STEEL REINFORCEMENT FOR CRACK WIDTH CONTROL

For over 65 years, steel reinforcement has been used in the construction of concrete
pavements in an effort to control the opening of concrete cracks. To achieve
approximately uniform opening at all cracks, sufficient steel reinforcement must be used
to prevent the steel yielding at cracks, as the pavement’s concrete shrinks. If the steel
yields, the joint will open excessively. Calculation of the reinforcement required to
prevent the steel yielding, involves consideration of the following variables:
• Length of pavement with continuous reinforcement
• Subgrade friction
• Magnitude of thermal shrinkage
• Magnitude of drying shrinkage
• Required crack width
• Required crack spacing
• Use of stress concentrators (e.g. sawcuts)
• Pavement thickness
• Concrete’s tensile strength
• Diameter of steel reinforcement
• Yield stress of steel reinforcement
In the case of continuously reinforced concrete pavements constructed on a concrete
sub-base, steel reinforcement equal to between 0.6% and 0.7% of the pavement’s cross
sectional area is typically specified. This quantity of reinforcement is capable of
producing maximum crack widths of between 0.5 and 0.6mm, at an average spacing of
1.2 metre centres. Such continuously reinforced concrete pavements can extend for
kilometres without a termination point.
For buildings, minimum reinforcement of 0.14% is recommended (i.e. SL82 mesh in a
150mm thick pavement) for concrete pour lengths of up to 25 metres (Cement Concrete
& Aggregates Australia, 2009). With the increasing use of laser screeds, it is not
uncommon to have single concrete pours over 50 metres long, in which case
significantly more than minimum reinforcement will be required.