Q1: Which of the following conditions followed in making concrete reduces the workability of concrete?
Difficulty: Easy
A. Use of superplasticizers
B. Higher aggregate-cement ratio in concrete
C. Use of round aggregates
D. Higher water-cement ratio in concrete
Correct Answer: B. Higher aggregate-cement ratio in concrete
Solution:
A higher aggregate-cement ratio means more aggregate per unit of cement paste. The paste available to lubricate and coat aggregate surfaces decreases, causing increased inter-particle friction and reduced workability.
Q2: Which characteristic of fine aggregates indicates their ability to retain water and affects the workability of concrete or mortar mix?
Difficulty: Easy
A. Particle size distribution
B. Specific gravity
C. Fineness modulus
D. Water absorption
Correct Answer: D. Water absorption
Solution:
Water absorption of fine aggregates indicates how much water the aggregate particles can absorb from the mixing water. High water absorption reduces the effective free water in the mix, lowering workability.
Q3: Due to segregation of well-mixed concrete, -
Difficulty: Easy
A. the workability of concrete decreases
B. the durability of concrete increases
C. the strength of concrete increases
D. the permeability of concrete decreases
Correct Answer: A. the workability of concrete decreases
Solution:
Segregation disrupts the homogeneous distribution of materials in concrete. Once segregation occurs, the remaining mix loses its uniform paste-aggregate balance, which reduces its ability to flow and be compacted — lowering workability.
Q4: Consider the below statements with respect to cement concrete and identify the correct statement(s).
Difficulty: Medium
A. Only i
B. Only ii
C. i and iii
D. i and ii
Correct Answer: A. Only i
Solution:
Only statement i is correct. Aggregate size and shape do significantly influence workability. Statement ii is false (higher w/c decreases strength per Abrams' Law). Statement iii is false (maturity depends on both time AND temperature).
Q5: Which of the following types of soil have excellent workability as a construction material?
Difficulty: Easy
A. Well graded gravel
B. Silty sand
C. Silty gravel
D. Clayey sand
Correct Answer: A. Well graded gravel
Solution:
Well-graded gravel (GW in USCS) has excellent workability as a construction material for earthworks because it is easy to compact, drains freely, provides good shear strength, and does not swell or shrink excessively.
Q6: Experimental water absorption tests are done on fine aggregates to find the:
Difficulty: Medium
A. Only (i) Water holding capacity, (ii) Strength of material, and (iii) Quality of material
B. Both (i) and (ii)
C. Only (i)
D. (i), (ii), (iii), and (iv) Shape of aggregates
Correct Answer: A. Only (i), (ii) and (iii)
Solution:
Water absorption tests on fine aggregates provide information on water holding capacity (i), indirectly indicate strength/quality (ii, iii) through porosity, but do NOT indicate shape (iv). Shape is determined by flakiness index and elongation index tests.
Q7: The recommended slump range (mm) as per IS 456:2000, for hand placed pavement quality concrete is:
Difficulty: Medium
A. 50 - 100
B. 100 - 150
C. 75 - 100
D. 25 - 75
Correct Answer: D. 25 - 75
Solution:
IS 456:2000 specifies a slump of 25-75 mm for pavement quality concrete placed by hand. Pavement concrete needs to be relatively stiff (low slump) to resist deformation under finishing and traffic loads.
Q8: According to IS: 5515, the distance between the bottom of the lower hopper and the top of the cylinder in the Compacting Factor Apparatus is:
Difficulty: Hard
A. 22.9 cm
B. 25.4 cm
C. 12.7 cm
D. 20.0 cm
Correct Answer: D. 20.0 cm
Solution:
Per IS 5515, in the Compacting Factor Apparatus, the distance between the bottom of the lower hopper and the top of the cylinder is 20.3 cm ≈ 20.0 cm (approximately 8 inches in the original British standard).
Q9: Two statements: 1: As the compaction factor increases, slump decreases. 2: Slump test helps in qualitatively understand the setting time of concrete.
Difficulty: Medium
A. Both Statement 1 and Statement 2 are true
B. Statement 1 is true and Statement 2 is false
C. Statement 1 and Statement 2 are false
D. Statement 1 is false and Statement 2 is true
Correct Answer: C. Statement 1 and Statement 2 are false
Solution:
Both statements are false. Statement 1 is false: as compaction factor increases, slump also increases (both indicate higher workability). Statement 2 is false: slump test measures consistency/workability, not setting time (setting time is measured by the Vicat needle test).
Q10: What is the height of a slump cone mould used for testing the workability of the concrete?
Difficulty: Easy
A. 20 cm
B. 10 cm
C. 30 cm
D. 25 cm
Correct Answer: C. 30 cm
Solution:
The slump cone has a height of 30 cm (300 mm). The full dimensions are: top diameter = 10 cm, bottom diameter = 20 cm, height = 30 cm. These are standard dimensions per IS 1199.
Q11: According to IS 456-2000, what is the slump of a medium degree of workability of concrete if placed in heavily reinforced sections like slabs, beams, walls, columns?
Difficulty: Medium
A. 10 - 25 mm
B. 25 - 50 mm
C. 0 - 10 mm
D. 50 - 100 mm
Correct Answer: D. 50 - 100 mm
Solution:
IS 456:2000 specifies a slump of 50-100 mm for concrete placed in heavily reinforced sections (slabs, beams, walls, columns) requiring medium degree of workability. The higher range helps concrete flow through reinforcement bars.
Q12: Which of the following properties of concrete is determined using a compaction factor test?
Difficulty: Easy
A. Density of concrete
B. Porosity of concrete
C. Strength of concrete
D. Workability of concrete
Correct Answer: D. Workability of concrete
Solution:
The compaction factor test (IS 1199) is specifically designed to measure the workability of fresh concrete, particularly for mixes of low to medium workability where the slump test is less sensitive.
Q13: Which of the following increases the workability of concrete?
Difficulty: Medium
A. Increasing aggregate-cement ratio
B. Decreasing the water-cement ratio
C. Using angular aggregates instead of round aggregates
D. Increasing the aggregate size without any change in the mix of concrete
Correct Answer: D. Increasing the aggregate size without any change in the mix of concrete
Solution:
Increasing the aggregate size (at constant cement, water, and fine aggregate content) reduces total aggregate specific surface area. Less surface area means less water is needed to coat all surfaces, leaving more free water available for lubrication — increasing workability.
Q14: Which of the following decreases the workability of concrete?
Difficulty: Easy
A. Angular aggregates
B. Well graded aggregates
C. Air entraining admixture
D. Rounded aggregates
Correct Answer: A. Angular aggregates
Solution:
Angular aggregates have rough, irregular surfaces that create more inter-particle friction than smooth rounded aggregates. This friction resists the flow of concrete, reducing workability. All other options (well-graded, air-entraining, rounded) improve workability.
Q15: Which statements are correct about aggregate shape's influence on strength and workability?
Difficulty: Medium
A. S2 and S3
B. S1 and S2
C. S1 and S4
D. S3 and S4
Correct Answer: C. S1 and S4
Solution:
S1 is correct: rounded aggregates have smooth surfaces giving high workability but weaker mechanical bond giving lower strength. S4 is correct: angular aggregates have rough surfaces giving low workability but strong mechanical interlock giving high strength.
