Free Concrete Technology MCQs with Answers

• A. Decreased, provided compaction is adequate
• B. Increased within the same curing period
• C. Kept equal to the aggregate-cement ratio
• D. Raised until bleeding completely stops

Explanation: For a properly compacted mix, a lower water-cement ratio usually produces higher compressive strength because it leaves fewer capillary…

• A. Downward movement of coarse aggregate
• B. Upward movement of water through the mix
• C. Loss of cement due to surface abrasion
• D. Expansion of aggregate during hydration

Explanation: Bleeding occurs when mixing water rises to the concrete surface because solid particles settle.

• A. To increase the rate of surface drying
• B. To remove entrapped air from the mixture
• C. To maintain moisture for cement hydration
• D. To reduce the cement content near the surface

Explanation: Curing maintains suitable moisture and temperature so cement hydration can continue.

• A. Accelerating admixture
• B. Air-entraining admixture
• C. Expansive admixture
• D. Water-reducing admixture

Explanation: A water-reducing admixture improves workability at a lower water content or increases workability at the same water content.

• A. It reduces paste demand by improving particle packing
• B. It increases the volume of voids between particles
• C. It eliminates the need for cement hydration
• D. It prevents all forms of concrete shrinkage

Explanation: Well-graded aggregate contains particles of different sizes that pack more efficiently.

• A. Bleeding
• B. Segregation
• C. Plastic shrinkage
• D. False setting

Explanation: Segregation is the separation of the constituents of fresh concrete, commonly because of excessive handling, poor grading, or excessive…

• A. Concrete to attain its design strength
• B. Concrete to complete long-term shrinkage
• C. Concrete mixing, placing and compacting
• D. Aggregate particles to reach saturated absorption

Explanation: Initial setting marks the beginning of loss of plasticity, so it indicates the practical period for mixing, placing and compaction.

• A. Lower workability and higher strength
• B. Higher strength and reduced capillary porosity
• C. Lower workability and lower bleeding
• D. Higher workability and lower potential strength

Explanation: Additional water generally improves workability, but it raises the water-cement ratio and leaves more capillary pores after hydration.

• A. Compaction factor test
• B. Le Chatelier test
• C. Vicat soundness test
• D. Los Angeles abrasion test

Explanation: The compaction factor test is useful for low-workability concrete where the slump test may show little discrimination.

• A. Concrete remains fully covered after placement
• B. Evaporation from the surface exceeds bleeding
• C. Aggregate absorption is zero throughout the mix
• D. The final compressive strength is exceeded

Explanation: Plastic shrinkage occurs before concrete has hardened when rapid surface evaporation exceeds the rate at which bleed water reaches the…

• A. Fineness of cement particles
• B. Strength of cement paste
• C. Soundness of cement volume
• D. Setting time of cement paste

Explanation: The Le Chatelier test measures the tendency of cement to undergo harmful expansion after setting.

• A. Tetracalcium aluminoferrite
• B. Dicalcium silicate
• C. Tricalcium aluminate
• D. Tricalcium silicate

Explanation: Tricalcium silicate, or C3S, hydrates relatively quickly and provides much of the strength gained during the early days.

• A. Temporary stiffening that disappears after remixing
• B. Rapid stiffening followed by strong heat evolution
• C. Permanent stiffening caused by cement hydration
• D. Delayed setting caused by excessive aggregate moisture

Explanation: False set is temporary stiffening, usually caused by the reformation of gypsum during grinding or storage.

• A. Contains no water within its pores
• B. Has filled pores but a dry external surface
• C. Has dry pores and a wet external surface
• D. Adds all its absorbed water to the mix

Explanation: A saturated surface-dry aggregate has its internal pores filled with water, while its external surface carries no free water.

• A. Lignosulphonate
• B. Sodium gluconate
• C. Calcium chloride
• D. Air-entraining resin

Explanation: Calcium chloride accelerates cement hydration and reduces setting time.

• A. High content of tricalcium aluminate
• B. Low content of dicalcium silicate
• C. High content of free lime
• D. Low content of tricalcium aluminate

Explanation: Sulphate-resisting cement contains a low proportion of tricalcium aluminate, or C3A.

• A. Provide pressure-relief spaces for freezing water
• B. Increase cement hydration temperature
• C. Eliminate the need for concrete compaction
• D. Increase the density of hardened cement paste

Explanation: Small, closely spaced air bubbles provide relief spaces for water that expands during freezing.

• A. Volume of cement alone
• B. Required volume of fresh concrete
• C. Volume of mixing water
• D. Volume of entrapped air only

Explanation: The absolute volume method proportionates cement, water, aggregates, air and admixtures so that their absolute volumes produce the…

• A. Chemical expansion of hydrated cement
• B. Complete saturation of coarse aggregate pores
• C. A thin water film around moist sand particles
• D. Loss of air from freshly mixed concrete

Explanation: A thin film of moisture around sand particles pushes them apart and increases the apparent volume of the sand.

• A. Excessive hydration of cement
• B. Excessive fineness of cement
• C. Very low temperature during curing
• D. Insufficient compaction of placed concrete

Explanation: Insufficient vibration or compaction leaves voids between coarse aggregate particles and produces a rough, porous surface called…