Compaction quality — effects of non-uniform compaction on concrete Non-uniform compaction during placement and vibration of concrete may result in which of the following problems?

Introduction / Context:
Compaction expels entrapped air and consolidates the matrix around reinforcement. Inadequate or uneven vibration compromises density and uniformity, impacting both strength and service life of the structure.

Given Data / Assumptions:

• Normal vibrated concrete under site conditions.
• Variations in operator technique or equipment reach.
• Standard cover and reinforcement congestion.

Concept / Approach:

When areas are under-vibrated, voids remain and paste does not fully envelop aggregates and bars, leading to honeycombing and weaker interfaces. Over-vibration may cause segregation, yielding non-homogeneous layers. Both conditions reduce compressive strength and durability by increasing permeability and creating stress concentrators.

Step-by-Step Solution:

Verification / Alternative check:

Core tests and petrographic examination of defective zones typically reveal entrapped air pockets and paste–aggregate separation.

Why Other Options Are Wrong:

• Each individual effect occurs; therefore the inclusive option “All of the above” best represents the outcome.

Common Pitfalls:

• Allowing long delays between lifts causing cold joints; consistent compaction is still needed across lifts.

Final Answer:

All of the above.