Concrete technology — effects of poor mixing A badly mixed cement concrete most commonly results in which of the following defects?

Introduction / Context:
Concrete quality depends on proportioning, mixing, placing, and curing. Poor mixing introduces variability that manifests as visible and structural defects. Recognizing these helps site engineers correct practices before strength and durability are compromised.

Given Data / Assumptions:

• Conventional Portland cement concrete for structural or masonry use.
• Improper mixing leads to non-uniform paste distribution and inconsistent water content.
• No admixtures specifically mitigating these defects are assumed.

Concept / Approach:
Segregation is the separation of coarse aggregate from mortar due to excess water or improper handling. Bleeding is upward migration of water, leaving a weak, laitance-prone surface. Honeycombing arises from poor compaction and non-uniform mortar, leaving voids. Inadequate mixing aggravates all three by creating paste-rich and paste-poor pockets that resist consolidation.

Step-by-Step Solution:
Link poor mixing to non-uniform water–cement–aggregate distribution.Explain symptom pathways: excess free water → bleeding; segregated coarse aggregate → voids; insufficient mortar coating → honeycombing.Conclude that all listed defects are promoted by bad mixing.

Verification / Alternative check:
Core tests from defective regions often show lower density and rebound numbers, consistent with honeycombing and segregation effects.

Why Other Options Are Wrong:
Each individual defect can occur, but they are not mutually exclusive; the comprehensive option reflects the range of consequences.

Common Pitfalls:
Attempting to correct segregation solely by over-vibration; this can worsen bleeding. Ignoring proper sequencing and mix time contributes to persistent defects.

Final Answer:
All of the above