A New Perspective in Aging Bridge Repair: 'Water Environment Conservation' - WHiTE Co., Ltd. Proposes Containment-Type Repair Method

Applicable over existing fluoropolymer coatings with SSPC-SP 3 surface preparation. Proposing a 'containment-type repair' aimed at reducing stripping costs, industrial waste, and the risk of paint chips falling into rivers and marine areas.

WHiTE Co., Ltd. (Headquarters: Kagoshima City, Kagoshima Prefecture) is strengthening its proposals for public infrastructure using its 'WH Series' of water-based repair materials to address the aging of structures like bridges, tunnels, port facilities, public buildings, and factory equipment.

As social infrastructure such as bridges and tunnels ages across Japan, municipalities and infrastructure managers are required to advance systematic repairs and extend service life to ensure safety, all within limited budgets and personnel.

Meanwhile, bridge repair presents not only the challenge of ensuring the safety of roads and structures but also the important task of considering the rivers and seas flowing beneath the bridge, surrounding fishery resources, and the local environment.

The concern that existing coatings on bridges may peel off due to age and fall into rivers and seas is a significant issue for both fishery stakeholders and local residents.

WHiTE Co., Ltd. has received feedback from fishing cooperative officials concerned about the degradation and peeling of existing solvent-based coatings on bridges, and the falling of old paint chips during recoating work. Against this backdrop, interest is growing in the WH Series, which protects structures with water-based materials while utilizing the existing coating, from the perspective of water environment conservation.

## From 'Strip and Dispose' to 'Utilize and Contain' Repair

The conventional method for recoating bridges and steel structures has been to remove the deteriorated existing coating, prepare the substrate, and then apply a new paint system.

However, repairs involving full stripping are not only costly and time-consuming but also place a heavy burden on the site and surrounding environment, dealing with issues like scattering and falling paint chips, dust, industrial waste, construction odors, and handling of organic solvents.

The WH Series allows for a 'containment-type' repair proposal that utilizes the sound existing film rather than removing it entirely, after assessing its adhesion and deterioration status.

Even over existing solvent-based coatings like fluoropolymers, a protective layer of water-based repair material can be formed by treating defective areas, rust, and fragile parts with surface preparation based on SSPC-SP 3 (power tool cleaning).

This provides an alternative for maintaining and extending the life of bridges and steel structures while suppressing stripping work, industrial waste disposal, traffic restrictions, construction period, and environmental impact during construction, compared to repair methods that assume full stripping.

## Reducing Stripping Costs Contributes to Both Municipal Finances and Environmental Load

In public infrastructure repair work, the total construction cost is a major burden, encompassing not just material costs but also paint stripping, surface preparation, industrial waste disposal, scaffolding, traffic restrictions, curing, and the construction period.

Especially in steel bridge recoating, processes like SSPC-SP 5/NACE No. 1 (white metal blast cleaning) or SSPC-SP 10/NACE No. 2 (near-white blast cleaning) may be required, and these surface preparation costs can significantly drive up the total project cost.

A reference comparison created by WHiTE Co., Ltd. based on public works examples and actual estimates shows a potential reduction of about 24.8% to 47.3% in the overall process when conventional specifications are replaced with a water-based repair specification.

Actual estimate cases also confirm that the main factors in the cost difference are not the paint itself but the surface preparation process, with coating removal, surface treatment, and cleaning costs being the primary cost drivers.

The WH Series, by performing maintenance repair based on SSPC-SP 3 after assessing the state of the existing coating, has the potential to suppress stripping costs and waste disposal fees.

This goes beyond simply lowering construction costs. Suppressing stripping work also leads to the inhibition of paint chip and dust generation, reduction of industrial waste, mitigation of falling risks into water bodies, and improved safety at the construction site.

In other words, the containment-type repair by the WH Series is a method that aims to simultaneously reduce the financial burden on municipalities and show consideration for the surrounding environment, including rivers and seas.

## Interest from Fishery Stakeholders: Turning Bridge Repair into 'Work that Protects Local Waters'

A bridge is not just road infrastructure; it is a structure that exists over rivers and seas.

Therefore, bridge repair is not just about protecting roads and structures. Beneath the bridge, there are rivers and seas, which support fisheries and local life.

For fishery stakeholders, the water environment is their very livelihood. The deterioration of existing coatings on bridges and their falling into the water as paint chips is a significant source of anxiety for the community.

WHiTE Co., Ltd. has received concerns from fishing cooperative officials about the degradation and peeling of conventional solvent-based coatings, the removal of old coatings during recoating, and the scattering and falling of paint chips.

In this context, the WH Series repair proposal—which can be applied over existing fluoropolymer coatings and protects with water-based materials based on SSPC-SP 3—is beginning to be valued not only for extending the life of structures but also from the viewpoints of water environment conservation, consideration for fishery resources, and peace of mind for local residents.

WHiTE Co., Ltd. is proceeding with proposals for repair specifications tailored to the deterioration status and environmental conditions of each site, in consultation with clients, designers, construction companies, and fishery stakeholders for structures near water bodies such as bridges, port facilities, river structures, and fishing port facilities.

## Pursuing Performance Required for Public Infrastructure While Being Water-Based

The WH Series is a repair material that utilizes water-based epoxy technology.

It uses water as a medium to penetrate into the fine pores of concrete and steel, and after the water evaporates, the resin component remains inside the substrate, aiming for integration with the base material.

It is a material that aims to repair, protect, and extend the life of existing structures by penetrating and anchoring within the substrate, not just forming a film on the surface.

The WH Series is used by combining the following materials according to the substrate and deterioration status:
- WH-100: A water-based epoxy primer that penetrates the substrate to consolidate and strengthen fragile parts.
- WH-110: A water-based repair material for forming anti-corrosion, waterproof, and protective layers.
- WH-13: A flexible anionic resin mortar material used for cross-section and defect repair.
- WH Fine Cera Water-based: A water-based topcoat that enhances weather resistance and protection.

By combining these, it addresses multiple repair challenges such as concrete repair, steel anti-corrosion, bridge repair, tunnel lining, water stoppage, waterproofing, and spalling prevention.

## Evidence such as NETIS Registration, NEXCO-related Performance Tests, and Non-combustible Material Certification

The WH Series is undergoing various performance verifications for its use in public works.

The series is registered in the Ministry of Land, Infrastructure, Transport and Tourism's New Technology Information Provision System (NETIS).

It also complies with all 11 items in the NEXCO tunnel lining spalling prevention performance test. The test confirmed performance items required for the repair of tunnels and road structures, such as crack resistance, crack impregnation, chloride ion permeability, and flammability.

Furthermore, performance has been verified by third-party organizations through tests such as non-combustibility tests, accelerated carbonation tests, and weather resistance tests. In the accelerated carbonation test, it was confirmed that the WH-110 treatment contributes to suppressing the progress of carbonation compared to untreated concrete.

These test results allow the WH Series to be proposed as a repair material that aims to achieve both 'environmental consideration by being water-based' and 'the durability and safety required for public infrastructure'.