--- title: "Cement manufacture with flow diagram" subject: "Civil Engineering Materials" chapter: 5 key: "semester_3/civil_engineering_materials:cement-manufacture-flow-diagram" source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/cement-manufacture-flow-diagram site: BCT Engineering --- # Cement manufacture with flow diagram Civil Engineering Materials · Chapter 5: Cement - Asked in: 2073 Shrawan, 5 marks; 2079 Bhadra, 4 marks; 2069 Chaitra, 2 marks; 2074 Chaitra, 1 marks; 2074 Asoj, 1 marks (asked 5 times) - Video: [How Cement Is Made In Factories?](https://www.youtube.com/watch?v=RcrMBYsB93E) — Engineering World - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/cement-manufacture-flow-diagram - Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-5 ## Question Describe the manufacturing process of cement (53 grade OPC) with the help of a suitable flow diagram. ## Short answer Raw materials are crushed, dry-ground, blended, preheated in cyclones, and burned at 1400-1500°C to clinker. Clinker is cooled, ground with 3-5% gypsum to high fineness, yielding 53 grade OPC with 28-day strength ≥53 MPa. ## Answer Cement is a fine grey powder made by burning a mixture of calcareous (limestone) and argillaceous (clay) materials into clinker and grinding it with gypsum. 53 grade OPC (IS 12269) is made by the **dry process** in modern plants, because this process gives a closely controlled, fuel-efficient kiln feed. #### Raw materials - **Calcareous:** limestone, chalk, marl (supplies CaO, about 60-65% of the cement). - **Argillaceous:** clay, shale (supplies SiO₂, Al₂O₃, Fe₂O₃). - **Correctives:** bauxite, iron ore, silica sand (to adjust the composition). - **Gypsum** (added after burning) to control setting. #### Flow diagram ```text Limestone + Clay (+ correctives) | Crushing & Pre-blending | Raw mill (dry grinding to fine powder) | Blending / Homogenising silo | Preheater (cyclones, 800-900 °C) | Rotary kiln (1400-1500 °C) -> CLINKER | Clinker cooler | Clinker + Gypsum (3-5%) -> Cement mill | Cement silo | Packing (50 kg bags) / Bulk dispatch ``` #### Steps 1. **Quarrying and crushing:** limestone and clay are quarried and crushed to about 25 mm. 2. **Proportioning and dry grinding:** the materials are mixed in the right ratio (about 75-80% limestone, 20-25% clay) and ground in the raw mill to a fine, dry powder called raw meal (moisture below 1%). 3. **Blending:** the raw meal is homogenised with compressed air in silos so that its chemical composition is uniform (the lime saturation factor and the silica and alumina moduli are checked). 4. **Preheating:** hot kiln gases heat the meal in cyclone preheaters, and calcination begins (CaCO₃ → CaO + CO₂). 5. **Burning:** in the rotary kiln (inclined at 3-4%, rotating at 1-3 rpm) the meal passes through the drying, calcination and clinkering zones. At about 1450 °C, partial fusion forms nodules of **clinker** (C₃S, C₂S, C₃A, C₄AF). 6. **Cooling:** the clinker is cooled rapidly in a grate cooler. 7. **Grinding:** the clinker with 3-5% gypsum is ground in a ball mill to a fineness of at least 225 m²/kg (Blaine). 8. **Storage and packing:** the cement is stored in silos and packed in 50 kg bags. 53 grade cement has more C₃S and is ground finer, giving a 28-day compressive strength of at least 53 MPa. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Why is 53 grade OPC made in modern plants by the dry process? A. Wet slurry is required for fineness B. It avoids using a kiln C. It needs finely controlled, fuel-efficient kiln feed D. It needs no grinding Answer: C. The dry process gives a controlled raw meal and uses less fuel, so it is the modern standard. (Key point: Dry process) 2. What is the correct order in the dry process? A. Kiln, raw mill, cooler, blending, preheater B. Cement mill, kiln, raw mill, cooler C. Preheater, raw mill, cooler, kiln D. Raw mill, blending silo, preheater, rotary kiln, cooler, cement mill Answer: D. Raw meal is ground, blended, preheated, burnt in the kiln, cooled and then ground with gypsum. (Key point: Sequence) 3. What happens in the kiln burning zone at about 1450 C? A. Partial fusion forms clinker nodules B. Only drying of raw meal C. Grinding with gypsum D. Cement is bagged Answer: A. At about 1450 C partial fusion forms clinker nodules of C3S, C2S, C3A and C4AF. (Key point: Clinkering zone) 4. At which stage and in what amount is gypsum added? A. 10-15% in the raw mill B. 3-5% with clinker in the cement mill C. 3-5% in the kiln D. None; it is added on site Answer: B. Clinker is ground with 3-5% gypsum to control setting. (Key point: Gypsum grinding) ## Related in Civil Engineering Materials - [7 and 28 day strength of 53 grade OPC](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aopc-53-grade-strength) — Civil Engineering Materials, chapter 5 - [Wet process of cement manufacture](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Acement-wet-process-flow-diagram) — Civil Engineering Materials, chapter 5, asked 4× - [Dry process of cement manufacture](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Acement-dry-process-flow-chart) — Civil Engineering Materials, chapter 5 - [Manufacturing process of bricks](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Amanufacturing-process-of-bricks) — Civil Engineering Materials, chapter 3, asked 4× - [Meaning of grade 43 cement](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Agrade-43-cement) — Civil Engineering Materials, chapter 5 - [Manufacturing process of lime](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Amanufacture-of-lime) — Civil Engineering Materials, chapter 4, asked 2× ## Related in other subjects - [Grade of cement; Bogue's compounds](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Agrade-of-cement-bogue) — Concrete Technology and Masonry Structure, chapter 1 - [Preparing cement mortar by manual process](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Amortar-prep-manual) — Building Technology, chapter 3, asked 2× - [OPC versus PPC](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aopc-vs-ppc) — Concrete Technology and Masonry Structure, chapter 1 - [Mass haul diagram and soil cement base](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Amass-haul-soil-cement-base-construction) — Transportation Engineering II, chapter 3