For concrete carriageway, it is normally classified into two types: reinforced and

unreinforced concrete pavement. The reinforcement in reinforced carriageway (in the form

of mesh) is used for controlling cracking. Then one may query how unreinforced pavement

can control cracking without the use of mesh reinforcement. To answer this question, one

should pay attention to the features of unreinforced concrete pavement. In accordance with

Highways Standard Drawing No. H1109, an approximately 3mm wide groove with a depth

of about one-third to one-fourth of slab thickness is designed with a regular spacing

(normally 5m). The grooves are designed to be too narrow for stones to fall into when the

cracks are open due to concrete contraction. The sectional area in which the groove is

located is a plane of weakness and thus this groove acts a potential crack-inducing device

in which any potential cracks due to shrinkage and thermal contraction may form.

Consequently, the cracks are formed at the base of the groove and thus it would not cause

any unpleasant visual appearance on the exposed surface of unreinforced concrete

pavement.

Fig. 6.1 Crack formed in unreinforced

concrete pavement.

2. Why are concrete profile barriers designed with curved surface profiles?

Safety fencings are designed to contain vehicles in the carriageway in which they are

traveling and prevent them from rebounding into the road and causing hazards. For normal

fencing design, when vehicles crash into safety fencings, it will give way so as to absorb as

much energy as possible, thus reducing the impact forces on the vehicles. Moreover, it

serves to realign the vehicles along the carriageway when vehicles hit on them. However,

for concrete profile barriers they are not designed to absorb energy during vehicle crashing,

but to hold the vehicles hitting on them. In this connection, concrete profile barriers are

designed with curved profiles so that vehicles can mount and go up partly on them, and yet

they will not cause overturning of vehicles. Reference is made to Arthur Wignall, Peter S.

Kendrick and Roy Ancil.

For shallow-

Dear Dr. Abbas,,your answer is highly appreciated