Showing 1–10 of 19 questions
in Concrete Technology
Self-compacting concrete (SCC) must achieve a slump flow of:
A
150-250 mm
B
300-500 mm
C
600-800 mm
D
900-1000 mm
Correct Answer:
C. 600-800 mm
EXPLANATION
SCC requires slump flow between 600-800 mm to flow and compact under its own weight without vibration.
Which of the following is a measure of concrete workability?
A
Slump test
B
Compressive strength test
C
Modulus of elasticity
D
Permeability test
Correct Answer:
A. Slump test
EXPLANATION
Slump test is the most common field test to measure the workability and flow characteristics of fresh concrete.
What is the recommended curing period for concrete in normal conditions?
A
3 days
B
7 days
C
14 days
D
28 days
Correct Answer:
C. 14 days
EXPLANATION
IS 456:2000 recommends minimum 14 days of moist curing for normal Portland cement in normal temperature conditions.
According to Abrams' Law, the relationship between w/c ratio and compressive strength is:
A
Linear positive relationship
B
Inverse/Negative exponential relationship
C
No relationship
D
Directly proportional
Correct Answer:
B. Inverse/Negative exponential relationship
EXPLANATION
Abrams' Law states that compressive strength decreases exponentially with increase in water-cement ratio.
What is the effect of adding admixtures like retarders in concrete?
A
Increases early strength
B
Delays setting time
C
Reduces water requirement
D
Increases workability permanently
Correct Answer:
B. Delays setting time
EXPLANATION
Retarders delay the setting time of concrete, allowing more time for placement and compaction in large structures.
For a M25 grade concrete, what is the approximate 28-day compressive strength?
A
20 MPa
B
25 MPa
C
30 MPa
D
35 MPa
Correct Answer:
B. 25 MPa
EXPLANATION
M25 designation means the concrete will achieve 25 MPa minimum compressive strength at 28 days with 95% probability.
Which chemical compound in cement causes flash setting when exposed to water?
A
C3S (Tricalcium Silicate)
B
C2S (Dicalcium Silicate)
C
C3A (Tricalcium Aluminate)
D
C4AF (Tetracalcium Aluminoferrite)
Correct Answer:
C. C3A (Tricalcium Aluminate)
EXPLANATION
C3A reacts rapidly with water and is responsible for flash setting. Gypsum is added to control this reaction.
What is the typical strength gain pattern of concrete in the first 28 days?
A
Linear growth throughout
B
Rapid growth in first 7 days, then slower
C
Slow initial growth, then rapid after 14 days
D
Constant growth at all stages
Correct Answer:
B. Rapid growth in first 7 days, then slower
EXPLANATION
Concrete gains approximately 40-50% strength in 7 days due to rapid hydration, then strength gain slows down gradually.
Which standard specifies the code of practice for plain and reinforced concrete in India?
A
IS 383:2016
B
IS 456:2000
C
IS 1199:1959
D
IS 12269:2013
Correct Answer:
B. IS 456:2000
EXPLANATION
IS 456:2000 is the Indian Standard for plain and reinforced concrete - Code of Practice.
What is the nominal maximum size of coarse aggregate for concrete beams?
A
10 mm
B
20 mm
C
40 mm
D
80 mm
EXPLANATION
For reinforced concrete beams, nominal maximum coarse aggregate size is typically 20 mm to ensure proper placement around reinforcement.
