Monolithic pour joint

Abstract

There is provided a monolithic pour joint interposed between adjacent concrete slabs disposed on a substrate. The pour joint comprises a plurality of elongate forms interconnected with splices. Each one of the forms has a substantially planar, vertical panel with upper and lower edges and opposing ends respectively defining a form width and a form length. The forms are arranged such that the form lengths are generally aligned end to end. The lower edge of the vertical panel has a base flange extending generally laterally therefrom. A plurality of stakes are disposed in transverse relation to the form width and are secured to a side of the vertical panel at spaced intervals to fixedly maintain the forms in relation to the substrate. The pour joint may include a plurality of dowel holes extending through the vertical panel such that a dowel placement system may be installed in the pour joint.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] (Not Applicable) STATEMENT RE: FEDERALLY SPONSORED RESEARCH / DEVELOPMENT [0002] (Not Applicable) BACKGROUND OF THE INVENTION [0003] The present invention relates generally to concrete forming equipment and, more particularly, to a uniquely configured monolithic pour joint specifically adapted to prevent shear cracking of adjacently disposed concrete slabs. The pour joints are configured to facilitate the placement of dowel rods within adjacent concrete slabs. [0004] During construction of concrete pavement such as for sidewalks, driveways, roads and flooring in buildings, cracks may occur due to uncontrolled shrinkage or contraction of the concrete. Such cracks are the result of a slight decrease in the overall volume of the concrete as water is lost from the concrete mixture during curing. Typical contraction rates for concrete are about one-sixteenth of an inch for every ten feet of length. Thus, large cracks may develop in concrete wh...

AI Technical Summary

Benefits of technology

"The present invention is an improved, monolithic pour joint that prevents shear cracking of adjacent concrete slabs while accommodating slip dowel systems for aiding in the placement of slips dowels within edge portions of adjacent concrete slabs. The pour joint includes at least one elongate form or a plurality of forms arranged in end-to-end alignment with a splice interconnecting the forms and a plurality of elongate stakes secured to a side of the forms. The stakes have a stake body with an upper end and a lower end. The lower end of the stake has a base flange that extends laterally from the vertical panel such that the form defines an L-shaped configuration. The splices are configured to interconnect adjacent ones of the forms at the lower edges and may be secured to the vertical panel with mechanical fasteners such as self-tapping screws. The stakes may also be secured to the lower edge of the vertical panel with stake clips that may be integrally formed with and extendable from the stake body such that the form may be rigidly held at a preset height above the substrate. The pour joint is compatible with dowel placement systems due to the inclusion of dowel holes in the forms and the generally planar configuration of the vertical panel. A layer of resilient joint filler may be included along a side of the vertical panel to prevent the entrapment of stones, debris or other material between the slabs that may otherwise interfere with thermal expansion of the slabs. The joint filler may be fabricated from foam material such as fiber board, closed-cell foam rubber or low density, closed-cell polyethylene foam. An edge cap may also be mounted upon and extend along the upper edge of the form in order to provide protection against water infiltration and particle entrapment within the pour joint."

Problems solved by technology

During construction of concrete pavement such as for sidewalks, driveways, roads and flooring in buildings, cracks may occur due to uncontrolled shrinkage or contraction of the concrete.

Such cracks are the result of a slight decrease in the overall volume of the concrete as water is lost from the concrete mixture during curing.

Thus, large cracks may develop in concrete where the overall length of the pavement is fairly large.

In addition, the cracks may continue to develop months after the concrete is poured due to induced stresses in the concrete.

Although effective in providing longitudinal contraction joints to prevent random cracking, the checkerboard system of concrete pavement construction is both labor intensive and time consuming due to the need to remove the forms and due to the waiting period between the curing of the first batch and the pouring of the second batch of concrete.

Unfortunately, vertical displacement of adjacent slabs may also occur at a joint due to settling or swelling of the substrate below the slab or as a result of vertical loads created by vehicular traffic passing over the slabs.

Such height differential may result in an unwanted step or fault in a concrete sidewalk or roadway or in flooring of a building creating a pedestrian or vehicular hazard.

Furthermore, such a step may allow for the imposition of increased stresses on the corner of the concrete slab at the joint resulting in degradation and spalling of the slab.

Although the key joint presents several advantages regarding its effectiveness in transferring loads between adjacent slabs, key joints also possess certain deficiencies that detract from their overall utility.

Perhaps the most significant of these deficiencies is that the tongue of the key joint may shear off under certain loading conditions.

Furthermore, the face of the key joint may spall or crack above or below the groove under load.

If the vertical load is applied on the tongue side, the failure will occur at the bottom portion of the groove.

Conversely, if the vertical load is applied on the groove side of the joint, the failure will occur near the upper surface of the slab upon which the load is applied.

Shear failure of the tongue and groove may also occur due to opening of the key joint as a result of shrinkage of the concrete slab.

As the key joint opens up over time, the groove side may become unsupported as the tongue moves away.

Vertical loading of this unsupported concrete causes cracking and spalling parallel to the joint.

Such cracking and spalling may occur rapidly if hard-wheeled traffic such as forklifts are moving across the joint.

Another deficiency associated with key joint systems is related to the size, configuration and vertical placement of the tongue and groove within the key joint.

Such spalls occurring from this type of deficiency typically run the entire length of the longitudinal key joint and are difficult to repair.

Furthermore, key joints suffer from an additional deficiency in that slip dowel systems may not be compatible for use with preformed metallic key joint forms due to interference thereof with a flanged base member of the slip dowel system.

Because slip dowels are typically located near the midheight of a contraction joint, the tongue and groove of the metal form may interfere with the installation of the flanged base member of the slip dowel system.

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