MCQs on Water Cement Ratio — Page 2
Questions 16–30 — Tap an option to check your answer.
Q16: What is the ideal water-cement ratio to be used while hand mixing?
Difficulty: Easy
Solution:
For hand mixing, the ideal water-cement ratio is 0.5 to 0.6. Hand mixing cannot achieve the same compaction energy as mechanical mixing, so a slightly higher w/c is needed to make the mix workable enough for manual placement and compaction.
Q17: As water cement ratio increases, ……… also increases.
Difficulty: Easy
Solution:
As the water-cement ratio increases, workability increases. More water in the mix reduces friction between particles and makes the mix more fluid, enabling easier placement. However, compressive and tensile strength both decrease with increasing w/c.
Q18: Sand requiring a high water cement ratio, belongs to:
Difficulty: Medium
Solution:
Zone IV sand (very fine sand) requires a high w/c ratio because its extremely large specific surface area demands more water to wet and lubricate all the fine particles. Fine sands have high water demand, increasing the w/c needed for a given workability.
Q19: Internal friction between the ingredients of concrete, is decreased by using
Difficulty: Easy
Solution:
Internal friction in fresh concrete is reduced by using more water (which acts as lubricant) and coarser aggregates (which have lower specific surface area and less particle-to-particle contact). Fine aggregates increase surface area and friction; less water increases friction.
Q20: The gel space ratio of a concrete sample is given as 0.589. What is the theoretical strength (N/mm2) of that concrete sample?
Difficulty: Hard
Solution:
Using Powers’ formula: f’c = 240 × x³ where x = gel-space ratio = 0.589. f’c = 240 × (0.589)³ = 240 × 0.20456 = 49.09 ≈ 49.04 N/mm²
Q21: Under which condition highest water cement ratio is used?
Difficulty: Medium
Solution:
The highest permitted w/c is used for light structural members exposed to alternate wetting and drying. Light sections are not highly loaded, so higher w/c (lower strength) is permissible, but workability is still needed for placing in thin sections.
Q22: The lower water-cement ratio of concrete produces ……………….
Difficulty: Easy
Solution:
All three effects are correct. Lower w/c produces: (a) more density due to fewer capillary pores; (b) smaller creep and shrinkage due to denser paste with less moisture movement; (c) more bond because denser paste has better adhesion to reinforcement and aggregate.
Q23: Strength of concrete is directly proportional to ……………..
Difficulty: Easy
Solution:
Compressive strength is directly proportional to the cement-water ratio (c/w), which is simply the inverse of the water-cement ratio (w/c). Higher cement-water ratio = lower w/c = higher strength, consistent with Abrams’ Law.
Q24: Pick up the correct statement from the following.
Difficulty: Easy
Solution:
All three statements are correct. Too little water makes the mix harsh and unworkable; too much water causes segregation (heavy aggregates sink, lighter water rises) and weakens the concrete.
Q25: The condition not applicable to water cement ratio law is …………….
Difficulty: Medium
Solution:
Testing at any temperature is NOT a valid condition for Abrams’ Law. The law requires testing at a standard temperature (usually 27°C or 20°C) because temperature affects both the rate of hydration and the strength development. All other conditions (moisture, age, size) are valid requirements for the law to hold.
Q26: Pick up the correct statement from the following
Difficulty: Easy
Solution:
All three statements are correct and describe the fundamental role of cement and water in concrete: hydration causes hardening, hardened paste binds aggregates, and cement contributes strength, durability, and water tightness.
Q27: According to Water – Cement Ratio Law, the strength of workable plastic concrete ………….
Difficulty: Medium
Solution:
All three statements correctly describe Abrams’ Law. The law states strength depends on the amount of water (i.e., the w/c ratio), not on the absolute quality or quantity of cement — only the ratio matters, provided the mix is workable.
Q28: For a satisfactory workable concrete with a constant W.C. ratio increase in aggregate cement ratio ……………………..
Difficulty: Medium
Solution:
At constant w/c ratio, increasing the aggregate-cement ratio (A/C) decreases concrete strength. More aggregate per unit cement means less cement paste per unit volume, less bonding material between aggregates, and a leaner mix with lower compressive strength.
Q29: Water cement ratio is generally expressed volume of water required per ………….
Difficulty: Easy
Solution:
Water-cement ratio is conventionally expressed as the volume (litres) of water required per 50 kg bag of cement, which is the standard bag size in India. A w/c of 0.45 means 22.5 litres per 50 kg bag.
Q30: Study the following statement: I. For constant w/c ratio, finer sand decreases the workability. II. Creep is the deformation of concrete under sustained loading. The correct statement(s) is /are:
Difficulty: Medium
Solution:
Both statements are correct. Statement I is true: finer sand has higher specific surface area, requiring more water to maintain workability at constant w/c — meaning at the same w/c, workability drops. Statement II is true: creep is the gradual, time-dependent deformation of concrete under sustained (constant long-term) load.