Class: Senior Secondary School 1 (SS 1)
Term: 2nd Term
Week: 10
Age: 15 years
Duration: 45 minutes
Subject: Block Laying, Brick Laying and Concrete Work
Curriculum Theme: Entrepreneurship (Trade Subjects)
Previous Lesson: Definition and Components of Concrete.
Topic: CONCRETE MIXING AND AGGREGATES
Subject Matter: coarse aggregate, fine aggregate, mixing proportion of concrete

Specific Objectives

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

Cognitive Domain:

Define concrete and aggregates.
Identify two types of aggregates.
State common mixing proportions for concrete.

Affective Domain:

Appreciate the importance of correct aggregate selection.
Value accurate mixing proportions for concrete strength.
Participate actively in discussions about concrete materials.

Psychomotor Domain:

Distinguish between coarse and fine aggregates.
Demonstrate the basic concept of concrete mixing.
Prepare materials for concrete mixing according to given proportions.

Collaborate with peers in identifying aggregate types.
Share ideas on the uses of different concrete mixes.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Basic Technology (JSS 1-3) / Trade Subjects (SS 1-3).
State Unified Scheme of Work for Senior Secondary School 1 (SS 1) – Block Laying, Brick Laying and Concrete Work.
Block Laying, Brick Laying and Concrete Work for Senior Secondary Schools by A.B. Olalere.
Relevant charts showing concrete mixing ratios.

Instructional Materials

The teacher will teach this lesson with the aid of:

Samples of cement, fine aggregate (sand), and coarse aggregate (gravel/crushed stone).
Water.
Measuring box/bucket.
Shovel.
Chart showing concrete mixing ratios.

Rationale for the Lesson

Understanding concrete mixing and aggregates helps pupils learn how to produce strong and durable concrete. This knowledge is important for practical applications in construction, enabling them to make informed decisions about building materials and processes in their daily lives and future careers.

Prerequisite/Previous Knowledge

Pupils should have prior knowledge of basic building materials, common hand tools used in construction, and safety precautions on a construction site.

Lesson Content/Board Summary

CONCRETE MIXING AND AGGREGATES

Definition of Concrete

Concrete is a composite construction material made from a mixture of cement, aggregates (fine and coarse), and water, which hardens over time to form a strong, stone-like mass.

Aggregates

Aggregates are granular materials, such as sand, gravel, or crushed stone, that are mixed with cement and water to form concrete. They provide bulk, strength, and stability to the concrete.

The following are the two main types of aggregates:

Coarse Aggregate: These are larger particles, typically gravel or crushed stone, with sizes generally ranging from 5mm upwards. They provide the main body and strength to the concrete.
Fine Aggregate: These are smaller particles, primarily sand, with sizes generally ranging from 0.075mm to 4.75mm. Fine aggregates fill the voids between coarse aggregates and help in achieving a smooth finish.

Mixing Proportion of Concrete

The mixing proportion of concrete refers to the ratio of cement, fine aggregate, and coarse aggregate, along with the amount of water, used to achieve desired strength, durability, and workability for a specific purpose.

The following are common concrete mixing ratios (Cement : Sand : Gravel):

1:2:4: This ratio is typically used for structural concrete, such as beams, columns, slabs, and foundations, where high strength is required.
1:3:6: This ratio is suitable for mass concrete work, such as non-structural foundations, blinding, or where moderate strength is sufficient.
Water-Cement Ratio: The amount of water used is also important. Too much water weakens the concrete, while too little makes it difficult to work with. A correct water-cement ratio ensures proper hydration and strength.

Steps in Manual Concrete Mixing

The following are the basic steps for manual mixing of concrete:

Measure the required quantities of coarse aggregate, fine aggregate, and cement according to the chosen mix ratio.
Spread the coarse aggregate on a clean, hard surface (e.g., concrete slab or mixing board).
Spread the fine aggregate evenly over the coarse aggregate.
Spread the cement evenly over the fine aggregate.
Turn the dry mixture with a shovel until a uniform colour is achieved, indicating thorough mixing of the dry ingredients.
Form a crater (hollow) in the centre of the dry mix.
Pour the measured amount of water gradually into the crater.
Turn the mixture again, working from the outside towards the centre, until a uniform, workable consistency is achieved.

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 introduces the topic by asking pupils what they think concrete is made of and where it is used in building construction. The teacher then explains that today’s lesson will focus on the main components of concrete and how they are mixed.
Pupils’ Activity: Pupils respond to the questions and listen attentively.
Learning Point: Pupils are introduced to the topic and relate it to prior knowledge.

Step 2: Explanation of Aggregates

Time: 8 minutes
Teaching Skill: Explanation/Illustration
Teacher’s Activity: The teacher defines concrete and aggregates. The teacher then explains the two main types of aggregates (coarse and fine) and their characteristics, using the provided samples for illustration.
Pupils’ Activity: Pupils listen, observe the samples, and ask questions for clarification.
Learning Point: Pupils understand the definition and types of aggregates used in concrete.

Step 3: Demonstration of Aggregates

Time: 7 minutes
Teaching Skill: Demonstration/Visualisation
Teacher’s Activity: The teacher passes around samples of cement, fine aggregate (sand), and coarse aggregate (gravel/crushed stone) for pupils to observe and feel. The teacher highlights the differences in particle size and texture.
Pupils’ Activity: Pupils examine the samples and identify the differences between coarse and fine aggregates.
Learning Point: Pupils can visually and tactilely distinguish between different concrete components.

Step 4: Explanation of Mixing Proportions

Time: 8 minutes
Teaching Skill: Explanation/Analysis
Teacher’s Activity: The teacher explains the concept of mixing proportions in concrete, emphasizing why specific ratios are used. The teacher discusses common ratios like 1:2:4 and 1:3:6, explaining what each number represents (cement:sand:gravel) and their suitable applications. The importance of the water-cement ratio is also discussed.
Pupils’ Activity: Pupils listen, take notes, and ask questions about the different ratios and their uses.
Learning Point: Pupils understand the significance of correct mixing proportions for concrete strength and purpose.

Step 5: Practical Demonstration of Mixing

Time: 7 minutes
Teaching Skill: Practical Demonstration
Teacher’s Activity: Using the instructional materials (cement, aggregates, water, shovel, measuring box), the teacher demonstrates the basic steps of manual concrete mixing, focusing on dry mixing and gradual addition of water to achieve a workable consistency. (This can be a simulated demonstration if actual mixing is not feasible in the classroom).
Pupils’ Activity: Pupils observe the demonstration carefully, noting the sequence of steps and the technique used.
Learning Point: Pupils observe the practical process of concrete mixing.

Step 6: Class Discussion/Q&A

Time: 5 minutes
Teaching Skill: Questioning/Discussion
Teacher’s Activity: The teacher facilitates a short discussion, allowing pupils to ask further questions about aggregates, mixing ratios, or the mixing process. The teacher clarifies any misconceptions.
Pupils’ Activity: Pupils ask questions and contribute to the discussion.
Learning Point: Pupils deepen their understanding through interaction and clarification.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

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

Define concrete.
Mention two types of aggregates used in concrete.
State a common mixing proportion for structural concrete.
List two important steps in manual concrete mixing.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the importance of proper selection of aggregates and accurate mixing proportions for quality concrete. The teacher may give a brief assignment for pupils to research other types of concrete mixes.
Pupils’ Activity: Pupils listen to the summary and note down the assignment.
Learning Point: Pupils recall the main aspects of the lesson.

Lesson Keywords

Concrete – A building material made from cement, aggregates, and water, which hardens over time.
Aggregates – Granular materials like sand and gravel used in concrete.
Coarse Aggregate – Larger aggregate particles such as gravel or crushed stone.
Fine Aggregate – Smaller aggregate particles such as sand.
Mixing Proportion – The specific ratio of cement, sand, and gravel used in concrete.

Differentiation

For pupils who grasp concepts quickly, they can be tasked with identifying local sources of aggregates or researching different types of cement. For pupils requiring more support, additional visual aids, one-on-one explanations, or simplified instructions during the demonstration will be provided. Group activities will encourage peer learning and support.

Note for teachers using this lesson plan

Ensure all materials are prepared before the lesson. If actual concrete mixing is not possible, a detailed step-by-step pictorial chart or video demonstration can be used. Emphasize safety precautions when handling materials like cement. Encourage pupils to relate the lesson to real-world construction they see around them.