Q1: Which of the following is a limitation of lightweight concrete when compared to conventional type concrete?
Difficulty: Medium
A. Increased permeability
B. Reduced density
C. Enhanced thermal property
D. Higher fire resistance
Correct Answer: A. Increased permeabilitySolution:Lightweight concrete uses porous lightweight aggregates or introduced air voids. Its primary limitation is increased permeability — the porous aggregate structure creates more capillary paths for water ingress, reducing durability. Reduced density (B), enhanced thermal insulation (C), and higher fire resistance (D) are advantages of lightweight concrete, not limitations.
Q2: When calcium sulphate attacks calcium aluminate hydrate present in concrete, it produces:
Difficulty: Hard
A. Asphalt
B. Anthracite
C. Ettringite
D. Calcium hydroxide
Correct Answer: C. EttringiteSolution:When sulphate ions (from calcium sulphate, sodium sulphate, or magnesium sulphate in soil, groundwater, or seawater) react with calcium aluminate hydrate (C₃A hydration products) and calcium hydroxide in concrete, they produce ettringite (calcium trisulphoaluminate, 3CaO·Al₂O₃·3CaSO₄·32H₂O) and gypsum. Ettringite formation is expansive, causing cracking and deterioration.
Q3: Select the correct statements about the UPV test: 1. Used to measure strength of wet concrete. 2. Used to estimate strength of finished concrete elements. 3. It is a non-destructive test.
Difficulty: Medium
A. 1 and 2
B. 2 and 3
C. 1, 2 and 3
D. 1 and 3
Correct Answer: B. 2 and 3Solution:The UPV test is a non-destructive test (statement 3: correct) used to assess the quality and estimate compressive strength of hardened (finished) concrete elements (statement 2: correct). Statement 1 is incorrect — UPV cannot be used on wet/fresh concrete; it requires a solid, hardened medium for the ultrasonic pulse to travel through meaningfully.
Q4: Which of the following tests is NOT used to test aggregate for its abrasion resistance in concrete works?
Difficulty: Medium
A. Dorry abrasion test
B. Deval attrition test
C. Soundness test
D. Los Angeles test
Correct Answer: C. Soundness testSolution:Three standard tests measure aggregate abrasion resistance: Los Angeles Abrasion Test (rotating drum with steel balls, IS 2386 Part 4), Deval Attrition Test (rotating drum without balls), and Dorry Abrasion Test (flat disc rotation). The Soundness Test (IS 2386 Part 5) uses sodium sulphate or magnesium sulphate immersion cycles to measure resistance to weathering and disintegration — not abrasion. It is therefore NOT an abrasion resistance test.
Q5: How does the strength of concrete differ with age of concrete?
Difficulty: Easy
A. Increases
B. Decreases
C. No effect
D. Increases, then decreases
Correct Answer: A. IncreasesSolution:The strength of concrete increases with age as long as moisture and favourable temperature conditions are maintained for continued cement hydration. The rate of strength gain is rapid in the first 7–28 days (OPC reaches ~65% of 28-day strength at 7 days), then slows, eventually approaching an asymptotic limit over years. Concrete does not lose strength with age under normal conditions.
Q6: The increase in the strength of concrete with time is:
Difficulty: Medium
A. Linear
B. Non-Linear
C. Asymptotic
D. All of the above
Correct Answer: B. Non-LinearSolution:The strength gain of concrete with time is non-linear. It is rapid in the first few days (7-day strength ≈ 65% of 28-day), then the rate slows progressively over weeks and months, eventually approaching (but never quite reaching) an asymptotic limit after several years. A non-linear curve — steep initially, then flattening — describes this behaviour. While ‘asymptotic’ describes the long-term behaviour correctly, ‘non-linear’ is the most complete general descriptor.
Q7: Increase in the moisture content in concrete at the time of mixing:
Difficulty: Medium
A. Reduces the strength
B. Increases the strength
C. Does not change the strength
D. None of these
Correct Answer: A. Reduces the strengthSolution:Concrete strength is primarily governed by the water-cement ratio (Abrams’ Law). Adding more water than required for complete hydration increases the w/c ratio. The excess water does not contribute to strength — it occupies space in the paste and evaporates after hardening, leaving behind capillary voids. These voids make the concrete porous, reduce its density, and significantly lower its compressive strength.
Q8: For a given degree of hydration, the effect of increasing water-cement ratio in concrete:
Difficulty: Medium
A. To increase permeability
B. To decrease permeability
C. Does not change permeability
D. None of these
Correct Answer: A. To increase permeabilitySolution:For a given degree of hydration, increasing the w/c ratio means more water was present in the original mix than was consumed by hydration. This excess water occupies capillary pore space in the paste. When it evaporates, it leaves behind interconnected capillary voids. More water = more excess = more voids = higher permeability. Permeability is therefore directly proportional to the w/c ratio.
Q9: Concrete cured at 15°C for 28 days with datum temperature -11°C: what is the maturity (°C·days)?
Difficulty: Hard
A. 112
B. 308
C. 402
D. 728
Correct Answer: D. 728 °C·daysSolution:Maturity M = Σ[Time × (Temperature − Datum Temperature)]. Given: Time = 28 days, Temperature = 15°C, Datum = −11°C. M = 28 × (15 − (−11)) = 28 × (15 + 11) = 28 × 26 = 728 °C·days.
Q10: Which of the following represents the CORRECT expression for maturity (M) of the concrete sample?
Difficulty: Medium
A. M = Σ(Time × Temperature)
B. M = Σ(Time ÷ Temperature)
C. M = Σ(Temperature ÷ Time)
D. M = Σ(Time + Temperature)
Correct Answer: A. M = Σ(Time × Temperature)Solution:The Nurse-Saul maturity expression is M = Σ[Δt × (T − T₀)], where Δt is the time interval, T is the curing temperature, and T₀ is the datum temperature. In simplified form (when datum is taken as 0°C, or the temperature term is taken as the effective temperature above the datum), this reduces to M = Σ(Time × Temperature). The maturity index is therefore the SUM of products of time and temperature intervals.
