VII. A) Which materials do you think can be used for different building components?

Give your reason.

b) In pairs, use the table below together with the table in Exercise VI, to make conversations like the following:

CLIENT: What do you think is the best material to use for the cladding?

ARCHITECT: Well, aluminium isn't really suitable. It's strong enough but it's too expensive. I

think we should use mild steel. It's not only strong enough but it's also cheaper.

cladding	aluminium mild steel	A tensile strength of mot less than 90 N/mm²
beam	pine oak	A tensile strength of not less than 35 N/mm²
roof covering	zinc cooper	Weight should not exceed 8000 kg/m³
Fire door	mild steel cooper	Melting point should be in excess of 1000 ºC

VIII. A) Read the passage about concrete:

Concrete is made from cement, coarse aggregate (stones), fine aggregate (sand or crushed stone) and water. Coarse aggregate ranging from 5 mm to 40 mm may be used for normal work. The maximum size of the aggregate should not be greater than one quarter of the minimum thickness of the finished concrete. The normal maximum sizes are 20 mm and 40 mm (20 mm being more common). The maximum size of aggregate which should be used in small concrete sections, or where reinforcement is close together, is 10 mm.

Reinforced concrete section

In concrete with widely spaced reinforcement, such as solid slabs, the size of the coarse aggregate should not be greater than the minimum cover to the reinforcement otherwise spalling will occur, i.e. the breaking off of pieces of concrete below the reinforcement. For heavily reinforced sections, e.g. the ribs of main beams, the maximum size of the coarse aggregate should be either:

(i) 5 mm less than the minimum horizontal distance between the reinforcing rods, or,

(ii) 5 mm less than the minimum cover to the reinforcement, whichever is the smaller.

b) Now mark the sentences below T (true), F (false) or N (no information in the text). Correct the false statements.

1) Concrete is made from three different materials.

2) Coarse aggregate ranges in size from 20 mm to 40 mm.

3) When the minimum thickness of the finished concrete is 100 mm, the maximum size of aggregate should not be greater than 25 mm.

1) When the reinforcing rods are close together, the maximum size of aggregate used should be 10mm.

2) Cover is the thickness of concrete between the reinforcing rods.

3) The reinforcing rods are placed near the bottom of the rib of a concrete beam.

4) Spalling can occur in a solid concrete slab when the cover to the reinforcement is greater than the maximum size of the coarse aggregate.

5) When the minimum horizontal distance between reinforcing rods is 15 mm, the maximum size of aggregate should be less than 12 mm.