Here are the top 50 commonly asked questions in Concrete Technology interviews. Whether you’re just starting your preparation or need a quick refresher, these questions and answers will help you tackle your interview with confidence.
Basic Concrete Technology Interview Questions with Answers
1. What is concrete technology?
Concrete technology is the study of properties of concrete. It deals with the practical applications of concrete for any construction.
2. How is concrete defined in Concrete Technology?
Concrete is defined as a mixture of coarse and fine aggregates bonded together by cement and water. Concrete after placing becomes hard and provides strength to the structure.
3. What is reinforced concrete in Concrete Technology?
Reinforced concrete is formed by providing steel reinforcements in the concrete to increase the tensile strength and ductility of concrete.
4. What are the factors affecting durability of concrete in the study of Concrete Technology?
The factors affecting durability of concrete are cement content, water/cement ratio, compaction, curing and permeability.
5. What is the purpose of adding plasticizers to Concrete?
Plasticizers are added to concrete to allow the release of water trapped in the pores to increase the workability of concrete.
6. Why are super plasticizers added to concrete in Concrete Technology?
These are added to concrete to reduce the water/cement ratio. These help in the formation of self consolidating and high performance concrete.
7. What are the advantages of concrete?
Concrete has high strength, durability, lowest carbon footprint, fire resistant, rust proof, more safety and security.
8. Which material can replace cement as a binder in Concrete?
Metakaline is the most effective pozzolanic material having binding properties and can be used as a replacement of cement in concrete.
9. What is the minimum grade of Concrete to be used in reinforced concrete structures according to IS-456-2000?
As per IS-456-2000, the minimum grade of concrete for RCC work should not be less than M20 grade.
10. What are different grades of concrete in Concrete Technology?
Different grades of concrete have different mix proportions of materials like cement, sand, coarse aggregates. Grades start as M5, M10, M15, M20, M25 up to M100. However, higher grades can be made by altering the mix proportions.
11. What is the density of normal Concrete?
The density of normal concrete is in between 2240 kilogram per cubic meter to 2400 kilogram per cubic meter.
12. What is the compressive strength of normal Concrete?
The compressive strength of normal concrete should be more than 70 megapascals. Different grades of concrete have different compressive strengths.
13. How is light weight concrete better than normal concrete in Concrete Technology?
Light weight concrete is less denser than normal concrete. Light weight aggregates are used in it’s formation.
14. What are the uses of light weight concrete as mentioned in Concrete Technology?
These are used in long span bridge docks, fire and corrosion protection, heat insulation on roofs, framed structures.
15. What is compacting factor in Concrete Technology?
It is the ratio of weight of partially compacted concrete to weight of fully compacted concrete.
16. What should be the density and compressive strength of light weight Concrete?
The density of light weight concrete is in between 1840-1940 kilogram per cubic meter. It’s compressive strength should be 45 megapascals.
17. What is the purpose of curing of concrete in Concrete Technology?
Curing of concrete is done to increase the hydration process of cement fractions in concrete. It is the slow release of water present in pores of concrete.
18. What factors of Concrete are affected by shape of aggregates used?
Round shaped aggregates increase the workability, angular shaped aggregates increase bond strength of the concrete.
19. What is design mix of concrete in Concrete Technology?
It is not used for simple concrete works and every ingredient of concrete undergoes the lab tests for determination of it’s properties.
20. What are the objectives of Concrete design mix?
Objective of concrete design mix is to determine properties of concrete constituents, to produce concrete of specific properties, to make it as economical as possible.
Intermediate Concrete Technology Interview Questions with Answers
21. What are main ingredients of concrete?
Concrete consists of fine aggregates, coarse aggregates, cement and water mixed with each other.
22. What are the methods of manufacture of portland cement?
Dry process and wet process are two methods of manufacture of portland cement.
23. Why is gypsum added to concrete?
Gypsum is added to increase the setting time of concrete.
24. Who invented reinforced concrete?
A gardener from France named Joseph Monier invented the reinforced concrete by inserting an iron mesh into his pots to make the walls more strong.
25. Which chemical compounds provide strength to concrete?
Tricalcium silicate and dicalcium silicate are main chemical compounds responsible for providing strength.
26. What is heat of hydration?
The reaction of cement and water is exothermic in nature and liberates a lot of heat. This liberation of heat is known as heat of hydration.
27. How is quick setting cement formed?
This type of cement is formed by reducing the gypsum content at the time of clinker grinding.
28. What are air entraining agents?
Air-entraining agents are also known as pore-forming agents, these compounds helps in entraining microscopic air bubbles into cement compositions.
29. Which IS code governs the manufacturing of coloured cement?
Manufacturing of coloured cement is done as per IS-8042-1989.
30. Which type of concrete is used in formation of railway sleepers?
IRS T-40 special grade cement concrete is used for making railway sleepers as per code IRS T-40. 1985.
31. What does bulk density of aggregates represent?
The bulk density of aggregates give valuable information about the shape and grading of aggregates.
32. What are admixtures?
These are defined as a material added to concrete before or during mixing process to alter some properties of concrete.
33. What are retarders?
A retarder is an admixture that slows down the hydration process so that concrete remains plastic and workable for long time.
34. What are the examples of artificial pozzolanic materials?
Fly ash, blast furnace slag, silica fume, surkhi and metakoline are some examples of pozzolanic materials.
35. What are factors affecting workability of concrete?
Water content, size of aggregates, surface texture, shape, grading of aggregates, use of admixtures and mix proportions are some factors affecting workability of concrete.
36. Which property of concrete is calculated by Slump test?
Slump test is most commonly used method of measuring consistency of concrete.
37. What is the reason of curing?
Curing of concrete increases the hydration process of cement present in concrete. It slowly releases the water trapped in pores of concrete.
38. What are different properties of light weight concrete?
Different properties of light weight concrete are size, shape and texture of aggregates, compressive strength, internal curing, fire endurance.
39. What is Vee Bee consistometer test.
Vee Bee consistometer test is an indirect test to measure the workability of concrete.
40. How will you define segregation of concrete?
Segregation is defined as the separation of constituent materials of concrete. It is breaking up of concrete aggregates from rest of the ingredients.
41. What phenomenon does concrete show when it gains excess of water?
The excess of water gain is termed as bleeding. Due to bleeding, water comes up on the surface along with cement.
42. Which term is used for proportioning of materials in concrete manufacturing?
Weight batching is used for proportioning of materials. In the preparation of specific grades of concrete the ingredients are added according to mix proportions with respect to their weights.
43. What is slip form technique?
Slip forming of construction is a method generally adopted for tall structures. In this technique a certain movable mechanism is used and continuous placing and compaction is done layer by layer.
44. What are different methods of curing?
Different methods of curing are water curing, membrane curing, application of heat.
45. How is strength of concrete affected?
Strength of concrete is affected due to water to cement ratio, cement to aggregate ratio, surface texture, shape, size of aggregates, maximum size of aggregates.
46. According to IS-456-2000, what is the relation of flexural strength with compressive strength?
The relation between flexural strength and compressive strength is represented as. flexural strength = 0.7(compressive strength)0.5.
47. What is creep of concrete?
Creep of concrete is defined as strain occurring in the structure due to continuous applied load.
48. What is shrinkage of concrete?
It is defined as volume change occurring in the concrete body.
49. What are different types of shrinkage?
Different types of shrinkage are plastic shrinkage, drying shrinkage, autogeneous shrinkage and carbonation shrinkage.
50. What is the main factor affecting shrinkage?
Relative humidity of the atmosphere at which the concrete specimen is kept is the main factor affecting it’s shrinkage.
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