Free Concrete Technology MCQs with Answers
80 Concrete Technology MCQs from Civil Engineering, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Concrete technology covers cement, aggregates, water and admixtures, including their properties, proportioning and effect on fresh and hardened concrete. It explains workability, water-cement ratio, setting, hydration, strength, durability, curing, mix design and common defects, while distinguishing segregation and bleeding from general loss of workability.
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80 questions · page 2 of 4
21. What is the main chemical process by which cement develops binding properties after water is added?
- A. Hydration of cement compounds
- B. Evaporation of mixing water
- C. Oxidation of aggregate particles
- D. Carbonation of fresh mortar
Explanation: Hydration is the chemical reaction between cement compounds and water. It forms binding products and releases heat, while evaporation…
Correct answer: Hydration of cement compounds- A. Tricalcium silicate
- B. Dicalcium silicate
- C. Tricalcium aluminate
- D. Tetracalcium aluminoferrite
Explanation: Dicalcium silicate hydrates more slowly and contributes substantially to later-age strength.
Correct answer: Dicalcium silicate- A. Very dry and zero-slump
- B. Highly fluid and self-levelling
- C. Plastic and cohesive
- D. Already hardened and set
Explanation: The slump test is commonly used for fresh concrete with plastic consistency.
Correct answer: Plastic and cohesive- A. Higher permeability and lower durability
- B. Lower cement hydration and faster setting
- C. Higher bleeding and lower strength
- D. Lower permeability and higher durability
Explanation: A lower water-cement ratio usually leaves fewer connected capillary pores after hydration.
Correct answer: Lower permeability and higher durability- A. Lost its plasticity and gained substantial rigidity
- B. Just begun to lose its fluidity
- C. Reached its maximum compressive strength
- D. Completed all hydration reactions
Explanation: Final setting marks the stage when the paste has lost plasticity and become sufficiently rigid.
Correct answer: Lost its plasticity and gained substantial rigidity- A. Release water and increase workability
- B. Absorb water and reduce workability
- C. Prevent cement hydration completely
- D. Increase the cement content automatically
Explanation: Dry porous aggregate absorbs part of the mixing water during mixing. The remaining free water decreases, so the concrete may become less…
Correct answer: Absorb water and reduce workability- A. Cause immediate flash set
- B. Increase aggregate absorption
- C. Delay setting of concrete
- D. Remove entrained air completely
Explanation: Retarding admixtures extend the setting time, which is useful in hot weather or during long transport.
Correct answer: Delay setting of concrete- A. 20 MPa
- B. 25 MPa
- C. 30 MPa
- D. 35 MPa
Explanation: In the usual grade notation, the number following M represents the characteristic compressive strength at 28 days in MPa.
Correct answer: 25 MPa- A. Lowers the pore-water alkalinity
- B. Raises the pore-water alkalinity
- C. Increases the cement content
- D. Prevents oxygen from reaching steel
Explanation: Carbonation reacts with alkaline cement products and lowers the pH of the concrete.
Correct answer: Lowers the pore-water alkalinity- A. Internal water-cement ratio
- B. Surface hardness and uniformity
- C. Aggregate absorption capacity
- D. Initial setting time
Explanation: A rebound hammer measures the rebound of a spring-driven mass and mainly indicates surface hardness and relative uniformity.
Correct answer: Surface hardness and uniformity31. Which aggregate property most directly indicates resistance to wear in concrete pavement surfaces?
- A. Aggregate surface texture
- B. Aggregate water absorption
- C. Aggregate abrasion resistance
- D. Aggregate particle shape
Explanation: Abrasion resistance shows how well aggregate withstands rubbing and traffic wear.
Correct answer: Aggregate abrasion resistance- A. Untreated sewage water
- B. Highly saline seawater
- C. Acidic industrial water
- D. Potable drinking water
Explanation: Potable water is generally suitable because it normally contains no harmful concentrations of substances that interfere with cement…
Correct answer: Potable drinking water- A. Tricalcium aluminate
- B. Dicalcium silicate
- C. Tricalcium silicate
- D. Tetracalcium aluminoferrite
Explanation: Tricalcium aluminate, commonly written as C3A, reacts rapidly with water and contributes substantially to heat generation.
Correct answer: Tricalcium aluminate- A. Increased by the aggregate surface moisture
- B. Reduced by the aggregate surface moisture
- C. Kept unchanged in every case
- D. Replaced by additional cement
Explanation: Wet aggregates contribute water to the mix, so the added batch water should be reduced to maintain the intended water-cement ratio.
Correct answer: Reduced by the aggregate surface moisture- A. Delay cement hydration
- B. Increase the cement content
- C. Remove entrapped air voids
- D. Reduce aggregate size
Explanation: Compaction expels entrapped air and brings the concrete into close contact with reinforcement and formwork.
Correct answer: Remove entrapped air voids- A. Resistance to crushing
- B. Cement content
- C. Water absorption limit
- D. Average particle size
Explanation: Fineness modulus is an index of the average coarseness or fineness of an aggregate based on sieve analysis.
Correct answer: Average particle size- A. Creep
- B. Elastic rebound
- C. Bleeding
- D. Segregation
Explanation: Creep is the time-dependent deformation that develops under sustained stress.
Correct answer: Creep- A. Complete elimination of curing
- B. Normal production variation
- C. Reduction of aggregate volume
- D. Increase in setting time
Explanation: The target mean strength exceeds the specified characteristic strength so that normal variations in materials, batching and workmanship do…
Correct answer: Normal production variation- A. Open-air exposure
- B. Dry-air curing
- C. Membrane curing
- D. Repeated heating
Explanation: Membrane curing seals the concrete surface and reduces moisture loss when ponding or continuous sprinkling is impractical.
Correct answer: Membrane curing- A. Curling
- B. Scaling
- C. Crazing
- D. Dusting
Explanation: Dusting is the formation of a weak, powdery surface layer that can result from excess water, poor finishing or inadequate curing.
Correct answer: Dusting