Carpentry for Vocational Schools - A Teachers Handbook
 3. CONCRETE
 (introduction...) 3.1. Composition of concrete 3.2. Proportions for mixing concrete 3.3. Reinforcing concrete 3.4. Finishing concrete

### (introduction...)

TOPIC: 3. CONCRETE

INTRODUCTION: This topic teaches students what concrete is made of; the right proportions of sand, gravel cement and water; how concrete is reinforced and how to finish a slab.

Concrete work is an important part of building a house, but this topic is quite broad and it might be difficult to teach the whole topic. Select those chapters where a real need exists according to the aim of the school.

OBJECTIVES:

3.1. Students must be able to name the raw materials in concrete and describe their characteristics.

3.2. Students should know the meaning of the "ratio" used in mixing concrete and the amount of each material needed to make one cubic metre of concrete. Students also should know the correct ratio for different purposes like foundations, walls or concrete blocks.

3.3. Students must know why concrete has to be reinforced, the, different reinforcement bars and meshes, its applications and the correct way reinforcement bars or mesh are laid.

3.4. Students should be able to describe the correct procedure for making a smooth finish of a concrete surface and the tools needed for this job.

METHODS:

3.1. First the objective is introduced in the classroom. We prepare samples of cement, sand and gravel to show the materials concrete consists of.

3.2. After explaining this chapter in the classroom, the samples of cement, sand and gravel are mixed in the right proportions with water. A small wooden form is prepared where the concrete is poured, consolidated and smoothed.

3.3. Prepare samples of different reinforcement bars and mesh and display them in the classroom where we explain their characteristics and uses. Demonstrate how reinforcement bars and mesh are jointed when necessary.

3.4. Again, prepare a small wooden form and after the explanation in the classroom, mix some concrete and pour into the wooden form where some reinforcement bars have been placed. Strike off the excess concrete and smooth the surface as described earlier in this chapter.

NOTE: The size of the wooden forms should not exceed 500 mm x 500 mm and 60 mm in height. When both concrete samples have been moved to dry for at least one week, take out the wooden forms and try to break both by supporting the concrete only on two outside edges and placing a heavy load in the middle. Students will see, that concrete without reinforcement will break easier.

At the end of this topic prepare a worksheet with questions for the students to reinforce this topic.