• DC-2 / FND2: Moderately aggressive ground (lower sulfate risk) → Lower minimum cement content (often ~300–320 kg/m³) and higher maximum w/c ratio (e.g., 0.55).
  • DC-3 / FND3: More aggressive conditions (higher sulfate, wetter, or more reactive soils) → Higher cement content, lower w/c ratio (better impermeability), and stricter cement type requirements for greater sulfate resistance. Both often have similar nominal strength (~30 N/mm²), but FND3 provides upgraded durability. Variants like FND3Z exist for specific mobility or magnesium issues. Higher DC classes generally demand richer, denser mixes or additional protective measures (APMs).