A Self-Learning Manual - Institution of Engineers Mauritius

A Self-Learning Manual
Mastering Different Fields of Civil Engineering Works (VC-Q&A Method) Vincent T. H. CHU
recipe design is based. In case adjustment has to be made to the recipe
design, it is very difficult to determine and assess the modifications
required. Secondly, it poses problem to site engineers to assess the effects
of minor non-compliance if recipe specification is adopted. Finally, the
recipe mix may not be the most economical design which is dependent on
site conditions.
6. Should high-yield steel or mild steel be designed as road
reinforcement? (SR1)
High yield steel is the preferred material for the reinforcement of concrete
carriageway because of the following reasons [55]:
(i) The principal function of steel reinforcement in concrete pavement is to
control cracking. If mild steel is adopted for reinforcement, upon
initiation of crack formation mild steel becomes overstressed and is
prone to yielding. High yield steel offers resistance to crack growth. The
above situation is commonly encountered where there is abnormal
traffic loads on concrete carriageway exceeding the design limit.
(ii) High-yield steel is less prone to deformation and bending during routine
handling operation.
(iii) In the current market, steel mesh reinforcement is normally of high-yield
steel type and the use of mild steel as road reinforcement requires the
placing of special orders to the suppliers.
7. In which direction should the main weight of reinforcement be
placed in concrete pavement? (SR2)
The reinforcement of concrete pavement is usually in the form of long
mesh type. A road usually has length is generally much longer than its
width and therefore cracking in the transverse direction has to be catered
for in design. Reinforcement is required in the longitudinal direction to limit
transverse cracking while transverse steel acts to provide rigidity to support
the mesh fabrics. For long mesh in concrete slab, the main weight of
reinforcement should be placed in the critical direction (i.e. longitudinal
direction) to control cracking. However, if the concrete road is quite wide,
certain reinforcement has to be placed in the transverse direction in this
case to control longitudinal cracking [55].
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