31/01/2026
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Practical Civil Engineering Interview Questions, Part 89 – Concrete Testing
(Fresh & Hardened Concrete – Practical & Technical)
1. What is concrete testing?
Concrete testing is the process of checking the properties and quality of concrete to ensure it meets design and specification requirements.
2. Why is concrete testing important on site?
It ensures durability, strength, workability, safety, and compliance with design standards.
3. What are the main types of concrete tests?
Tests on fresh concrete and tests on hardened concrete.
4. What are common tests for fresh concrete?
Slump test, temperature test, air content test, and unit weight test.
5. What is the purpose of the slump test?
To determine the workability and consistency of fresh concrete.
6. How is the slump test performed?
Concrete is placed in a slump cone, compacted, cone removed, and the vertical settlement is measured.
7. What is an acceptable slump range for site concrete?
Typically 50–100 mm for normal reinforced concrete, depending on mix and specifications.
8. Why is temperature monitoring of fresh concrete important?
Extreme temperatures affect hydration, setting time, and strength development.
9. What is the air content test for?
To measure the amount of entrapped or entrained air, especially in freeze-thaw conditions.
10. What tests are done on hardened concrete?
Compressive strength test, flexural strength test, split tensile strength test, and non-destructive tests.
11. How is compressive strength tested?
Concrete samples (cubes or cylinders) are cured and crushed in a compression testing machine to measure maximum load capacity.
12. When are compressive strength tests typically carried out?
At 7 days for early strength and 28 days for design strength.
13. What is a flexural strength test?
A test to determine the bending strength of concrete beams.
14. What is the split tensile strength test?
A test to measure the tensile strength of concrete using cylinders placed horizontally in a compression machine.
15. What are common non-destructive tests (NDT)?
Rebound hammer test, ultrasonic pulse velocity test, and pe*******on resistance tests.
16. Why are non-destructive tests used?
To assess in-situ concrete quality without damaging the structure.
17. How is site sampling for concrete testing done?
By taking representative samples from freshly mixed concrete at different locations of the pour.
18. Why is proper curing important for testing?
Curing ensures hydration, which directly affects the accuracy of strength tests.
19. Who is responsible for concrete testing on site?
Site engineer, quality control engineer, laboratory technician, and site supervisors.
20. How are concrete test results used?
To verify compliance with design strength, adjust mix proportions if necessary and ensure overall structural safety.
By Hussaini Muhammad Sulaiman
