Top Best Most Important Basic Civil Engineering Interview Questions with Answers On Concrete Technology

1) What is the initial and final setting time of ideal cement mix?

Ans: Initial setting time for ideal cement mix is around 30 minutes for almost all kinds of cements. For masonry cement it can be 90 minutes. Final setting time of ideal cement mix should be 10 hours at max. For masonry cement it shouldn't exceed 24 hours.

2) What are the common methods of curing the concrete on site?

Ans: -Spraying
         -Wet covering of Surface
         -Ponding
         -Application of curing chemicals
         -Steam curing.

3) What field tests are required for quality check of cement?

Ans: Quality of cement can be checked with color, physical properties, etc. Cement should have grey color with light greenish shade. It should feel smooth when rubbed between the fingers. If hand is inserted in a heap of cement or its bags, it should feel cool. When pinch of cement is thrown in Water then cement should float for some time before it sinks. Also, it should be lump free.

4) What are the types of cement?

Ans: There are various types of cement which are:
      -Ordinary Portland Cement (OPC) 
      -White Portland Cement (WPC) 
      -Portland Pozzolana Cement (PPC)
      -Low Heat Portland Cement
      -Coloured Portland Cement
      -Hydrophobic cement
      -Rapid Hardening Cement
      -Portland Slag Cement
      -Sulphate resisting Portland Cement, etc.

5) What is the factor that helps in converting Wet concrete volume to Dry concrete volume?

Ans: 1.54.

6) What is the temperature at which different ingredients of cement is burnt?

Ans: 14000C.

7) What is the allowable moisture content in fine aggregate for the concrete mix?

Ans: We won’t use the aggregate if its moisture content is more than 5%.

8) What are the test carried out on concrete?

Ans: Slump test, Compressive strength test, Water permeability test, Compaction factor test.

9) What are the units to measure concrete?

Ans: Cubic yards, cubic feet, cubic meters.

10) How much maximum silt content can be allowed in fine aggregate?

Ans: Silt content should not be more than 8% in fine sand.

11) Slump cone is to be filled in how many layers?

Ans: Slump cone is to be filled in 4 layers.

12) How many days curing is done?

Ans: 7 days in normal weather condition.
10  days in dry and hot weather condition.

13) Define fine & course aggregate?

Ans: Aggregate which passes 4.75 mm IS sieve is called fine aggregate.
    Aggregate which retains 4.75 mm IS sieve is called course aggregate.

14) In M-25 explain ‘M’ and ‘25’?

Ans: ‘M’ stands for mix and ‘25’ stands for compressive strength of 150 mm size cube in 28 days, expressed in N/mm2.

15) What is the size of concrete testing cubes/ Compressive strength test?

Ans: 150 mm x 150 mm x 150 mm.

16)  How much size of concrete slump recommended for beam and slab?

Ans: 30 to 125 mm.

17) Which Size of tamping rod as per is 10086:1982 is used to compact concrete cube? 

Ans: 16 mm.

18) What is meant by curing?

Ans: Curing is the application of water to the concrete surface for the proper hydration to occur.

19) What are the causes of cracks in concrete?

Ans: 1) loss of water from surface of concrete
         2) Bleeding of water from concrete
         3) Delayed curing of concrete.

20) What is P.C.C.?

Ans: P.C.C Means:  Plain Cement Concrete.
         It is also called Cement Concrete (C.C.).