building construction Paper 2 Nov/Dec 2015

Question 1


  • a)  State one function of each of the following constituents of concrete:
  • cement;
  • sand;
  • crushed stone.
  • 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)