Wednesday, August 25, 2010

Concrete Technology - Unit 4

Year: III
Semester: I

Frequently Asked Questions (FAQ)

Unit - 4: Hardened Concrete

1. (a) Explain the relation between tensile strength and compressive strength of concrete.
(b) Explain various factors that will effect the strength of concrete.

2. (a) What is accelerated curing? Explain its significance?
(b) Describe the procedure for assessment of compressive strength using accelerated curing method as per BIS.

3. (a) Explain Maturity concept of concrete?
(b) Discuss the Abrams water/cement ration law and its significance. How strength of concrete is estimated by w/c ratio law.

4. (a) What is the classification of concrete based on strength as per IS456.2000?
(b) Explain the method of determining flexural strength of concrete?

5. (a) Explain Maturity concept of concrete?
(b) The strength of a sample of fully matured concrete is found to be 30Mpa. Find the strength of identical concrete at age of 7 days when cured at an average temperature during daytime 14 hours at 280C and nighttime 10 hours at 150. The plowman’s constants A and B are 21 and 61 respectively.

6. (a) Explain in detail the gain of strength of concrete with age.
(b) Explain different methods of curing of concrete

7. (a) Explain the significance on gel/space ratio.
(b) Explain calculation of gel space ratio for complete hydration and partial hydration of cement.

8. List out and explain factors on which the properties of hardened concrete depends

9. (a) State and explain Abram’s w/c ratio law. Discuss its limitations.
(b) Draw the normal curves depicting the variation of compressive strength of concrete with w/c ratio and cement /water ratio.

10. (a) What do you understand by “Grade of concrete”? Discuss different grades of concrete as per IS-456-2000.
(b) Describe in detail the Accerlated curing test for concrete? Bring out its advantages and limitations.

11. (a) How does the maximum size of coarse aggregate affects the strength of Hardened concrete.
(b) Laboratory experiments conducted in Mumbai on a particular mix showed a strength of 33 MP a for a fully matured concrete. Find whether formwork can be removed for an identical concrete placed at Jammu at the age of 15 days when the average temperature is 60C. The stripping stress in concrete may be taken as 25 Mpa.The Plowman’s Constants may be assumed as 21 and 61.

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