Steel dowels, when aligned carefully and debonded from the concrete, help to carry loads across joints in concrete slabs even after the joints have opened too much to prevent load transfer by aggregate interlock. However, traditional round dowels may cause slab cracking by restraining movement along doweled longitudinal joints when workers place large floor slabs in long, alternating strips, with infill strips placed later. When the infill concrete tries to shrink, the dowels prevent slab movement parallel to the longitudinal joint, causing internal stresses.
How can engineers economically design for load transfer at joints without restraining movement? Many are solving the problem by using rectangular- or diamond-shaped plate dowels or square dowels fitted with compressible sleeves. Rectangular- and diamond-shaped plate dowels are more cost-effective than round dowels because they use material more efficiently. Workers insert the plate dowels into leave-in-place ABS plastic pocket formers with a tight vertical fit that transfers loads across the joint but still allows for slab shrinkage movement. Square dowels can be fitted with a clip-on device that puts the sides of the dowel in contact with a compressible material. This permits movement along longitudinal joints, reducing restraint cracking.
