Bridges Supported with Reinforced Concrete Foundation and Steel Superstructure can Extend its Service Life and Reduces Maintenance Costs when Protected Against Moisture Laden with Salt ions and Acidic Corrosive Gases:
Bridges built with reinforced concrete and steel superstructure are some of the most important infrastructures for economic and civil activities. When properly maintained and serviced, they can be used for hundreds of years.
Modern bridges can now be built over miles of ocean and across some of the highest mountain to provide the convenience of travel for citizen and business activities. Mechanical support redundancy and safety engineering are dramatically improved in recent years. The basics for long-term safety and durability are still the same. That is, maintenance and repairs before major weakening and damages.
The patent-pending AIT FLUOROSEAL® concrete and corrosion protection coatings and methods that block off all of the deleterious elements from penetrating inside reinforced concrete support and the surface and interface between coating and steel infrastructure changes the paradigm of protecting bridge from weakening and corrosion.
Protecting the bridges as infrastructures is normally focusing on the protection of the steel superstructure that are well-known to longer term corrosion even when covered with extensive mechanical protection coatings such as epoxy and polyurethane. The coatings on the bridges are that showed signs of degradation and corrosion typically stripped periodically and recoated for safety and durability.
Steel supporting structures and reinforced concrete foundations require periodic maintenance. Bridges that pass over seas and rivers vehicle traffic are particularly vulnerable to the exhaust corrosive gases and ionic salts in salt-fog and salt-spray. FLUOROSEAL® concrete and corrosion protection coatings put immediate stop to further degradation and weakening.
Repairing and repainting protective coating fractures and delamination are some of the more obvious and repairs that are done for well-maintained bridges.
Steel superstructures rusting and delamination are primarily caused by UV damaging of the epoxy and polyurethan coatings. These coating are with fundamental polymer molecular structure that are more susceptible to penetration of moisture and moisture laden with salt ions and acidic gases. These deleterious elements along the interfaces of steel and coating induces rusting and delamination. The following is an illustration of this vulnerability while also showing the effectiveness of FLUOROSEAL corrosion protection coating CPC-7150 over-coating directly on the epoxy coating to prevent and stop these damaging elements from penetrating and protecting the epoxy coating from UV damaging.
Any break or breach into the well protected steel infrastructure causes penetration by salt-spray or ions laden moisture such as salt-fog to cause corrosion. In this above experiment, a fully FBE coated steel bar is cut on both sides. One side is left exposed to simulate loss of protective coating (can be mechanical accident or stress concentration corner) while the other side is coated with FLUOROSEAL® CPC-7150. When the steel pieces in submerged in slight warm (60°C) salt-water to accelerate the penetration and corrosion. The side NOT PROTECTED with the top-coating of FLUOROSEAL® quickly corroded with migrate inward towards the securely coated areas while the exposed steel protected showed no sign of corrosion including the top-coated epoxy surface.
Even though most bridge corrosion and failures occurred at the steel superstructure, reinforced Concrete foundation supporting the bridge super-structure are often not protected or maintained. FLUOROSEAL® CRC-V-7130 coating gives peace of mind and maintenance free protection to these most important anchoring support structure besides the critical steel superstructure.
Concrete structure and foundation repairs are much more elaborate and often requires substantial rebuilding that cost both money and long duration of out-of-services.
The reinforced concrete supports and decks showed obvious signs of alkali and carbonation weakening. Major cracks are also developing that forces the Seattle bridge on the right to close for a long rehabilitation. Stopping the concrete weakening by blocking off the corrosive and chemical reaction weakening with field application FLUOROSEAL before needing major rebuilding is one of the most critical safeties upgrading and cost-effective maintenance.
To be effective in protecting the reinforced concrete from concrete carbonation and weathering weakening and rebar corrosion weakening, the coating must at least meet the following requirements:
- Field applicable in coating onto the large areas of exposed reinforced concrete structures. That is by roller or brush or spray coating method and “cure” at ambient.
- The coating must be itself resistant to UV exposure for more than 50 years: so that the protection coating does not need constant maintenance. Preferably, the coating should also block UV from reaching underneath the coating to prevent UV damages to the structure or other coating on the structure.
- The coating must have ability to block moisture penetration inside the concrete. Lesser moisture penetration will prevent the water pockets to be accumulated inside the concrete pores and concrete-rebar interface. Lesser moisture also reduces the possibility of Cl-, Na+ and other salt ions being carried along to cause alkalization and rebar corrosions.
- The coating should have the ability to block corrosive gases such as CO2, H2S from carried by the moisture or penetration and react with the retained waters inside the concrete pores and rebar-concrete interfaces. FLUOROSEAL® concrete protection coating CRC-V-7150 with PVDF molecular structures are proven to provide the highest barrier capabilities of field applicable coating.