction factor test is used to measure the degree of compaction of concrete. It is useful for low workability concrete. It shows how easily concrete can be compacted.

Vee-Bee test is used for very stiff concrete. It measures the time required for concrete to change shape under vibration. It helps in determining the consistency of concrete.

Flow table test is used for highly workable concrete. It measures how much concrete spreads on a flat surface.

These tests help ensure that concrete can be easily handled and placed in the structure.

Tests on hardened concrete
Hardened concrete tests are conducted after concrete has set and gained strength. These tests check the strength, durability, and other properties.

Compressive strength test is the most important test. Concrete cubes or cylinders are tested under a compression testing machine. The strength is measured after 7 and 28 days.

Tensile strength test checks the ability of concrete to resist tension. Since concrete is weak in tension, this test helps in understanding its behavior under pulling forces.

Flexural strength test measures the ability of concrete to resist bending. It is important for beams and slabs.

Durability test checks the resistance of concrete to weather, chemicals, and environmental conditions. It ensures long life of structures.

Permeability test measures the ability of concrete to resist water penetration. Low permeability is desirable for durable concrete.

Non-destructive tests
Some tests can be performed without damaging the structure. These are called non-destructive tests.

Rebound hammer test is used to check surface hardness and estimate strength. Ultrasonic pulse velocity test is used to detect cracks and defects inside concrete.

These tests are useful for checking existing structures.

Importance of concrete testing
Concrete testing ensures that the material meets required standards. It helps in detecting defects and improving quality.

Testing helps engineers make necessary changes in mix design and construction methods. It also ensures safety and durability of structures.

Without proper testing, there is a risk of weak construction, which can lead to failure.

Conclusion:

Tests on concrete are essential to check its workability, strength, and durability. They include tests on fresh and hardened concrete. Proper testing ensures safe, strong, and long-lasting construction.