Page 9 - zana-training e book

2.3 Water

The water used for brewing the concrete must be free of materials that leave an
impression such as silt, clay, organic acids and other organic substances such as
salt and alkali.

Usually the water used for brewing the concrete is drinkable water or obtained
from an approved source.

3.0 Advantage and Disadvantage of concrete in construction industry.

Advantage of concrete:
i. Economical.
ii. High compressive strength.
iii. Resistant to corrosion and fire.
iv. Durable.
v. Easy to form any desired shape.
vi. Reinforced with steel gives unlimited application.

Disadvantage of concrete:

i. Low tensile strength.
ii. Cracks easily.
iii. Fresh concrete shrink when drying, hardened concrete expand when wet,
require provision at joints.
iv. Expand & contacts with temperature changes.
v. Disintegrate by alkali & sulphate attack.
vi. Permeable to moisture & contain soluble salts which cause efflorescence.

4.0 Type of cement

Cements can be classified into nine types:
i. Ordinary Portland Cement (OPC)
ii. Rapid Hardening Cement (RHC)
iii. Sulphate-Resisting Cement (SRC)
iv. Low Heat Cement (LHC)
v. High Alumina Cement