Durability of RCC in Marine Exposure For reinforced concrete directly in sea water or exposed to severe marine conditions, which minimum concrete grade should be used for durability and strength?

Introduction / Context:
Marine environments impose severe durability demands on reinforced concrete due to chloride ingress, wetting and drying cycles, and sulphate action. Codes mandate a minimum concrete grade to limit permeability and protect reinforcement.

Given Data / Assumptions:

• Exposure: structures in sea water or directly exposed to sea spray and saline atmosphere.
• Performance target: lower permeability and adequate cover to resist corrosion.
• Concrete grades considered: M10, M15, M20, M30.

Concept / Approach:

Higher characteristic strength generally corresponds to a denser matrix, reduced capillary porosity, and improved durability. Codes for severe exposure prescribe not just cover and cement type, but also minimum grade.

Step-by-Step Solution:

Verification / Alternative check:

Durability tables in standard practice align with M30 or higher along with adequate cover, low water–cement ratio, and suitable cementitious materials to resist chlorides.

Why Other Options Are Wrong:

• M10 and M15: Intended for lean or non-structural uses; too porous for marine RCC.
• M20: Common for general RCC but inadequate for severe chloride exposure without special measures.

Common Pitfalls:

Assuming strength alone ensures durability. In practice, cover, w/c ratio, curing, and supplementary cementitious materials also matter, but the minimum grade M30 remains a baseline requirement.

Final Answer:

M 30