Objective concrete Technology part-4

Most important question from concrete Technology (CT) 

Ques 1.  The surface where two successive placements of concrete meet, is known as
(a) contraction joint
(b) expansion joint
(c) construction joint
(d) both (a) and (b)
Ans- c
Ques 2. Pick up the correct statement from the following:
(a) water cement paste hardens due to hydration
(b) during hardening cement binds the aggregates together
(c) cement provides strength, durability and water tightness to the concrete
(d) all the above
Ans- d
Ques 3. If in a concrete mix, water cement ratio is such that water is just sufficient to hydrate each cement particle fully, then
(a) cement paste will give lowest strength
(b) cement paste will give maximum strength
(c) cement paste will cause bleeding
(d) both (a) and (c)
Ans- a
Ques 4. 'Ware house pack' of cement means
(a) full capacity of the ware house
(b) pressure exertion of the bags of upper layers
(c) pressure compaction of the bags on  lower layers
(d) packing the ware house
Ans- c
Ques 5. Active compounds of cement when reacts with water, cause
(a) initial setting of cement
(b) final setting of cement
(c) contributes little after 24 to 72 hours
(d) both (a) and (c)
Ans- d
Ques 6. The reaction of C3S is responsible for strength development for the
(a) first 14 days
(b) first 28 days
(c) whole life
(d) first three years
Ans- b
Ques 7. The reaction of C2S is responsible for
(a) earlier strength of concrete
(b) later strength of concrete
(c) both (a) and (b)
(d) neither (a) nor (b)
Ans- b
Ques 8. In concrete, compressive strength developed after 28 days is 75% of the
(a) initial strength
(b) strength after 3 years
(c) strength after 5 years
(d) ultimate strength
Ans- d
Ques 9. Reaction product after hydration, consists of
(a) calcium aluminate
(b) calcium hydroxide
(c) calcium silicate
(d) all these
Ans- d
Ques 10. A beam curved in plan is designed for
(a) bending moment and shear
(b) bending moment and torsion
(c) shear and torsion
(d) bending moment, shear and torsion
Ans- d
Ques 11. The composition of calcium hydroxide and hydrated calcium silicates, is called
(a) Portland cement
(b) high alumina cement
(c) cement gel
(d) none of these
Ans- c
Ques 12. High alumina cement is produced by fusing together a mixture of
 (a) limestone and bauxite
(b) limestone, bauxite and gypsum
(c) limestone, gypsum and clay
(d) limestone, gypsum, bauxite and clay    
Ans- a
Ques 13. During hydration, cement gel
(a) increases in volume
(b) decreases in volume
(c) causes segregation
(d) causes bleeding
Ans- a
Ques 14. The total volume occupied by gel after full hydration is
(a) more than the volume of water and cement before hydration
(b) less than the volume of water and cement before hydration
(c) same as the volume of water and cement before hydration
(d) none of these
Ans- c
Ques 15. If in a concrete mix, water cement ratio is such that water is more than required for full hydration each cement particle fully, then
(a) free water occupies certain space in concrete
(b) free water evaporates leaving behind pores
(c) strength of concrete will reduce
(d) all of the above
Ans- d
Ques 16. According to Duff Abram, water-cement ratio is related to compressive strength of concrete as per equation(x = w/c ratio by volume, S = compressive strength of concrete)
(a) S = 948/7x
(b) S = 7x/948
(c) S = 948(7x)
(d) none of these
Ans- a
Ques 17. Strength of concrete is proportional to
(a) water content in cement
(b) cement content in concrete
(c) sand content in cement
(d) water-cement ratio
Ans- d
Ques 18. To avoid evaporation of water from pores in concrete during hydration, internal moisture conditions should be maintained. This statement is
(a) false
(b) nonsense
(c) true
(d) debatable
Ans- c
Ques 19. For determining compressive strength of concrete, size of specimen cube is
(a) 10 cm
(b) 15 cm
(c) 20 cm
(d) 30 cm
Ans- b
Ques 20. The approximate ratio of strength of 15 cm x 30 cm concrete cylinder to that of 15 cm cube of the same concrete is
 (a) 1.25
(b) 1.00
(c) 0.85
(d) 0.50
Ans- c
Ques 21. Compressive strength of concrete(in N/mm2) is specified at
(a) 270C ± 30C
(b) 28 days age
(c) 90% relative humidity
(d) all these
Ans- d
Ques 22. In a given concrete mix, if 25 kg of water is added per 50 kg of cement, then w/c ratio is
(a) 2
(b) 0.5
(c) 1
(d) none of these
Ans- b
Ques 23. High carbon content in the steel causes
(a) decrease in tensile strength but increase in ductility
(b) increase in tensile strength but decrease in ductility
(c) decrease in both tensile strength and ductility
(d) increase in both tensile strength and ductility
Ans- b
Ques 24.For good workability of concrete
(a) grading of all-in-aggregate should be continuous
(b) correct quantity of mortar should be present
(c) too much vibration and floating should be avoided
(d) all these
Ans- d
Ques 25. Too prevent bleeding
(a) excess of mortar should be avoided
(b) too much vibration should be avoided
(c) too much floating should be avoided
(d) all these
Ans- d
Ques 26. Yielding of concrete due to sustained stresses, is called
(a) bleeding
(b) segregation
(c) honeycombing
(d) creep
Ans- d
Ques 27. If there is a seepage of absorbed water from cement gel, then it causes
(a) bleeding
(b) segregation
(c) honeycombing
(d) creep
Ans- d
Ques 28. In creep curve, there is/are
(a) only one stage
(b) two stages
(c) three stages
(d) no stages at all
Ans- c
Ques 29. In the primary creep range, rate of creep
(a) remains unaltered
(b) increases with time
(c) decreases with time
(d) none of these
Ans- c
Ques 30. In creep curve, tertiary creep
(a) will always exist
(b) will never exist
(c) may exist
(d) none of these
Ans- c
Ques 31. Presence of tertiary creep depends upon
(a) a decrease in stress
(b) a decrease in strain
(c) an increase in strain
(d) an increase in stress
Ans- d
Ques 32. During hydration, cement gel
(a) increases in volume
(b) decreases in volume
(c) causes segregation
(d) causes bleeding
Ans- a
Ques 33. When there is no water passes between concrete and environment then
(a) drying creep develops
(b) specific creep develops
(c) basic creep develops
(d) both (a) and (c)
Ans- d
Ques 34. Drying creep is
(a) reversible
(b) irreversible
(c) partly reversible
(d) none of these
Ans- c
Ques 35. Basic creep is
(a) reversible
(b) irreversible
(c) partly reversible
(d) none of these
Ans- b
                            By Rk maurya 
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