Building Materials (Concrete)

Q.1. 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)

Q.2. 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

Q.3. 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

Q.4. 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

Q.5. 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

Q.6. For determining compressive strength of concrete, size of specimen cube is
(a) 10 cm
(b) 15 cm
(c) 20 cm
(d) 30 cm

Q.7. 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 (IES 1996)

Q.8. Compressive strength of concrete(in N/mm2) is specified at
(a) 270C ± 30C
(b) 28 days age
(c) 90% relative humidity
(d) all these

Q.9. 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

Q.10.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

Answers
1. a
2. d
3. a
4. d
5. c
6. b
7. c
8. d
9. b
10. d

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