Question 1
b) Describe the following curing methods used in concrete production:
(i) ponding;
(ii) sprinkling.
c) Sketch a corner profile for a right angled corner of a building and label four parts.
Observation
Few candidates were able to:
- state the function of cement, sand and crushed stones;
- describe the following curing methods: ponding and sprinkling.
However majority of the candidates failed to answer the questions.
The expected response to question 1 is as given below:
1. (a) function of each of the following constituents of concrete:
Cement - The cement paste covers the surface area of stone and sand particle in the mix and binds them together when the concrete hardens by hydration/acts as a binder.
Sand - To fill the voids or holes in the crushed stones and reduce its harshness.
- It reduces shrinkage; it fills the voids in the mix.
- It reduces shrinkage of cement in the mix.
Crushed stone - It gives strength to the mix.
(b) description of the following curing methods used in concrete production
(i) Ponding - keeping the concrete product in water.
- keeping the concrete to be cured under water.
(ii) Sprinkling: After the concrete is set continuous spraying with water is done to keep it damp.
(c)