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Posted By: Sri Member Level: Gold Posted Date: 12 Dec 2007
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2006 Jawaharlal Nehru Technological University B.Tech Civil III/Sem1 Regular (NOV)Set 1,CONCRETE TECHNOLOGY AND PRESTRESSED CONCRETE Question paper
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Code No: RR310101 Set No. 1
III B.Tech I Semester Regular Examinations, November 2006
CONCRETE TECHNOLOGY AND PRESTRESSED CONCRETE
(Civil Engineering)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
? ? ? ? ?
1. (a) Discuss in detail how the chemical composition of cement affects its strength& setting properties.
(b) Explain the difference between Natural and Artificial cement.[10+6]
2. (a) ”The bulk density of aggregate gives valuable information regarding its shape
and grading”. Explain this statement.
(b) Explain the laboratory tests to determine the bulk density of aggregates.[8+8]
3. Compressive Strength Test was conducted on six cubes of size 150 X 150 X 150mm.Theultimate loads recorded are 456KN, 450KN, 462KN, 458KN,455KN, 450KN.Compressivestrength test on six cylinders of size 150mm dia X300 mm height of same concreterecorded following ultimate loads. 288KN, 292KN,297KN,293KN,292KN, 290KNfor the above results calculate.
(a) Cube Compressive Strength
(b) Cylinder Compressive Strength
(c) Comment on grade of concrete
(d) Ratio of cylinder strength to cube strength.[4+4+4+4]
4. (a) Describe in detail the Absolute volume method of Mix Design.
(b) For a particular concrete Mix, the details are as given below.
Specific Gravity of Cement = 3.10
Specific Gravity of Fine Aggregate = 2.70
Specific Gravity of coarse aggregate = 2.72
Total water content = 190Kg/Cum of concrete
Entrapped air content = 2%
Total cement content = 380 kg/cum of concrete
Percentage of fine aggregate = 34%
Using absolute volumes, calculate the quantities of coarse aggregate and fine
aggregate required for one cubic meter of concrete.[8+8]
5. A pre-stressed concrete beam section is 250 mm wide and 300 mm deep. The initial
Pre-stressing force is 450 KN at an eccentricity of 60 mm. The beam has a span of
5.75 m and has to carry a superimposed load of 7.50 KN/m. Analyze the beam
section for the stresses produced at mid span before and after the application of
the live load. Allow a loss of pre-stress at 15 % . Take weight of concrete equal to
24KN/m3. [16]
6. A pre-stressed concrete beam of rectangular cross section 160mm wide and 330mm
deep is pre-stressed by 8 wires of 7mm diameter wires located at 110mm from the
soffit of the beam. If the wires are initially tensioned to a stress of 1200MPa.
Calculate the stresses at transfer and the effective stress after all losses. Take
ES = 208kN/mm2 EC = 33.5kN/mm2 Give the following data.
Up to time of transfer Final stage
(a) Relaxation of steel 37N/mm2 69MPa
(b) Shrinkage of concrete 101x10-6 309x10-6
(c) Creep of concrete - 59x10-6 per MPa.[16]
7. A pre-stressed concrete beam of uniform rectangular cross section and span 15 m
supports a total distributed load of 272 KN excluding the weight of the beam.
Determine the suitable dimensions of the beam and calculate the area of the ten-
dons and their position. The permissible stresses are 14N/mm2 for concrete and
1050N/mm2 for the tendons. [16]
8. A pre-stressed beam of rectangular section 20 cm x 45 cm is pre-stressed by a triangular tendon carrying an effective pre-stress of 350 KN. It has a maximum eccentricity
of 100 mm at mid span. The beam supports a uniform load of 10 KN/m over a
span of 10 m. Determine the principal stresses at the support section. [16]
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