Bridge Waterproofing
The viaduct over the Antuã River, located along the A1 Motorway between Albergaria and Estarreja, is a key bridge structure within Portugal’s main north–south transport corridor. The infrastructure consists of two independent decks—one for each direction of traffic—with a total length of 235 metres, a width of 15 metres per deck, and an overall surface area of 7,050 m².
As part of a major rehabilitation programme, the concrete bridge deck was fully replaced, creating an ideal opportunity to upgrade the waterproofing system. To ensure long-term durability, structural protection, and compatibility with modern asphalt paving techniques, the project team selected S&P Glasphalt® GV, an advanced asphalt reinforcement and waterproofing solution.
Project Description
Situation
Traditionally, bridge decks in Portugal were waterproofed using asphalt sheets. Although once common, this method has increasingly become unsuitable for modern bridge management due to several limitations:
1. Slow and Complex Installation
Asphalt sheets require extensive preparation and careful placement. Their installation is labour‑intensive and significantly slows down construction timelines—an important drawback on busy highway structures.
2. Insufficient Flexibility
The sheets’ rigidity prevents them from adapting to small surface irregularities in the concrete deck. This leads to imperfect bonding and increased risk of water infiltration over time.
3. Poor Compatibility with Construction Traffic
Trucks and bituminous mix spreaders frequently damaged the sheets during paving operations, compromising the integrity of the waterproofing system even before the asphalt layers were placed.
The Risk of Inadequate Waterproofing
Without a reliable membrane, water infiltration can cause:
- Corrosion of the concrete structure
- Rusting of the steel reinforcement
- Accelerated deterioration and costly repairs
Given the complete replacement of the concrete deck and the limitations of traditional sheet systems, the project required a fast, robust, and highly adaptable waterproofing and reinforcement solution.
Solution
S&P Glasphalt® GV Waterproofing System
To meet the project’s performance and durability requirements, the contractor implemented a modern waterproofing system combining:
1. Anionic Bituminous Emulsion (Type EA UNE 104231)
- Produced with chemically modified bitumen containing elastomers (Elaster)
- High adhesion to the concrete substrate
- Forms a continuous, elastic, watertight membrane
- Applied at 1,800 g/m² minimum
2. S&P Glasphalt® GV Reinforcement Grid
Because the bridge deck was completely renewed, S&P Glasphalt® GV—a glass-fibre-based reinforcement with integrated geotextile—was selected to improve waterproofing reliability and enhance asphalt performance.
This system provides:
- A flexible membrane that adapts to minor surface variations
- Fast and straightforward installation
- Full compatibility with bituminous mix applications
- Long-term structural protection against water ingress
Execution: Sequence of Works
The works followed a structured and controlled sequence to guarantee the integrity of the waterproofing system:
- Milling of existing bituminous layers
Removal of old asphalt to expose the new concrete deck. - Thorough cleaning of the deck
Ensuring optimal adhesion between concrete, emulsion, and reinforcement. - Application of waterproofing emulsion
Uniform distribution at 1,800 g/m². - Laying of S&P Glasphalt® GV
Installed manually before the emulsion broke to guarantee bonding. - Application of new asphalt layers
Once the emulsion achieved proper breaking and curing.
Application Precautions
- Installation was carried out in 2.0‑metre strips.
- New strips were started before the previous ones fully cured to prevent walking over fresh emulsion.
- Forklifts were avoided due to the risk of slipping on the freshly applied emulsion.
- A roller was not used for the same reason.
Outcome
The combination of S&P Glasphalt® GV with a high‑performance elastomer‑modified emulsion delivered a durable, flexible, and efficient waterproofing system. The solution ensured structural protection, simplified construction logistics, and improved long-term resistance of the asphalt layers—helping secure the viaduct’s performance for decades to come.
Material
S&P Glasphalt® GV