The Challenge of Concrete Restoration
Although it was just a line in a movie, there’s a lot of real-world truth to “If you build it, they will come”. Although having people use a structure for its intended purpose has a number of economic benefits, usage also brings with it, wear and tear, and after years of use, the need for restoration may arise.
Whether it’s a parking garage, residential or commercial building, hotel or bridge or a civil infrastructure restoring strength and structural integrity to any concrete structure requires special expertise, especially with respect to selecting and applying the proper materials. In most instances, successfully completing a restoration project presents more challenges than new construction.
The first step in any restoration effort is inspection. Damage and deterioration may not be confined to areas that are visible, and may, in fact, be indicators of more serious issues that are not initially evident. In the case of existing post tensioned structures, there may be little, if any external evidence of deterioration or the evidence may be misleading.
One of the most valuable inspection tools is Ground Penetrating Radar (GPR) scanning. In addition to enabling engineers to locate post tension tendons, GPR is also used to locate rebar, electrical wiring, pipes and voids within concrete slabs. GPR also allows engineers to “see” beneath a concrete slab on grade, to detect subsurface degradation that threatens surface integrity.
A thorough inspection enables restoration engineers to accurately assess the scope of work that needs to be done, thereby assuring that all necessary repairs are efficiently identified and completed. This step is essential to ensuring the safety of the technicians making repairs, and to the people who use a structure while repairs are being made. Actual repair work may span the spectrum, from crack repair to expansion joint replacement to the application of epoxy top coatings to post tension tendon replacement.
Structures that most commonly exhibit relatively rapid deterioration include both precast and post-tensioned parking decks, especially those in areas where de-icing salts, water, and thermal changes are significant factors; condominiums that are exposed to coastal chlorides, and industrial facilities and wastewater treatment plants in which corrosive agents are prevalent.
Although not an outright repair, external post tensioning is a highly effective means of increasing the structural strength of existing structures and potentially eliminating the need for future restoration. External post tensioning is also optimally suited to enable existing structures to accommodate new loading conditions. It is also ideal for adding the support needed for the creation of new openings, or the installation of new elevators.
Concrete slabs are obviously not the only structures that are impacted by corrosion. Columns and beams may also require reinforcement to compensate for deterioration or to enhance structural capacity. Application of fiber reinforced polymers (FRP) is an effective means of restoring or enhancing structural capacity.
Carbon fiber FRP is the preferred material when load capacity is the primary concern; fiberglass FRP is the material of choice when greater elasticity and deformation are required. Additionally, carbon fiber FRP is a highly effective means of compensating for construction “deficiencies” such as the omission of rebar or beams from a structure when originally built.
From inspection services, including GPR scanning, to forensic corrosion and failure analysis, to the design and completion of construction, Tendon Systems offers innovative, cost-effective solutions for virtually any concrete restoration project.