CONCRETE

Chloride Content Limit in Concrete

Maximum acid-soluble chloride permitted in concrete to prevent rebar corrosion — per IS 456 Cl. 8.2.5.2 and Table 7.

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Related on InfraLens
CODES
IS 456
Definition

Per IS 456 Cl. 8.2.5.2 + Table 7, max acid-soluble chloride content as % by mass of cement: prestressed concrete = 0.10%; RCC (severe/very severe/extreme exposure) = 0.20%; RCC (mild/moderate exposure) = 0.30%; PCC = 0.40%. Sources: aggregate, water, admixtures, cement. Sea sand and well water near coast are common offenders.

Typical values
Prestressed concrete (max)0.10% by mass of cement
RCC — severe/very severe/extreme0.20% by mass of cement
RCC — mild/moderate0.30% by mass of cement
PCC0.40% by mass of cement
Where used
  • Aggregate acceptance testing (IS 2386 Part 7)
  • Mix design QA
  • Coastal-zone material specification
  • RMC supplier QA gates
Acceptance / threshold
Per IS 456 Cl. 8.2.5.2 — limit chloride sum from all sources (aggregates, water, admixtures, cement) below table value for exposure class.
Site example
Coastal site, severe exposure, M35 RCC: cement 380 kg/m³, max permissible Cl⁻ = 0.20% × 380 = 0.76 kg/m³. Aggregate test shows 0.04% Cl⁻ in sand (sand mass = 700 kg/m³ → 0.28 kg/m³ contribution). Acceptable since total Cl⁻ < 0.76 kg/m³.
Frequently asked
Max chloride in RCC?
Per IS 456 Cl. 8.2.5.2: 0.20% by mass of cement for severe/very severe/extreme exposure; 0.30% for mild/moderate; 0.10% for prestressed; 0.40% for PCC.
Related concrete terms
Concrete Mix Design
Proportioning of cement, water, aggregates per IS 10262
Concrete Grades (M15-M80)
M20=20 N/mm² characteristic strength at 28 days
Water-Cement Ratio (w/c)
Mass of water to mass of cement. 0.40-0.55 typical.
Concrete Cover
Min concrete from rebar to surface (15-50mm per exposure)
Concrete Curing
Min 7 days for OPC, 10 days for PPC, 14 days for sulphate-resistant
Slump Test / Workability
25-150mm slump per application (IS 1199)
Cube Test (Compressive Strength)
150mm cube compressive strength test at 7/28 days (IS 516)
Concrete Admixtures
Plasticizers, accelerators, retarders per IS 9103