Concrete Restoration Insights
Concrete deterioration and damage most commonly take the form of surface fractures (cracks). For the most part, some surface cracking is normal and although it may be unsightly, it isn’t necessarily an indication that repair is necessary. However, fracturing of load-bearing concrete is an entirely different matter as it may indicate a structural deficiency that could result in catastrophic failure.
At one end of the fracture spectrum is a residential driveway. Although it’s difficult to find one that doesn’t have at least one crack, many of these cracks remain virtually unchanged for decades. At the other end of the spectrum are any number of structures for which visible fractures are often indications of deeper problems. That’s especially true of structural components that are load bearing, in which case fractures tend to grow rapidly in length and width.
It’s foolish to begin any concrete restoration project before doing an adequate appraisal of the extent of damage. That may mean looking beneath the surface. Unfortunately, lacking Superman’s “x-ray vision”, engineers and technicians can’t see sub-surface conditions, but Ground Penetrating Radar (GPR) can provide the necessary view. In addition to detecting sub-surface damage, GPR is also used to locate areas that should be avoided when drilling or removing sections of concrete- specifically, areas that contain rebar, post tensioning cables or utility lines. GPR is also useful in mapping sub-surface geological conditions which may shed some light on the cause of damage.
Determining the reason that damage occurred is just as important as assessing the extent of the area in need of restoration. Simply removing a damaged section of concrete, and replacing it with new material may not provide a long-term fix. As an example, restoration of a section that failed because sub-standard materials were used requires a different approach than a failure that resulted from slab thickness and/or reinforcement being insufficient to handle the loads imposed. Similarly, failure resulting from changes in sub-surface conditions, or a dramatically changed environment require approaches that specifically address those conditions.
The keys to restoration that will resist the causes of damage to the original structure are the selection of materials and structure design. Virtually all concrete is routinely subjected to weathering action, chemical invasion and abrasion. However, the severity of damaging forces varies with environment. Concrete that’s exposed to seawater requires a different mixture than concrete that serves as a floor or wall in a building. Load-bearing structures require a higher level of reinforcement than non-load bearing slabs.
Any steel-reinforced concrete that’s exposed to water, seawater or high-salt conditions must be of low permeability to minimize intrusion and the resulting rust and corrosion. For the most part, concrete’s high pH creates a protective oxide film on the surface of the embedded steel. Unfortunately, that film is not impervious to the chlorides that can leach into concrete that’s exposed to salt water and deicing chemicals. Consequently, the use of low permeability concrete is essential, as is coverage (concrete over steel) that’s sufficient to adequately protect embedded steel from corrosive liquids.
The advantage of relying on a company like Tendon Systems for concrete restoration projects is the wealth of experience a staff with decades of experience brings to a project. Tendon teams can handle every aspect of a restoration project from evaluation of damage, to determining the most cost-effective solutions, to total project management.