| Characteristics | Grade l | Grade II |
| CaO | 52% min | 50%min |
| MgO | 2% max | 3%max |
| Acid insoluble | 2% max | 4% max out of which SO2 should not exceed 1.8% |
| Preferred size | 60 mm, 25 mm not exceed 5% | 6 mm not exceed 10% |