GTU Concrete Technology Question Paper

GUJARAT TECHNOLOGICAL UNIVERSITY

BE SEM-III Examination May 2012

Subject Name: Concrete Technology

Time: 02.30 pm – 05.00 pm Total Marks: 70

Instructions:

  1. Attempt all questions.
  2. Make suitable assumptions wherever necessary.
  3. Figures to the right indicate full marks.

Draw flow chart and explain manufacturing of cement by wet process.              07

What are the major Bogue’s compounds of cement? Discuss their role in 07 hydration of cement.

Give the classification of aggregate based on shape.                                         07

What is bulking of sand? How it is determined in laboratory?                           07

OR

Describe aggregate impact value test.                                                             07

Explain methods of transporting concrete.                                                      07

Differentiate between volume batching and weigh batching in concrete 07 mix procedure.

OR

Explain rebound hammer test.                                                                       07

Write short note on fiber reinforced concrete.                                                 07

What is effect of freezing and thawing on concrete?                                        07

Write short note on acid attack on concrete.                                                    07

OR

Explain vacuum concreting technique.                                                           07

Define creep. Explain factors affecting on creep.                                             07

What are the factors affecting on choice of mix design?                                   07

Explain crack repair by routing and sealing.                                                   07

OR

Explain adverse effect of excessive use of admixtures.                                     07

Using IS method of mix design, find out proportions of concrete for 07 following data:

Grade of Concrete: M 25 Degree of Control: Good Maximum size of Aggregate: 20 mm Specific gravity of Cement: 3.15 Specific gravity of FA: 2.62 Specific gravity of CA: 2.64 Condition of Exposure: Moderate Workability: 0.90 CF

Note: 5% of the low results are acceptable and W/C ratio for 28 days strength of concrete is 0.49. Refer table 1 to 6.

 

Table – 1: Suggested value of standard deviation

Grade of Concrete

Standard Deviation for Different Degree of Control

Very good

Good

Fair

M 10

2.0

2.3

3.3

M 15

2.5

3.5

4.5

M 20

3.6

4.6

5.6

M 25

4.3

5.3

6.5

M 30

5.0

6.0

7.0

 

Table – 2 Value of ‘t’

Accepted Proportion of Low Results

Value of

‘t’

1 in 5

0.84

1 in 10

1.28

1 in 15

1.5

1 in 20

1.65

1 in 40

1.86

1 in 100

2.33

 

Table – 3 Values of W/C ratio and compressive strength

Compressive Strength in N/mm2 at 28 days

W/C ratio

20

0.600

25

0.525

30

0.480

35

0.420

40

0.375

45

0.335

 

Table – 4 W/C ratios as per Durability Requirements

Exposure Condition

Maximum W/C ratio

Mild

0.65

Moderate

0.55

Severe

0.45

 

Table – 5 Approximately sane

and water content per m3 of concrete for grade up to M 35

Nominal maximum size of aggregate mm

Water content per meter cube of concrete in kg

Sand as % of total aggregate by absolute volume

10

208

40

20

186

35

40

165

30

Table – 6 Approximate Air Content

 

 

Nominal Maximum size of Aggregate mm

Entrapped air as % of volume of concrete

10

3.0

20

2.0

40

1.0

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