Concrete Technology – Achieving low permeability in hardened concrete: Choose the most comprehensive set of measures that reduce ingress of water and aggressive ions.

Introduction:
Permeability governs durability. Lower permeability reduces penetration of chlorides, sulfates, and carbon dioxide, extending service life of reinforced concrete by slowing corrosion and chemical attack.

Given Data / Assumptions:

• Normal-weight concrete with ordinary Portland cement.
• Durability focus (water and ion ingress).
• Site practices influence pore structure.

Concept / Approach:

Permeability is controlled by capillary pore continuity and microcracking. Aggregates, w/c ratio, curing, and compaction each affect pore refinement and connectivity. Best performance comes from combining all good practices.

Step-by-Step Solution:

Verification / Alternative check:

Rapid chloride permeability or sorptivity tests show pronounced improvement when all measures are adopted together rather than one measure alone.

Why Other Options Are Wrong:

Options A–D individually help but are incomplete. The most correct is the combined approach.

Common Pitfalls:

Relying solely on low w/c without curing, or over-vibrating and causing segregation.

Final Answer:

All the above (combined measures)