32 + Interview Questions in Durability Of Concrete in Concrete Technology Page 1 InterviewSolution

1.	Plain cement concrete is strong in taking ___________(a) Tensile stress(b) Compressive stress(c) Shear stress(d) Tensile, compressive and shear stressesI got this question in an online interview.The question is from Mass Concrete and Chemical Action topic in chapter Durability of Concrete of Concrete Technology
Answer» The correct option is (b) COMPRESSIVE stress The explanation is: Plain cement concrete is strong in TAKING compressive stress and WEEK in tensile stress.

Discussion

2.	The addition of a pozzolanic admixture such as fly ash reduces the ____________(a) C3S(b) C3A(c) C2S(d) C4AFThe question was posed to me in examination.I'm obligated to ask this question of Permeability topic in portion Durability of Concrete of Concrete Technology
Answer» The correct answer is (B) C3A Explanation: The ADDITION of a pozzolanic admixture such as fly ash REDUCES the C3A content of cement.

Discussion

3.	The quality of concrete, specifically a ____________ w/c ratio, is the best protection against sulphate attack.(a) High(b) Medium(c) Low(d) Very lowI have been asked this question in class test.The origin of the question is Permeability topic in portion Durability of Concrete of Concrete Technology
Answer» The correct option is (c) LOW The EXPLANATION: The quality of concrete, specifically a low w/c ratio, is the best protection against sulphate ATTACK.

Discussion

4.	The quality of concrete, specifically a ____________ permeability, is the best protection against sulphate attack.(a) High(b) Medium(c) Low(d) Very lowI had been asked this question in an internship interview.My doubt is from Permeability topic in chapter Durability of Concrete of Concrete Technology
Answer» The correct choice is (C) Low Easiest explanation: The QUALITY of concrete, specifically a low PERMEABILITY, is the best PROTECTION against sulphate attack.

Discussion

5.	What is internal sulphates attack?(a) Presence of natural gypsum in the aggregates(b) Soil may contain excess of gypsum(c) Sulphate are more usually are a result of ground water(d) Industrial waste waterThe question was posed to me in an internship interview.This is a very interesting question from Mass Concrete and Chemical Action topic in section Durability of Concrete of Concrete Technology
Answer» The correct choice is (a) Presence of NATURAL gypsum in the aggregates The explanation is: Internal sulphates attack are rarer but ORIGINATES from such concrete-making MATERIALS LIKE Presence of natural gypsum in the aggregates.

Discussion

6.	When the ____________ content is low, most ettringite will be formed in the plastic state.(a) C3SS(b) C3AA(c) C2S(d) C4AFI have been asked this question during an interview.The question is from Permeability in section Durability of Concrete of Concrete Technology
Answer» Correct option is (B) C3AA The explanation is: When the C3A CONTENT is low, most ettringite will be formed in the plastic state.

Discussion

7.	Approximate ratio of the strength of the cement conc of 7 days to that of 28 days (2/3)?(a) .75(b) .85(c) 1(d) 1.15I got this question in quiz.The query is from Strength and Durability Relationship topic in division Durability of Concrete of Concrete Technology
Answer» Correct answer is (a) .75 The explanation: After the LAB broke the seven-day cylinders, the CYLINDER from the PIER with ADDED water broke at 1980 psi. The other seven-day cylinders were as HIGH as 2620 psi.

Discussion

8.	Harshness in concrete is due to the excess of _____________(a) Water(b) Finer particles(c) Middle sized particle(d) Coarser particleThis question was posed to me during an interview for a job.Query is from Mass Concrete and Chemical Action topic in chapter Durability of Concrete of Concrete Technology
Answer» Correct choice is (c) Middle sized particle Easiest explanation: It is the rough finishing property of CONCRETE and causes IMPROPER proportioning, less compaction, low water CONTENT, excess of MEDIUM sized AGGREGATES, deficiency of sand etc.

Discussion

9.	In order to avoid segregation, the concrete should not be thrown from a height.(a) True(b) FalseI got this question during an interview.My query is from Mass Concrete and Chemical Action topic in chapter Durability of Concrete of Concrete Technology
Answer» The correct option is (a) True For EXPLANATION I WOULD say: In order to avoid SEGREGATION, the CONCRETE should not be thrown from a HEIGHT of 100 cm.

Discussion

10.	Concentration of water-soluble sulphates in water ___________ ppm for severe exposure.(a) 10000This question was addressed to me in final exam.I'd like to ask this question from Permeability topic in chapter Durability of Concrete of Concrete Technology
Answer» Right option is (c) 150-10000 To explain I would SAY: Concentration of water-soluble SULPHATES in water 150-10000 ppm for SEVERE EXPOSURE.

Discussion

11.	Lowering of ____________ might also help, since this would reduce the amount of CH that forms.(a) C3S(b) C3A(c) C2S(d) C4AFI had been asked this question in exam.This intriguing question originated from Permeability topic in division Durability of Concrete of Concrete Technology
Answer» The correct option is (a) C3S To elaborate: Lowering of C3S might ALSO help, since this WOULD reduce the AMOUNT of CH that forms.

Discussion

12.	Concentration of water-soluble sulphates in water ___________ ppm for mild exposure.(a) 10000The question was asked during an online exam.This intriguing question originated from Permeability in section Durability of Concrete of Concrete Technology
Answer» Correct choice is (a) <150 The explanation: CONCENTRATION of water-soluble sulphates in water LESS than 150 ppm for mild EXPOSURE.

Discussion

13.	Strength of concrete increase with _________(a) Increase with w/c ratio(b) Increase in fineness of cement(c) Decrease in size of aggregates(d) Decrease in curing timeI got this question by my college professor while I was bunking the class.Enquiry is from Strength and Durability Relationship in chapter Durability of Concrete of Concrete Technology
Answer» The CORRECT answer is (B) Increase in fineness of cement For EXPLANATION: Strength of concrete increase with increase in fineness of the cement.

Discussion

14.	Strength of concrete is ___________(a) \(f_{ck} = K(\frac{c}{C+W+A})^2\)(b) \(f_{ck} = K(\frac{C+A}{C+W+A})^2\)(c) \(f_{ck} = K(\frac{C+W}{C+W+A})^2\)(d) \(f_{ck} = K(\frac{C+W+A}{C+W+A})^2\)The question was posed to me in an online quiz.I want to ask this question from Strength and Durability Relationship in portion Durability of Concrete of Concrete Technology
Answer» The CORRECT ANSWER is (a) \(f_{ck} = K(\frac{C}{C+W+A})^2\) To explain: It is the formula to find the Strength of concrete when we have the VOLUME of CEMENT, aggregates and water.

Discussion

15.	Strength of concrete show an increase with _________(a) Decrease in rate of loading(b) Increase in rate of loading(c) Unaffected by rate of loading(d) Depends on application of loadThis question was addressed to me in examination.I'd like to ask this question from Strength and Durability Relationship in chapter Durability of Concrete of Concrete Technology
Answer» Right answer is (B) Increase in RATE of loading To EXPLAIN I WOULD say: STRENGTH of concrete is directly proportional to the nature of the loading.

Discussion

16.	Fly ash affects the sulphate attack.(a) True(b) FalseThe question was posed to me in semester exam.This intriguing question comes from Mass Concrete and Chemical Action in chapter Durability of Concrete of Concrete Technology
Answer» Correct CHOICE is (a) True Easiest explanation: The addition of a pozzolanic admixture e.g. fly ash. It reduces the C3A CONTENT of CEMENT which cause sulphates attack.

Discussion

17.	Reinforced cement concrete is equally strong in taking __________(a) Tensile and compressive stresses(b) Compressive and shear stresses(c) Tensile, compressive and shear stresses(d) Tensile and shear stressesThe question was posed to me in my homework.The question is from Mass Concrete and Chemical Action topic in portion Durability of Concrete of Concrete Technology
Answer» CORRECT choice is (c) Tensile, COMPRESSIVE and shear STRESSES The best explanation: ACCORDING to IS 456:2000, Reinforced CEMENT concrete is equally strong in taking Tensile, compressive and shear stresses.

Discussion

18.	The breaking up of cohesion in a mass of concrete is called ________(a) Workability(b) Segregation(c) Bleeding(d) CreepThe question was posed to me in homework.My doubt stems from Mass Concrete and Chemical Action in portion Durability of Concrete of Concrete Technology
Answer» The correct ANSWER is (b) SEGREGATION The BEST explanation: Segregation in concrete is commonly thought as separation of some size groups of aggregates from cement MORTAR in isolated locations with corresponding deficiencies of these materials in other locations.

Discussion

19.	Low w/c ratio helps to control suphate attack.(a) True(b) FalseThe question was posed to me by my college director while I was bunking the class.My doubt stems from Mass Concrete and Chemical Action topic in division Durability of Concrete of Concrete Technology
Answer» CORRECT option is (a) True Easy EXPLANATION: Low WATER cement RATIO directly CAUSE low permeability which is the best protection towards sulphate attack.

Discussion

20.	What is external sulphates attack?(a) Industrial waste water(b) Presence of natural gypsum in the aggregates(c) Hydraulic cements(d) Portland cement might be over-sulphatedThis question was addressed to me in class test.I would like to ask this question from Mass Concrete and Chemical Action topic in division Durability of Concrete of Concrete Technology
Answer» The correct choice is (a) INDUSTRIAL waste water The best EXPLANATION: EXTERNAL sources of SULPHATE are very common and are usually are a result of high-sulphate soils and ground waters or can be result into industrial POLLUTION.

Discussion

21.	The separation of water or water-cement mixture from the freshly mixed concrete is known as bleeding.(a) True(b) FalseI have been asked this question in a national level competition.Origin of the question is Mass Concrete and Chemical Action topic in section Durability of Concrete of Concrete Technology
Answer» CORRECT answer is (a) True The explanation: The SEPARATION of WATER or water-cement mixture from the freshly mixed CONCRETE is KNOWN as bleeding.

Discussion

22.	For concrete exposed to a very aggressive environment the w/c should be lower than __________(a) 1(b) .5(c) .4(d) .8This question was posed to me in my homework.This interesting question is from Permeability topic in chapter Durability of Concrete of Concrete Technology
Answer» The correct option is (c) .4 Best EXPLANATION: Higher is the aggressiveness of the environment lower should be the w/c ratio. For CONCRETE EXPOSED to a very AGGRESSIVE environment, the w/c should be lower than 0.40.

Discussion

23.	Strength of concrete increase with _____________(a) Increase with w/c ratio(b) Decrease with w/c ratio(c) Decrease in size of aggregates(d) Decrease in curing timeThe question was asked in semester exam.Question is from Strength and Durability Relationship in chapter Durability of Concrete of Concrete Technology
Answer» Correct choice is (B) Decrease with w/c ratio The BEST I can explain: As mentioned above that STRENGTH of CONCRETE is INVERSELY proportional to w/c ratio.

Discussion

24.	Strength of concrete is proportional to ______________(a) Sand content(b) Water cement ratio(c) Aggregate ratio(d) Cement water ratioI have been asked this question in an online quiz.The query is from Strength and Durability Relationship in portion Durability of Concrete of Concrete Technology
Answer» Correct answer is (d) CEMENT water ratio The explanation is: STRENGTH of concrete is PROPORTIONAL to Cement water ratio and INVERSELY proportional to w/c ratio.

Discussion

25.	Approximate ratio of strength of the 30 cm cube to that of 15 cm cube is _____________(a) 1.1(b) 1(c) .9(d) .75The question was posed to me in a national level competition.I'm obligated to ask this question of Strength and Durability Relationship in division Durability of Concrete of Concrete Technology
Answer» Right OPTION is (c) .9 For explanation: The strength of cylinder with diameter of 15cm and 30cm tall can be approximated as 0.84 of the strength of a 15x15x15 cm cube ACCORDING to Eurocodes.

Discussion

26.	As per & 5456:200 Young’s modulus of concrete is _______________(a) 1000 fck(b) 5000 fck^2(c) 5700 fck(d) 150 fckI got this question in an online interview.My question is based upon Strength and Durability Relationship in division Durability of Concrete of Concrete Technology
Answer» The correct choice is (b) 5000 fck^2 The explanation: 5000 fck^2 is the formula of YOUNG’s modulus of the CONCRETE according to IS 5456:200.

Discussion

27.	How many types of sulphates attack occur in concrete?(a) 1(b) 2(c) 3(d) 4I had been asked this question in unit test.I would like to ask this question from Mass Concrete and Chemical Action in chapter Durability of Concrete of Concrete Technology
Answer» The correct option is (b) 2 Explanation: There are two TYPES of sulphates ATTACK in CONCRETE and mortar i.e., INTERNAL attack and external attack.

Discussion

28.	The continuous strain, which the concrete undergoes due to application of external loads, is called __________(a) Workability(b) Segregation(c) Bleeding(d) CreepI got this question in a national level competition.The origin of the question is Mass Concrete and Chemical Action topic in portion Durability of Concrete of Concrete Technology
Answer» Right ANSWER is (d) CREEP Easy explanation: The CONTINUOUS strain, which the concrete undergoes due to APPLICATION of EXTERNAL loads, is called creep.

Discussion

29.	Approximate ratio of direct tensile strength to flexural strength is ____________(a) .25(b) .33(c) .5(d) .05The question was posed to me in a national level competition.The question is from Strength and Durability Relationship topic in portion Durability of Concrete of Concrete Technology
Answer» Correct ANSWER is (c) .5 To EXPLAIN I would SAY: Approximate ratio of direct tensile strength to flexural strength is .5 ACCORDING to the formula.

Discussion

30.	Durability of concrete is proportional to _________(a) Sand content(b) Water cement ratio(c) Aggregate ratio(d) Cement aggregate ratioThis question was addressed to me by my school principal while I was bunking the class.This question is from Strength and Durability Relationship topic in portion Durability of Concrete of Concrete Technology
Answer» Right option is (d) CEMENT AGGREGATE ratio Explanation: VOLUME chances due to difference in thermal properties of the aggregates and cement PASTE.

Discussion

31.	The quality of concrete, specifically a ____________ cement content, is the best protection against sulphate attack.(a) High(b) Medium(c) Low(d) Very lowThe question was posed to me in semester exam.The query is from Permeability in section Durability of Concrete of Concrete Technology
Answer» RIGHT ANSWER is (a) HIGH To explain I would say: The quality of concrete, specifically a high cement content, is the BEST protection against sulphate ATTACK.

Discussion

32.	The philosophy of prescribing low ____________ cement to improve resistance to sulphate attack.(a) C3S(b) C3A(c) C2S(d) C4AFI got this question by my college director while I was bunking the class.Question is taken from Permeability topic in chapter Durability of Concrete of Concrete Technology
Answer» Correct ANSWER is (b) C3A The best explanation: The philosophy of prescribing low C3A cement to improve resistance to SULPHATE ATTACK hinges on the NEED to minimize ettringite formation after the concrete hardens.

Discussion

Explore topic-wise InterviewSolutions in .

The addition of a pozzolanic admixture such as fly ash reduces the ____________(a) C3S(b) C3A(c) C2S(d) C4AFThe question was posed to me in examination.I'm obligated to ask this question of Permeability topic in portion Durability of Concrete of Concrete Technology

The quality of concrete, specifically a ____________ w/c ratio, is the best protection against sulphate attack.(a) High(b) Medium(c) Low(d) Very lowI have been asked this question in class test.The origin of the question is Permeability topic in portion Durability of Concrete of Concrete Technology

When the ____________ content is low, most ettringite will be formed in the plastic state.(a) C3SS(b) C3AA(c) C2S(d) C4AFI have been asked this question during an interview.The question is from Permeability in section Durability of Concrete of Concrete Technology

Approximate ratio of the strength of the cement conc of 7 days to that of 28 days (2/3)?(a) .75(b) .85(c) 1(d) 1.15I got this question in quiz.The query is from Strength and Durability Relationship topic in division Durability of Concrete of Concrete Technology

In order to avoid segregation, the concrete should not be thrown from a height.(a) True(b) FalseI got this question during an interview.My query is from Mass Concrete and Chemical Action topic in chapter Durability of Concrete of Concrete Technology

Concentration of water-soluble sulphates in water ___________ ppm for severe exposure.(a) 10000This question was addressed to me in final exam.I'd like to ask this question from Permeability topic in chapter Durability of Concrete of Concrete Technology

Lowering of ____________ might also help, since this would reduce the amount of CH that forms.(a) C3S(b) C3A(c) C2S(d) C4AFI had been asked this question in exam.This intriguing question originated from Permeability topic in division Durability of Concrete of Concrete Technology

Concentration of water-soluble sulphates in water ___________ ppm for mild exposure.(a) 10000The question was asked during an online exam.This intriguing question originated from Permeability in section Durability of Concrete of Concrete Technology

Fly ash affects the sulphate attack.(a) True(b) FalseThe question was posed to me in semester exam.This intriguing question comes from Mass Concrete and Chemical Action in chapter Durability of Concrete of Concrete Technology

The breaking up of cohesion in a mass of concrete is called ________(a) Workability(b) Segregation(c) Bleeding(d) CreepThe question was posed to me in homework.My doubt stems from Mass Concrete and Chemical Action in portion Durability of Concrete of Concrete Technology

Low w/c ratio helps to control suphate attack.(a) True(b) FalseThe question was posed to me by my college director while I was bunking the class.My doubt stems from Mass Concrete and Chemical Action topic in division Durability of Concrete of Concrete Technology

For concrete exposed to a very aggressive environment the w/c should be lower than __________(a) 1(b) .5(c) .4(d) .8This question was posed to me in my homework.This interesting question is from Permeability topic in chapter Durability of Concrete of Concrete Technology

Strength of concrete is proportional to ______________(a) Sand content(b) Water cement ratio(c) Aggregate ratio(d) Cement water ratioI have been asked this question in an online quiz.The query is from Strength and Durability Relationship in portion Durability of Concrete of Concrete Technology

As per & 5456:200 Young’s modulus of concrete is _______________(a) 1000 fck(b) 5000 fck^2(c) 5700 fck(d) 150 fckI got this question in an online interview.My question is based upon Strength and Durability Relationship in division Durability of Concrete of Concrete Technology

How many types of sulphates attack occur in concrete?(a) 1(b) 2(c) 3(d) 4I had been asked this question in unit test.I would like to ask this question from Mass Concrete and Chemical Action in chapter Durability of Concrete of Concrete Technology

Approximate ratio of direct tensile strength to flexural strength is ____________(a) .25(b) .33(c) .5(d) .05The question was posed to me in a national level competition.The question is from Strength and Durability Relationship topic in portion Durability of Concrete of Concrete Technology

The quality of concrete, specifically a ____________ cement content, is the best protection against sulphate attack.(a) High(b) Medium(c) Low(d) Very lowThe question was posed to me in semester exam.The query is from Permeability in section Durability of Concrete of Concrete Technology

The philosophy of prescribing low ____________ cement to improve resistance to sulphate attack.(a) C3S(b) C3A(c) C2S(d) C4AFI got this question by my college director while I was bunking the class.Question is taken from Permeability topic in chapter Durability of Concrete of Concrete Technology