Dowel Bar Retrofit
Dowel Bar Retrofit (DBR) is a method of pavement repair that helps to re-establish a pavement’s load transfer integrity by placing steel, epoxy-coated dowels into already existing concrete across joints and cracks. The concrete is cut using a diamond-tipped blade and slots are created. Once the existing concrete has been removed, the dowels are placed in these slots, backfilled with a non-shrink grout, and the concrete is ground to ensure that the pavement remains smooth.
Concrete is very often heavily trafficked and traveled. As a result, roads can become distressed, losing serviceability and support because there are spaces beneath concrete pavement slabs. These spaces are normally located around cracks or joints as a result of surface water that seeps into the pavement. Generally, voids are caused by pumping, subgrade failure, bridge approach failure, and consolidation. Slab stabilization solves the void issue without being destructive and is normally implemented in tandem with other concrete pavement restoration methods like diamond grinding or patching. This method fills the small spaces that are created underneath the concrete slabs and so restores support.
In this method, a cementious grout or polyurethane mixture is pumped into holes that are cored throughout the slab. The grout not only fills in the spaces underneath the slab, but also removes free water and continues to keep water from weakening the support once the slab stabilization has been completed. This process takes three basic steps once the voids have been found: drill holes, pump the slab with grout, and test the slabs post-stabilization.
While helpful, this method of concrete pavement restoration does not increase the design structural integrity, correct depressions, stop faulting, or eliminate erosion. However, it does restore the slab’s support and decreases deflections under heavy traffic. This should only be done where there are cracks and joints where support loss exists. The easiest way to find these spaces is simply visually: transverse joint faulting, shoulder drop off, corner breaks, and lines at or near joints and cracks are all indicators that repair is necessary. Although it is normally easiest to visually search for repair signs, another way to search for voids is by employing deflection testing. It is generally suggested that this testing be done at night.
In concrete pavement, there exist joints by which random, uncontrolled cracking is minimized through a predetermined pattern. They are created by using a diamond blade or are manually input into the concrete. When the pavement is initially created, sealant is installed and once more after the sealant has expired and undergone a certain level of failure. Joint repair, or crack repair, is used to diminish the amount of surface water or other unwanted material that may infiltrate the joint system.
Joint sealants are also used in Concrete Pavement Restoration techniques to help diminish dowel bar corrosion. Resealing involves first removing the old sealant, shaping and cleaning the reservoir, and installing the rod before installing the sealant. In order to remove the sealant, one can saw, plow, cut, or even manually remove the old sealant and saws are often utilized in the shaping of the reservoir. It is important to be thorough when cleaning the reservoir: no traces of old sealant, dirt, or dust should remain and so it is suggested that water washing, sand-blasting, and air blowing the reservoir be done to remove any remaining particles. A double-wheeled, steel roller is used in backer rod installation when inserting the rod to the desired depth. Once the backer rod has been installed, the joint is filled with sealant which can be composed of numerous materials including silicone, preformed compression seals, and hot pour bituminous liquid.