1. PGBS stands for:
a) Perfectly Graded Blast furnace Slag
b) Pre-Grinded Blast furnace Slag
c) Poly Granule Blast furnace Slag
d) Processed Granulated Blast furnace Slag
Explanation: It is obtained by processing the waste by-product from the iron industry. It is now being used as an alternative to river sand.
2. Coarse aggregates are classified into how many groups?
a) 3
b) 4
c) 6
d) 2
Explanation: The two main groups of coarse aggregates are single-sized aggregates and graded aggregates.
3. How much percent of material which passes through a specific sieve is contained in that single-size aggregate?
a) 50-60%
b) 85-100%
c) 70-90%
d) 80-85%
Explanation: Single-size aggregate contains mostly one sieve sized particle. 85-100% of the particular size should be there, with 0-25% of such aggregate retaining on next lower sieve.
4. Graded aggregate contains particles of size:
a) Single grade
b) 4.75mm
c) Multi grade
d) <80mm
Explanation: It consists of aggregates of more than one single grade. It ideally contains particles of size 4.75mm and above in a proportionate amount.
5. Flaky particles have:
a) Small thickness
b) Elongated sides
c) Sharp edges
d) Rounded edges
Explanation: Flaky particles have a small thickness compared to the dimensions of other parameters that is width and length.
6. Which size coarse aggregate is ideal for use in a concrete mix?
a) Smaller
b) 4.75-10mm
c) Larger
d) 10-20mm
Explanation: Using the largest size will result in a reduction of cement, water and shrinkage in the concrete mix.
7. Elongation index of coarse aggregates is calculated using:
a) E=w1/w2
b) E=w2/w1
c) E=w2-w1
d) E=w2+w1
Explanation: Elongation index is obtained as a percentage. E=w1/w2 where w1 is the weight of particles retained in length gauge and w2 is the weight of test sample.
8.In crushing test on coarse aggregates, what size particle is taken as a sample?
a) Passing 12.5mm IS sieve
b) Retained on 10mm IS sieve
c) Passing 10mm and retained on 4.75mm IS sieve
d) Passing 12.5mm and retained on 10mm IS sieve
Explanation: As per IS code 383, the sample should contain those aggregates which pass through 12.5mm sieve and are retained on 10mm IS sieve.
9. What is the density of undisturbed gravel?
a) 2630-2760 kg/cum
b) 1920-2160 kg/cum
c) 1600 kg/cum
d) 1200 kg/cum
Explanation: 2630-2760 kg/cum is a density of granite. 1600 kg/cum is of loose gravel and 1200 kg/cum is that of brick ballast.
10. What is the symbol used for well graded gravel as per ISC system of classification?
a) WG
b) G
c) GW
d) W
Explanation: Classification of coarse grained soils (ISC system) gives the symbol for well graded gravel as GW. For poorly graded, it is GP.