| S.No. | Checkpoint | IS Requirement | Status |
|---|---|---|---|
| A. MAJOR OXIDE COMPOSITION | |||
| A1 | Silica (SiO2) content measured per IS 4032 gravimetric method Acceptance: OPC: 21-29%; PPC: higher content due to added fly ash; precision ±0.2% | Cl. 4 — SiO2 determination | OK NC NA HOLD |
| A2 | Lime (CaO) content determined via gravimetric or titrimetric method Acceptance: OPC: 60-67%; CaO/SiO2 ratio checked; precision ±0.3% | Cl. 5 — CaO determination | OK NC NA HOLD |
| A3 | Alumina (Al2O3) content measured per flame photometry or gravimetric method Acceptance: OPC: 3-8%; affects clinker phases; precision ±0.2% | Cl. 6 — Al2O3 determination | OK NC NA HOLD |
| A4 | Iron oxide (Fe2O3) content determined per gravimetric method Acceptance: OPC: 2-6%; affects colour and mineralogy; precision ±0.2% | Cl. 7 — Fe2O3 determination | OK NC NA HOLD |
| A5 | Magnesia (MgO) content measured per complexometric titration or AA spectroscopy Acceptance: Maximum 6% for OPC; excess MgO can cause expansion; precision ±0.2% | Cl. 8 — MgO determination | OK NC NA HOLD |
| A6 | Sulfuric anhydride (SO3) content measured per gravimetric or HPLC method Acceptance: Maximum 3% for OPC; important for setting time control; precision ±0.15% | Cl. 9 — SO3 determination | OK NC NA HOLD |
| B. MINOR COMPONENTS & ADDITIVES | |||
| B1 | Potassium oxide (K2O) and sodium oxide (Na2O) measured per flame photometry Acceptance: Total alkalis (Na2O + 0.658×K2O): typically ≤0.6%; relevant for ASR | Cl. 10 — Alkali content | OK NC NA HOLD |
| B2 | Loss on ignition (LOI) determined per thermogravimetric analysis Acceptance: Maximum 5% for OPC; indicates carbonation or water absorption; precision ±0.3% | Cl. 11 — LOI measurement | OK NC NA HOLD |
| B3 | Insoluble residue measured per gravimetric acid digestion method Acceptance: Maximum 1.5% for OPC; indicates unburned fuel or extraneous matter | Cl. 12 — Insoluble residue | OK NC NA HOLD |
| B4 | For PPC/PSC: fly ash/pozzolana content and composition verified if declared Acceptance: Fly ash: max 35%; silica fume: max 10%; composition documented | Cl. 13 — Pozzolanic material assessment | OK NC NA HOLD |
| C. CLINKER PHASE COMPOSITION | |||
| C1 | Tricalcium silicate (C3S) calculated from Bogue equations Acceptance: OPC: 40-65%; affects early and final strength; calculated from major oxides | Cl. 14 — Phase calculation | OK NC NA HOLD |
| C2 | Dicalcium silicate (C2S) calculated and verified Acceptance: OPC: 10-30%; affects long-term strength development; calculated composition | Cl. 14 — Phase calculation | OK NC NA HOLD |
| C3 | Tricalcium aluminate (C3A) calculated per Bogue formula Acceptance: OPC: 0-10%; C3A limits important for sulfate resistance; calculated from oxide data | Cl. 14 — Phase composition | OK NC NA HOLD |
| C4 | Tetracalcium alumino ferrite (C4AF) calculated from oxide composition Acceptance: OPC: 5-12%; affects color and mineralogy; calculated value verified | Cl. 14 — Phase determination | OK NC NA HOLD |