Concrete structures, such as tunnels, pavements, bridges, foundations, and the like, are often prone to the development of cracks. Concrete contracts and expands with changes in moisture and temperature, and can deflect based on the load applied to the structure and the support conditions for the structure. While cracks can more easily develop in concrete structures as a result of improper design and construction practices, all concrete structures will, regardless of construction techniques, have some tendency to develop cracks. That tendency may increase as a result of particular mechanical loads on the concrete structure, settlement, shrinkage in both fresh and hardened concrete structures, temperature changes, corrosion, and the like.
Of course, the development of significant cracks in concrete structures can adversely affect the performance of such structures. Thus, efforts have been made to provide for the control and repair of cracks in concrete structures. For instance, attempts have been made to control crack development by optimizing the composition of the concrete structure through material selection and proportioning, optimizing construction practices for the particular structure and its use conditions, and the like. Further, attempts have been made to provide for the repair of cracks in concrete structures, such as by filling the crack with sealers, such as epoxy, methacrylate, urethane, mastics, thermoplastics, elastomers, vinyl ester resin, amine resin, polyester resin, and the like, all with and/or without prior machining and shaping of the crack, along with structural reinforcement of the structure surrounding the area of the crack (e.g., placing a grid of reinforcing steel over the cracked area).
For example, one prior technique for attempting to control water leakage through cracked concrete elements has comprised dry packing oakum that was impregnated with a binder (e.g., pine-tar, asphalt and coal tar residues, water reactive mastics, caulks, sealants and liquid urethanes) into the crack, at times with other hydrophilic components. Upon contact with water, the impregnated oakum would expand to close the crack. Likewise, Cured-In-Place polymeric seals have been used (e.g., rigid epoxy mastics and flexible sealants) in routed-out cracks for surface seals, with back-rods and/or bond-breaking tapes and composites placed in the base of the routed slots. Similarly, cementitious grout plugs have been used to plug routed-out slots, and flexible and rigid sheet composites have been placed over the leaking crack or joint and affixed to the concrete surface. Each of these prior attempts, however, have had their respective shortcomings and have not been entirely suitable for the long term waterproof sealing of cracks that are prone to opening and closing over time.
A particular challenge exists with regard to the repair of concrete structures exposed to hydrostatic water pressure, such as many tunnels. Water intrusion into cracks in concrete can accelerate corrosion of reinforcing steel and lead to deterioration of the concrete itself. Control and repair of such cracks, while critical to maintaining the integrity of the structure, can be difficult. Typically, in attempting to seal a leaking crack in a concrete structure, a chemical or cementitious grout is injected into the crack.
However, injecting cracks with such fill materials often prove insufficient, as the seal provided by such material tends to fail as the crack opens and closes over time. For example, U.S. Pat. No. 6,309,493 issued Oct. 30, 2001 describes a method for filling cracks in a concrete structure with foamable polyurethane prepolymer, and provides an injection port that can be utilized for delivering a foaming solution to a crack in the concrete structure. While potentially suitable for temporarily sealing small cracks in concrete, such application would not be suitable for the permanent, water-tight sealing of significant cracks in concrete structures, as the continuous expansion and contraction of the concrete would quickly break the seal formed by such material.
Similarly, Japanese Patent Publication No. 62-236884 published Oct. 16, 1987 describes a method for repairing a crack in concrete, which process includes creating a chamber at a leakage point, inserting an impregnating pipe into the chamber, and applying a rapid bonding agent around the impregnating pipe to seal the chamber. Grout is then applied to the chamber through the impregnating pipe. The grout, in the form of polyurethane, reacts with moisture in the chamber and expands, thus sealing (at least temporarily) the crack in the concrete. Once again, while potentially suitable for temporarily sealing small cracks in concrete, such application would not be suitable for the permanent, water-tight sealing of significant cracks in concrete structures, as the continuous expansion and contraction of the concrete would quickly break the seal formed by such material.
It is important that repairs of concrete cracks provide a permanent, water-tight seal that resists the ingress of water even as the crack continues to open and close. Joint systems have previously been provided for sealing finished joints in various structures, such as bridges, tunnels, parking decks, stadiums, buildings, reservoirs, and waste water treatment facilities by using expansion joints. One such example of an expansion joint is shown in U.S. Pat. No. 4,884,381 issued Dec. 5, 1989, which provides a joinder system for providing a seal between a pair of opposed walls. The system has a sealing element with a longitudinal cavity and a plurality of ribs, and is placed between two structural elements, such as a pair of opposed walls of a roadbed or building. Adhesive material is applied between the sealing element and the opposed walls. After the sealing element is placed at a desired location between the two walls, a filler material is injected into the longitudinal cavity under pressure causing the sealing element to expand and the ribs to press the adhesive material into the walls. While such systems may be useful in providing a sealing joint between planar wall surfaces and similarly configured, finished joint faces, they are typically not suitable for use in sealing irregularly shaped cracks that may randomly form in the concrete structure.
Unfortunately, as the foregoing attempted solutions tend to fail once the crack opens, causing the injected material to break down and/or separate from the edges of the crack and thus allowing water intrusion to continue, they have not proven to be permanent solutions. Thus, there remains a need in the art for an effective means of permanently sealing leaking cracks in concrete that are subject to opening and closing over time. It would thus be advantageous to provide a method and system suitable for permanently sealing irregularly shaped cracks in concrete structures in a water-tight manner that maintain a seal even through the ongoing opening and closing of the crack.
USPTO Backgrounds
USPTO Backgrounds