Page 3 - zana-training e book

CHAPTER 1

1.0 CONCRETE MATERIALS AND MIXTURE

Concrete is a construction material obtained by mixing a binder (such as cement,
lime, mud etc.), aggregate (sand and gravel or crushed aggregate), and water in
certain proportions.

2.0 Materials in concrete mixture

2.1 What is Cement

Cement can be described as a material with adhesive and
cohesive properties which make it capable of bonding
mineral fragments/aggregates into a compact mass.

Function:

1. To bind the sand and coarse aggregate together.
2. To fill the voids in between sand and coarse aggregate particles to form a
compact mass.

Manufacture of cement

i. Mixture of argillaceous (clay or shale) and calcareous materials (chalk or
limestone) or, in other words; limestone, sand, clay, and iron ore are
blended, ground, and heated to 1400°C – 1550°C in a rotating kiln such that
chemical combination occurs, and produced material which is called
‘clinker’.
ii. 5% gypsum is added to the resulting clinker to prevent ‘flash’ setting.
iii. Important minor components include the alkali, sodium and potassium
(can affect the setting time, strength development, and the durability of
concrete).