Class: Senior Secondary School 1 (SS 1)
Term: 3rd Term
Week: 3
Age: 15 years
Duration: 45 minutes
Subject: Block Laying, Brick Laying and Concrete Work
Curriculum Theme: Entrepreneurship (Trade Subjects)
Previous Lesson: Definition and Types of Cement.
Topic: MANUFACTURING PROCESS OF PORTLAND CEMENT
Subject Matter: raw materials for cement, stages in cement manufacture, processing of Portland cement

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

List the raw materials used in the manufacture of Portland cement.
Outline the major stages involved in the dry process of Portland cement manufacturing.
Describe the function of key equipment used in cement production.

Affective Domain:

Appreciate the industrial importance of Portland cement.
Show interest in the processes involved in manufacturing building materials.

Psychomotor Domain:

Sketch a simple flow chart illustrating the cement manufacturing process.
Identify samples of raw materials for cement production.

Work collaboratively with peers to discuss the cement manufacturing process.

Reference Materials

The following resources were used in planning this lesson:

Senior Secondary Education Curriculum for Block Laying, Brick Laying and Concrete Work.
State Unified Scheme of Work for Block Laying, Brick Laying and Concrete Work.
Basic Building Construction by B.N. Akinkugbe.
Building Construction for Senior Secondary Schools by J.O. Agunbiade.

Instructional Materials

The teacher will teach this lesson with the aid of:

Charts showing the Portland cement manufacturing process.
Diagrams illustrating key machinery (e.g., rotary kiln, crushers).
Samples of raw materials like limestone, clay, gypsum (if available).
A small bag or sample of Portland cement.

Rationale for the Lesson

Understanding the manufacturing process of Portland cement helps pupils to appreciate how a fundamental building material is made. This knowledge is important for proper handling and usage of cement in construction, contributing to the quality and durability of structures.

Prerequisite/Previous Knowledge

Pupils are expected to have basic knowledge of common building materials and their uses, especially the role of cement in construction from previous lessons or general observations.

Lesson Content/Board Summary

MANUFACTURING PROCESS OF PORTLAND CEMENT

Raw Materials for Portland Cement Production

Portland cement is primarily manufactured from calcareous materials (rich in calcium carbonate) and argillaceous materials (rich in silica and alumina). These materials are carefully proportioned and processed.

The following are the main raw materials:

Limestone (Calcium Carbonate – CaCO₃): This is the main source of calcium, forming about 70-80% of the raw mix.
Clay/Shale (Silica – SiO₂, Alumina – Al₂O₃, Iron Oxide – Fe₂O₃): Provides silica, alumina, and iron oxide.
Sand (Silica – SiO₂): Used to adjust the silica content if needed.
Iron Ore (Iron Oxide – Fe₂O₃): Used to adjust the iron content.
Gypsum (Hydrated Calcium Sulphate – CaSO₄·2H₂O): Added to clinker in the final grinding stage to control the setting time of cement.

Stages in Portland Cement Manufacturing Process (Dry Process)

The dry process is a common method for manufacturing Portland cement. It involves several distinct stages:

The major stages are:

1. Quarrying and Crushing of Raw Materials:
Limestone and clay are extracted from quarries. Large rocks are crushed into smaller pieces (about 1.5 cm to 2 cm) using primary and secondary crushers.
2. Grinding and Proportioning of Raw Mix:
The crushed raw materials (limestone, clay, sand, iron ore) are ground into a fine powder, called ‘raw meal’, in ball mills. They are then accurately weighed and mixed in correct proportions to achieve the desired chemical composition.
3. Pre-heating and Calcination:
The raw meal is fed into pre-heater towers where hot gases from the kiln heat it. This removes moisture and initiates calcination, where limestone (CaCO₃) decomposes into lime (CaO) and carbon dioxide (CO₂).
4. Clinkering in Rotary Kiln:
The pre-heated raw meal enters a large, inclined rotating furnace called a rotary kiln, which operates at very high temperatures (1400-1500°C). Here, the raw materials react chemically to form ‘clinker’, which are dark grey, hard, nodular pellets (1-25 mm in diameter).
5. Cooling of Clinker:
The hot clinker discharged from the kiln is rapidly cooled using air. This rapid cooling helps to preserve the desired mineral composition of the clinker.
6. Grinding of Clinker with Gypsum:
The cooled clinker is ground into a very fine powder in ball mills, along with a small percentage (typically 3-5%) of gypsum. Gypsum is added to regulate the setting time of the final cement product.
7. Packaging and Storage:
The finely ground cement is then conveyed to silos for storage before being packed into bags (e.g., 50 kg bags) or loaded into bulk tankers for distribution.

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils and asks them to mention common building materials they know. The teacher then specifically asks about cement and its uses, linking it to the topic of how it is made.
Pupils’ Activity: Pupils respond to questions by mentioning building materials like sand, gravel, water, and cement, and state uses of cement such as making concrete and mortar.
Learning Point: Pupils recall prior knowledge of building materials and are introduced to the lesson topic.

Step 2: Presentation of Raw Materials

Time: 8 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher presents samples (if available) or charts of raw materials like limestone, clay, and gypsum. The teacher explains the primary role of each material in cement production.
Pupils’ Activity: Pupils observe the samples/charts, listen attentively, and note down the raw materials.
Learning Point: Pupils identify and understand the function of key raw materials for Portland cement.

Step 3: Explanation of Crushing and Grinding

Time: 7 minutes
Teaching Skill: Explanation/Illustration
Teacher’s Activity: The teacher explains the initial stages of crushing large raw materials into smaller pieces and then grinding them into a fine raw meal. The teacher emphasizes the importance of precise proportioning.
Pupils’ Activity: Pupils listen and ask questions for clarification regarding the initial processing steps.
Learning Point: Pupils understand the preparation of raw materials before kiln processing.

Step 4: Explanation of Kiln Processing (Pre-heating, Clinkering)

Time: 10 minutes
Teaching Skill: Illustration/Discussion
Teacher’s Activity: Using diagrams or charts, the teacher explains the pre-heating process, the calcination, and the critical clinkering stage inside the rotary kiln, highlighting the high temperatures and chemical reactions involved in forming clinker.
Pupils’ Activity: Pupils observe the diagrams, listen to the explanation, and ask questions about the kiln process and clinker formation.
Learning Point: Pupils grasp the central role of the rotary kiln in transforming raw materials into clinker.

Step 5: Explanation of Cooling, Grinding with Gypsum, and Packaging

Time: 7 minutes
Teaching Skill: Explanation/Summarization
Teacher’s Activity: The teacher explains the cooling of clinker, the final grinding process where gypsum is added, and the reasons for adding gypsum. The teacher concludes with the packaging and storage of the finished cement.
Pupils’ Activity: Pupils listen and understand the final steps that lead to the usable cement product.
Learning Point: Pupils understand how clinker is processed into final cement and the role of gypsum.

Step 6: Class Activity/Discussion

Time: 3 minutes
Teaching Skill: Group Work/Collaboration
Teacher’s Activity: The teacher divides pupils into small groups and asks them to briefly discuss and list the main stages of cement production they have learned.
Pupils’ Activity: Pupils discuss in groups and share their lists with the class.
Learning Point: Pupils consolidate their understanding through peer discussion and active recall.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

Mention three primary raw materials used in the manufacture of Portland cement.
Outline any four major stages in the dry process of cement manufacturing.
What is the function of gypsum in the final stage of cement production?
Briefly describe what happens in the rotary kiln during cement manufacturing.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 5 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key stages of Portland cement manufacturing and reiterates its importance in the construction industry. The teacher then gives pupils an assignment to draw a flow chart of the cement manufacturing process.
Pupils’ Activity: Pupils listen to the summary and copy down the assignment.
Learning Point: Pupils reinforce their understanding and are given an opportunity for further practice.

Lesson Keywords

Portland Cement – A hydraulic cement that hardens when combined with water, forming a strong, durable material.
Raw Materials – The basic substances (like limestone and clay) used to produce cement.
Limestone – A calcareous rock, the main source of calcium in cement production.
Clay – An argillaceous material, providing silica, alumina, and iron oxide.
Rotary Kiln – A large, rotating furnace used to heat raw materials to high temperatures to form clinker.
Clinker – Hard, nodular pellets formed in the rotary kiln, which are then ground to make cement.
Gypsum – Calcium sulphate added to clinker during grinding to control the setting time of cement.
Calcination – The process of heating a substance to a high temperature to cause decomposition, such as limestone into lime and carbon dioxide.

Differentiation

For pupils who grasp concepts quickly, the teacher can ask them to research different types of cement (e.g., rapid hardening cement, low heat cement) and their specific uses. For pupils needing more support, the teacher can provide simplified diagrams or a pre-filled worksheet for labeling the stages of cement production.

Note for teachers using this lesson plan

Teachers should ensure that diagrams and charts used are clear and easy for pupils to understand. If real samples of raw materials are unavailable, clear pictures or videos can be used as alternatives. Emphasize safety precautions in handling any materials, even samples. Encourage pupils to relate the manufacturing process to the final properties and uses of cement in construction.