MIAMI DOCK, USA.
A composite replacement of a hurricane damaged concrete pile and a wooden dock with BFRP and GFRP precast concrete components elements and gratings was installed in Miami dock.
One of the goals of the project was to eliminate corrosion of the reinforcing steel – in this case Fibre Reinforced Polymers (FRP) composites were used.
The use of seawater in concrete mix allows the production of a more sustainable concrete structure by eliminating the use of freshwater which is a scarce resource, particularly as the global population increases.
Having the ability to produce concrete which can be manufactured using saltwater will remove the stress on fresh water supplies. With this in mind, the University of Miami researched the possibility of manufacturing concrete using non-potable water. The project lead, Dr Antonio Nanni identified the problem of chloride attack of ferrous reinforcement and referred to his past research of FRP he proposed the use of basalt FRP bars from Galen.
The dock is built with a form of sea-water based concrete that University of Miami researchers have developed, The University of Miami calls this product Seacrete.
Dr Antonio Nanni said: “We have completely replaced the steel reinforcement, the issue of corrosion has totally disappeared.”
Where FRP composites were used and why: The project showcased a number of FRP products, among them was basalt FRP from Galen (manufacturing partner to DEVCO). The presence of noncorrosive reinforcement allowed the use of seawater instead of freshwater in the production of the concrete mix.
SPECIFIC DESIGN DETAILS:
The concrete dock was constructed using precast elements of piles, pile caps and slabs. This structure was designed to withstand wind and wave loads of a category five hurricane.
TYPE OF COMPOSITE USED:
The piles and pile caps were reinforced with FRP rebar in place of steel rebar. The slabs were reinforced with basalt fibre reinforced polymer bars and mesh.
PERFORMANCE IN SERVICE:
Basalt FRP reinforcement is unaffected by chlorides and is highly resistant to acids and alkalis meaning that there is no problem using seawater in the concrete mix.
In addition, recycled aggregates can be added to the new concrete mix, previously this had not been an option due to the fact that there could have been chlorides present within the old concrete which would have attacked the structural steel.
Seawater concrete could help limit water usage freshwater usage and increase the longevity of concrete structures. Currently construction codes prohibit see water-based concrete, but the viability of fibre reinforced polymer as a replacement for steel will open up the industry to a more sustainable and cost-effective alternative.
The use of seawater within the production of concrete would enable concrete production on site eliminating the requirement to transport freshwater.
Bridges are built with a projected ‘50 year’ lifespan, but new designs using composite materials have an expected lifespan of over 100 years. A recent study found that corrosion is responsible for three quarters of maintenance costs on bridges; using FRP instead of steel would greatly reduce these maintenance costs.