Dowel and tie bars

The dowel bars are recommended to be plain round steel bars of grade 250 N and 450 mm long, placed at 300 mm centres. More than half of the length of the dowel bar should be coated with a debonding agent to ensure effective debonding from the concrete on that side of the joint. The dowel diameters vary from 24 to 36 mm, depending on the slab thickness. 

Tie bars are recommended to be 12 mm in diameter, grade 500 N deformed steel bars, 1 m long and placed centrally in the joint. The spacing is determined accordingly depending on the thickness of the concrete slab, the interlayer friction and the distance to the nearest free edge of pavement. 

More details about reinforcement design, joint spacing and joint construction can be found in Austroads (2012). 

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Settlement or faulting is caused by compaction/consolidation or shrinkage of the layers underlying the slab, movements in the underlying ground or lack of effective load transfer between slabs at joints (effectiveness of dowels and tie bars). 

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