# Concrete Technology Questions and Answers – Strength of Aggregates

This set of Concrete Technology Multiple Choice Questions & Answers (MCQs) focuses on “Strength of Aggregates”.

1. Pick up the most appropriate statement from the following.
a) Bulk density of normal weight aggregate is 1600 kg/m3
b) Bulk density of normal weight aggregate is 2000 kg/m3
c) Bulk density of normal weight aggregate is 1000 kg/m3
d) Bulk density of normal weight aggregate is 1250 kg/m3

Explanation: Bulk density of normal weight aggregate is around 1520 to 1680 kg/m3 and the rest of the options don’t come under that range.

2. The 28 days cube strength of mass concrete using aggregates of maximum size 5 cm for gravity dams should be _________
a) Between 150 to 300 kg/cm2
b) Between 350 to 600 kg/cm2
c) Between 150 to 400 kg/cm2
d) Less than 200 kg/cm2

Explanation: The 28 days cube strength of mass concrete using aggregates of maximum size 5 cm for gravity dams should be less than 200 kg/cm2.

3. The unit weight of heavy weight concrete varies from __________ kg/m3.
a) 1000
b) 2400
c) 2000
d) 1400

Explanation: The unit weight of heavy weight concrete varies from 2400 kg/m3 with sp.gr range from 4.0 to 4.6. (eg: mineral ore sand barite).

4. The use of crushed aggregates may results in 10 to 20% higher compressive strength.
a) True
b) False

Explanation: The use of crushed aggregates may results in 10 to 20% higher compressive strength due to development of stronger aggregate-mortar bond.

5. S.I. unit of bulk density is?
a) kg/l
b) g/ml
c) kg/ml
d) g/l

Explanation: Bulk density of an aggregate is defined as the mass of material in a given volume and expressed in kg/l.
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6. What is void ratio?
a) 1 – (bulk density/apparent sp gr)
b) (bulk density/apparent sp gr) – 1
c) 1 – bulk density/apparent sp gr
d) bulk density/apparent sp gr – 1

Explanation: The empty space between the aggregates particles are termed as voids. And the corresponding ratio will be calculated by the given formula.

7. The average specific gravity of natural aggregate is?
a) 2.7
b) 3
c) 1.5
d) 1

Explanation: The average specific gravity of majority of natural aggregates lies between 2.6 and 2.8.

8. Pick up the most appropriate statement from the following.
a) Sp. Gr. = c/a-b
b) Sp. Gr. = c/(a-b)
c) Sp. Gr. = a-b/c
d) Sp. Gr. = (a-b)/c

Explanation: Specific gravity is the ratio of the density of a substance to the density of a reference substance; equivalently, it is the ratio of the mass of a substance to the mass of a reference substance for the same given volume.

9. The ratio of the mass of the aggregate dried in an oven at ___________ for 24 hours to the mass of the water occupying a volume equal to that of solid.
a) 100-110oC
b) 150-180oC
c) 100oC
d) 1500oC

Explanation: First sieve the sample aggregate, aggregate passing 12.5mm sieve and retaining 10mm sieve is oven dries at 100-110oC for 3-4 hrs.

10. Aggregate abrasion value is determined by__________
a) Aggregates crushing strength
b) Los Angeles abrasion test
c) Aggregates Impact value test
d) Ten percent fine test

Explanation: Aggregate abrasion value is determined by Los Angeles abrasion test as described in IS: 2386.

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