Marine and coastal infrastructure—including piers, seawalls, docks, and bridges—is constantly exposed to some of the most aggressive environmental conditions: saltwater, moisture, chlorides, and varying temperatures. One of the most persistent and costly problems in these environments is steel rebar corrosion in reinforced concrete structures.
Glass Fiber Reinforced Polymer (GFRP) rebar, also referred to as vergalhões compostos or non-metallic reinforcement, offers a highly effective and scientifically validated alternative to traditional steel rebar in marine applications. This article explores how GFRP addresses corrosion challenges in marine construction, with data, case studies, and lifecycle comparisons.
The Corrosion Challenge in Marine Construction
Steel rebar corrodes in chloride-rich environments, which leads to:
- Expansion and cracking of concrete
- Reduced load-bearing capacity
- Shortened service life
- Expensive maintenance and repair cycles
According to a 2023 report by the American Society of Civil Engineers (ASCE), over $20 billion is spent annually in the U.S. on repairing corrosion-damaged marine infrastructure.
In salt-laden air and submerged conditions, chloride ions penetrate concrete and reach the steel, initiating rust formation. As rust expands, it causes concrete spalling, often requiring full structural replacement within 20–30 years.
GFRP: A Corrosion-Free Alternative
GFRP rebar is made from continuous fiberglass filaments embedded in a polymer resin matrix, typically vinyl ester or epoxy. It is 100% non-metallic, meaning:
- No electrochemical corrosion
- Unaffected by chlorides or salt spray
- No need for protective coatings
| Propriedade | Barra de aço | GFRP Rebar |
| Resistência à corrosão | Poor | Excellent (Non-corrosive) |
| Service Life (Marine) | 20–30 years | 80–100+ years |
| Maintenance Needs | Alto | Minimal |
| Life Cycle Cost (LCC) | Alto | 30–40% Lower |
Real-World Applications and Case Studies
Case 1: Seawall Restoration – Naples, Florida (USA)
- Original seawall built in 1985 with steel rebar.
- Severe corrosion detected after 27 years.
- Reconstructed in 2014 with GFRP rebar.
- Zero signs of corrosion or degradation after 10+ years.
Case 2: Wharf Structures – Port of Yokohama (Japan)
- GFRP used in dock slabs and retaining walls.
- Designed for 100+ year service life in tidal and splash zones.
Case 3: Fish Farming Facilities – Norway
- Concrete tanks and channels reinforced with composite rebar to eliminate contamination and extend lifespan.
These projects demonstrate the technical reliability and long-term savings of GFRP in real-world marine environments.
Performance Under Marine Exposure
GFRP has undergone extensive durability testing under simulated marine conditions:
- ASTM D7705: No significant strength loss after 12 months submersion in seawater at 60°C.
- ACI 440.1R: Endorses GFRP use in marine structures.
- CSA S807: Recognizes GFRP as a viable alternative to steel in aggressive environments.
GFRP is also immune to:
- Galvanic corrosion
- Carbonation
- Microbiologically Influenced Corrosion (MIC)
Design Benefits Beyond Corrosion Resistance
Besides immunity to corrosion, GFRP offers:
- Light weight (75% lighter than steel) → Easier transport and faster installation
- High tensile strength (1000+ MPa) → Comparable or better than steel
- Non-conductivity → No interference with instrumentation or marine sensors
These characteristics make GFRP especially suitable for offshore platforms, coastal bridges, and harbor facilities.
Life Cycle Cost (LCC) Analysis
Though initial cost per kg of GFRP is higher (~$1.6 vs $0.8 for steel), overall cost is significantly reduced due to:
- No corrosion-related repairs
- Longer service intervals
- Minimal maintenance
Example: A marina in New Zealand reported a 35% total cost reduction over 50 years using GFRP in pier construction versus steel.
| Cost Element | Steel Structure | GFRP Structure |
| Initial Material | Lower | Higher |
| Repair Frequency | Every 10–15 years | None expected |
| LCC (50-year span) | $1.00M | ~$650K |
Regulatory Support and Adoption
GFRP is approved by multiple international codes:
- ACI 440.1R (USA)
- CSA S807 (Canada)
- EN 1992-3 (EU draft)
- FDOT and Caltrans Guidelines
These recognitions ensure GFRP adoption in public infrastructure, ports, and defense projects.
Conclusion: The Future of Marine Reinforcement
In environments where chloride attack, moisture, and salt are inevitable, steel rebar becomes a liability. GFRP rebar is the long-term, technically superior solution, offering corrosion resistance, economic benefits, and regulatory compliance.
With rising demands for durable and sustainable infrastructure, composite rebar is leading the transformation of marine construction. If you’re planning to build or retrofit coastal infrastructure, Composite-Tech provides cutting-edge GFRP rebar production equipment—engineered for performance, efficiency, and international standards.
