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 acceler**

**ated 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**

**upon.**

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 Hard**

**ened 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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