Clause 8 covers durability requirements. Clause 8.2 classifies the environment into five exposure conditions — Mild, Moderate, Severe, Very Severe, and Extreme — and specifies the minimum concrete grade, minimum cement content, and maximum water-cement ratio for each. These requirements often govern over structural design requirements.
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Key Requirements
•Engineer must classify the exposure condition before design (Table 3)
•Minimum concrete grade, cement content, and W/C ratio per Table 5 are mandatory — they override structural requirements if more stringent
•For concrete exposed to sulphate attack, use sulphate-resisting cement (IS 12330) or OPC with C3A < 5%
•Maximum cement content shall not exceed 450 kg/m³ (to control shrinkage cracking)
•Use of mineral admixtures (fly ash, GGBS, silica fume) permitted per relevant IS standards
✓Most residential buildings in non-coastal India fall under 'Moderate' exposure — requiring M25 minimum. Many engineers still specify M20, which is technically non-compliant.
✓External surfaces (compound walls, staircases open to rain) should be treated as 'Severe' even if the building is in a non-coastal area.
✓Basements in contact with soil are often 'Moderate' to 'Severe' depending on groundwater sulphate levels. Always test soil/water before classifying.
Common Mistakes
⚠Classifying everything as 'Mild' to use M20 — this violates durability requirements for most external members.
⚠Forgetting the 450 kg/m³ maximum cement content limit — excess cement causes thermal and shrinkage cracks.
⚠Not considering the most aggressive face of a member — a beam exposed to weather on the bottom face should be classified for the external exposure, not the interior.