Concrete Compaction – benefits achieved by proper compaction Which properties of hardened concrete are improved by adequate compaction during placement?

Introduction / Context:
Compaction expels entrapped air from freshly placed concrete and helps the paste fully surround aggregates and reinforcement. Poor compaction leads to honeycombing, pathways for ingress, and loss of section, all of which degrade performance.

Given Data / Assumptions:

• Concrete placed with internal or external vibrators as appropriate.
• Proper mix design and slump for the element being cast.
• Vibration applied just enough to remove air without segregation.

Concept / Approach:
Reducing voids raises unit weight (density). With fewer voids, the load-bearing solid skeleton increases, hence compressive strength rises. Denser, well-bonded concrete is less permeable, improving durability by resisting chloride ingress, carbonation, and freeze–thaw cycles.

Step-by-Step Solution:
Adequate compaction → less entrapped air → higher density.Higher density + improved paste–aggregate bond → higher compressive strength.Lower permeability and better cover quality → improved durability.

Verification / Alternative check:
Cube strength comparisons between poorly compacted and well-compacted specimens show significant strength gains when air voids are minimized (each 1% air can reduce strength by roughly 5% in ordinary concretes).

Why Other Options Are Wrong:

• Choosing single properties (a–c) ignores the holistic improvement; all are positively affected.
• “None” conflicts with well-established effects of compaction.

Common Pitfalls:
Over-vibration causing segregation or loss of entrained air in air-entrained mixes; under-vibration leaving honeycombs. Match vibrator type and duration to section thickness and reinforcement congestion.

Final Answer:
All of the above