Concrete Susceptible to Corrosion
If moisture is present, then corrosion of steel embedded in the steel reinforced concrete will be an important concern that would require serious attention, since it has extensive financial implications. Damage due to corrosion of rebar may occur in large structures such as residential buildings, bridges, tunnels, due to which these may also become dangerous if appropriate remedial actions are not taken.
The expansion of the corrosion products (iron oxides) of carbon steel reinforcement structures may induce mechanical stress that can cause the formation of cracks and disrupt the concrete structure. If the rebars have been poorly installed and are located too close to the concrete surface in contact with the air, spelling can easily occur: flat fragments of concrete are detached from the concrete mass by the rebar’s corrosion and may fall down.
When reinforcement corrodes, it undergoes a more or less localized dissolution, and it is covered with unstable corrosion products (traditional rust of reddish colour). In a rather porous and wet concrete, these products migrate through the cover and can stain the concrete surface. But, in the more traditional case, for a relatively dry concrete, the corrosion products swell by highly deforming the cover and under such effect can crack the concrete or make spelling.
Tunneling and Mining
GFRP rebar, which is extremely resistant in the fiber direction but easily cut in the orthogonal direction, also offers advantages when sections of the tunnel are cut into creating cross passages between parallel tunnels, emergency evacuation exits and safety niches.
Concrete retaining walls using GFRP as temporary reinforcement, are becoming common worldwide. The benefits of this solution are not only limited to the assembly works; the material’s behavior also enables a simpler demolition / removal with reduced concrete break-out and rebar cutting, enhancing worker safety and accelerating tunnel progress
Building and Historic Preservation
The development of Civil Engineering should be intimately connected to the innovation in structural materials. The GFRP rebar’s can be used for bridge decks & railings, median barriers, roads and slabs on grade, continuously reinforced concrete paving, precast elements, manhole covers, culverts, curbs and parking structures, all sewerage and sanitation members.
Exposure of Concrete to Chemical Environment
Chemical processing industries of all types, as well as wastewater of domestic or industrial origin, constitute major sources of corrosion for steel reinforcement. Typical applications include: wastewater treatment plants; petrochemical plants; pulp and paper mill and liquid gas plants; pipelines and tanks for fossil fuel; cooling towers; chimneys; mining operations of various types, nuclear power plants; and nuclear dump facilities.
Masonry Strengthening
Cracking of masonry walls may occur due to settlement of foundation, during earthquakes, application of lateral loads. There can be several causes for masonry wall cracks, but occurrence of these cracks may lead to complete collapse of wall. Unreinforced masonry walls have good compressive strength, but they are brittle and very weak under the action of lateral loads which causes tension in walls. Whenever tension forces acts on a masonry wall, it tends to crack.
Strengthening of masonry walls is required to prevent failure and collapse during major earthquake or addition of extra load on buildings. Strengthening of masonry walls also may be required during rehabilitation of buildings.
Exposure of concrete to Marine Chlorides
Corrosion of steel reinforcement is a common problem in structures built in or close to seawater. Examples of possible applications: quays; retaining walls; piers; pilings; jetties; caissons; decks; bulkheads; floating structures; canals; roads and buildings; offshore platforms; swimming pools and aquariums.
Exposure of Concrete to High Votages and Electromagnetic Fields
Using steel bars in applications where low electric conductivity or electromagnetic neutrality is needed often results in complex construction layouts, if such use is possible at all. Potential applications are: aluminum/copper smelting plants; manholes for electrical and telephone communication equipment; structures supporting electronic equipment such as transmission towers for telecommunications; airport control towers; magnetic resonance imaging in hospitals; railroad crossing sites; and military structures needing radar invisibility.