The construction of various concrete surfaces is typically accomplished by forming a plurality of adjacent concrete slabs separated by expansion joints. When the concrete surfaces are used to support heavy loads, such as those surfaces used as aircraft runways, taxiways, and parking aprons, the heavy loads supported by the concrete surface may cause vertical movement of adjacent slabs.
To control relative movement between adjacent slabs and more evenly distribute loads among the slabs, it is common to provide load bearing dowels which extend between adjacent slabs and across the expansion joints. Various methods of installing the dowels between joints have been used.
According to a first, more or less conventional method, wet concrete is poured into a slab form and allowed to cure. The form is then removed and holes are drilled into the sides of the slab, generally parallel to an upper surface of the slab. After the holes have been drilled, first ends of the dowels are coated with an epoxy and inserted into the drilled holes. The opposite ends of the dowels extend outwardly from the slab into an area adjacent the slab, where additional concrete is poured to cover the outwardly extending ends of the dowels and thereby create an adjacent slab.
U.S. Pat. No. 5,674,028 discloses a second, improved method of installing dowels between adjacent slabs. As seen in this patent, plastic sleeves are inserted into the edges of concrete slabs after the forms are removed, but while the concrete is still relatively plastic. After the concrete hardens, dowels are inserted into the sleeves with an end of each of the dowels projecting outwardly. Thereafter, an adjacent slab is poured, embedding the outwardly projecting ends of the dowels and completing the joint.
Dowel placement sleeves are also described in U.S. Pat. Nos. 5,005,331; 5,216,862, and 5,487,249. In constructions of this type the sleeves are removed after the concrete is hardened. In the '862 patent, for example, it is disclosed that a sleeve may be tapered to facilitate extraction. While this type of sleeve may be relatively easily removed from the void it creates after an initial longitudinal displacement of the sleeve has been effected, a significant amount of force may still be required to break the sleeve free from the cured concrete and obtain that initial displacement.
The prior methods described above have various drawbacks. For example, drilling holes for receiving the dowels after the concrete has cured is a labor-intensive and time consuming process. Furthermore, without adequate controls, the holes drilled into the concrete may not be properly aligned with the top surface of the concrete slab or the edge into which the holes are drilled. Such misalignment may restrict relative movement between the slabs to a point which hinders performance of the expansion joint. While forming voids in the concrete by means of removable sleeves has advantages, it is often difficult, as noted above, to remove the sleeves from the concrete after the concrete slab has cured.
There is thus a need for a device which may be used to form voids in concrete slabs while the concrete is in a plastic state and which overcomes various drawbacks of the prior art, such as those described above.