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1 INTRODUCTION

The durability of reinforced concrete structures

operating in marine environments is a critical concern

in hydraulic engineering. These structures are

continuously exposed to a variety of aggressive factors,

including chloride and sulfate ions, fluctuating

humidity, temperature changes, and cyclic mechanical

and hydrodynamic loads caused by waves, tides, and

currents. Over time, these influences intensify

corrosion processes in both concrete and reinforcement

steel, leading to the progressive deterioration of

structural integrity, reduced load-bearing capacity,

and impaired watertightness. As a result, targeted

repair and strengthening interventions are essential to

maintain functionality and extend service life. Further

discussion on the causes and mechanisms of concrete

degradation in marine conditions can be found in the

following publications: [1], [2], [3], [4], [5], [6].

Most maritime hydraulic structures, such as

breakwaters, quay walls, and piers, function for

Corrosion-Induced Degradation of Marine Reinforced

Concrete Structures: Case Studies from Polish Ports

and Implemented Repair Methods

A. Wawrzyńska

, Tomasz Mioduszewski

& A. Maliszewska

Gdynia Maritime University, Gdynia, Poland

PPBH Aquaprojekt, Gdańsk, Poland

ABSTRACT: Most marine hydraulic structures, such as breakwaters, quay walls, and piers, operate both above

and below the water surface throughout their service life. Maintaining, modernising, or reinforcing these concrete

and reinforced concrete structures, which are in constant contact with seawater, poses a significant engineering

challenge. Ensuring structural performance and operational continuity during repair work is particularly

demanding. This study identifies the main types of environmental impact and the associated mechanisms of

concrete degradation in marine infrastructure, including chemical, physical, and mechanical interactions that

accelerate deterioration. Documented examples of corrosion damage observed in harbour breakwaters, quay

walls, and pier structures are presented, along with proposed repair strategies and their practical implementation.

Photographic documentation illustrates the extent of damage, repair processes, and the final condition of the

renovated elements.

The paper focuses on selected case studies of repair and strengthening works carried out on marine reinforced

concrete structures exposed to the aggressive conditions of the Baltic Sea. The analysed facilities are located in

Polish ports along the Gulf of Gdańsk, with the exact location of each provided in the respective case description.

Each case study includes a detailed account of the applied repair technologies, ranging from surface reprofiling

and polymer-cement coatings to low-pressure crack injection, prefabricated GRC elements, and CFRP

strengthening systems. The findings demonstrate that accurate diagnosis of deterioration processes, combined

with repair strategies tailored to the specific structural type and extent of damage, can effectively mitigate

corrosion, restore structural and operational capacity, and significantly extend the service life of port

infrastructure.

http://www.transnav.eu

the International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 19

Number 3

September 2025

DOI: 10.12716/1001.19.03.25

904

decades under simultaneous exposure to underwater

and atmospheric conditions. Their location in dynamic

marine zones subjects them to constant degradation,

often requiring interventions ranging from routine

maintenance to extensive reconstruction [7]. The most

significant technical challenge in such works lies in

ensuring the structural stability and safety of the

facility during ongoing operations. This is especially

true for commercial port infrastructure, where

downtime may lead to severe economic and logistical

consequences. Because of the diverse and site-specific

nature of environmental impacts and damage

mechanisms, standardized repair protocols are rarely

applicable. Each project demands an individual

approach that considers environmental exposure,

loading conditions, material characteristics of the

original construction, and the type and extent of

damage observed in structural components. A detailed

overview of the degradation mechanisms affecting

concrete in marine environments (including the

influence of chlorides, sulfates, cyclic wetting and

drying, and carbonation) can be found in several

comprehensive publications [1], [3], [8]. Additional

insights specific to port infrastructure and technical

aspects of repair strategies in Polish marine conditions

are discussed by [9], [10], [11] and in relevant national

standards, especially PN-EN 1504 [12], [13], [14], [15],

[16], [17], [18], [19], [20] which is described in detail in

[21].

This study presents selected examples of repair and

strengthening works conducted on marine hydraulic

structures. The described cases demonstrate a range of

engineering solutions tailored to different types of

degradation and environmental constraints. They

highlight the practical challenges involved in repair

execution under marine conditions and evaluate the

long-term effectiveness of the applied techniques in

restoring both functionality and durability.

2 EFFECTS OF SEAWATER ENVIRONMENT ON

THE DURABILITY OF CONCRETE AND

REINFORCED CONCRETE

Marine hydraulic structures are essential components

of port and coastal infrastructure. They facilitate

maritime transportation, protect coastlines, and enable

various economic activities related to shipping,

logistics, and fisheries. Their design and operation

require special consideration of both mechanical loads

and the severe conditions typical of marine

environments such as wave action, tidal fluctuations,

chemical and biological corrosion, and dynamic

hydrodynamic forces [22], [23], [24]. The primary types

of such structures include breakwaters, quay walls,

piers, jetties, and platforms. Breakwaters serve a

protective role by shielding harbour basins from direct

wave impact and coastal erosion. Quay walls are

massive shoreline structures that allow ships to berth

and cargo or passengers to be loaded and unloaded,

they are often integrated with the port’s logistics and

storage facilities. Piers and jetties, which extend into

the water, enable berthing along both sides and

increase handling efficiency. Platforms usually lighter

in design are often used in marinas and small fishing

ports for temporary docking or pedestrian access [24].

Failures and damage to hydraulic structures

(particularly those located in marine environments) are

most often the result of progressive degradation of key

structural components, especially concrete and

reinforcing steel. The primary mechanism of

deterioration is the development of corrosion processes

in marine concrete, often accompanied by

reinforcement corrosion, whose onset and progression

are highly dependent on environmental exposure

conditions as well as material properties and structural

design quality [5], [6].

The durability of marine concrete is affected by a

complex interplay of multiple loads and external

factors. Structural degradation typically results from

the simultaneous influence of mechanical loads,

including self-weight and operational loads (e.g. from

vehicles, cranes, or superstructures), as well as

environmental loads, which are highly variable and

often synergistic. These actions may interact and

accumulate over time, accelerating the degradation

rate and adversely affecting the structure’s stability,

serviceability, and durability [25], [26].

Key environmental loads affecting marine

hydraulic structures polish Baltic sea coast include [27]:

− Sea level fluctuations, typically ranging from

several tens of centimeters to over 150 cm during

extreme events such as storm surges, backwater

effects, or high tides. These fluctuations result in

varying wetting-drying cycles, which facilitate

chloride ingress and carbonation.

− Wind actions, predominantly from the west but also

from periodic northeasterly directions, influencing

wave generation and flow patterns.

− Wave and current-induced effects, including the

transformation of wave parameters (height, length,

period, direction) as they approach the shore. Near-

bottom currents often transport sediments and

contribute to abrasion and erosion of concrete

surfaces [4].

− Ice conditions, particularly in winter months. While

southern Baltic ports do not regularly freeze,

floating or pressure ice may exert dynamic and

mechanical forces on structural elements causing

increased surface wear (ice sheet abrasion).

− High temperature amplitudes, especially daily or

seasonal freeze-thaw cycles near 0°C, which cause

cracking and surface spalling due to internal

expansion of water in concrete pores.

− Hydrostatic pressure and moisture cycles, which

promote the movement and crystallization of

chloride salts within concrete, exacerbating

microstructural degradation [5].

− Physicochemical effects of seawater, including the

presence of aggressive ions such as Cl⁻, Mg²⁺, SO₄²⁻,

and CO₂, which lead to decalcification of the cement

matrix, secondary ettringite formation, and

leaching of calcium hydroxide [6].

− Biological impacts, particularly in coastal zones

with freshwater inflows, where nutrient rich waters

(e.g., containing nitrogen and phosphorus) support

the growth of microorganisms that can accelerate

biodegradation of surface concrete and coatings.

These environmental factors are random in nature,

characterized by continuous variability, often

irregular, sudden, and difficult to predict, and exhibit

both quantitative and qualitative changes over time [7].

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A synthesized classification of such loadings, including

design implications, can be found in reference [8].

Due to the complexity of these effects, the design,

operation, and repair of marine hydraulic structures

require a multidisciplinary and durability-oriented

approach, taking into account not only material

strength but also resistance to long-term

environmental degradation mechanisms.

3 CORROSION MECHANISMS IN CONCRETE

AND REINFORCED CONCRETE UNDER

MARINE ENVIRONMENTAL EXPOSURE

Like other construction materials, concrete undergoes

progressive degradation processes known as

corrosion. This phenomenon encompasses both

chemical and physicochemical mechanisms, as well as

physical processes that contribute to the deterioration

of the material’s structure and properties. Technical

literature distinguishes six primary types of concrete

corrosion: leaching, sulfate, chloride, carbonation, acid,

and magnesium corrosion [9] comprehensively

discussed in sources such as [6-8] [28]. In marine

environments, chloride and sulfate corrosion are of

particular concern due to the high concentrations of Cl⁻

and SO₄²⁻ ions in seawater [28], [29]. It is important to

emphasize that the chemical composition of port

waters is both complex and dynamic. In addition to

naturally occurring salts, these waters may contain

anthropogenic pollutants such as petroleum

hydrocarbons, heavy metals (e.g., Cu, Zn, Pb),

detergents, and biocides. Therefore, when assessing

corrosion risks, the potential occurrence of all known

corrosion mechanisms must be considered.

Concrete exposed to marine environments is

vulnerable to a range of degradation mechanisms, each

of which affects its structure and performance in

different ways. One of the most insidious forms is

leaching corrosion, which typically occurs when

concrete is subjected to prolonged contact with soft

water that contains a low concentration of dissolved

salts. In such conditions, the calcium hydroxide

[Ca(OH)₂] present in the cement matrix becomes

increasingly soluble and is gradually washed out [30].

This leaching process results in higher porosity and a

progressive weakening of the concrete’s internal

structure, a phenomenon often referred to as the "white

death" of concrete due to the characteristic whitening

of affected areas [31].

Carbonation corrosion is another widespread form

of degradation, driven primarily by the presence of

carbon dioxide (CO₂) in both air and water [32]. CO₂

penetrates the porous structure of concrete and reacts

chemically with calcium hydroxide to form calcium

carbonate (CaCO₃). Although CaCO₃ is relatively

stable, the reaction reduces the alkalinity of the

concrete, lowering its pH and thereby compromising

the passive layer that protects embedded steel

reinforcement. Once this protective layer is breached,

the steel becomes susceptible to corrosion. This process

is especially aggressive when the relative humidity

ranges between 40% and 80%, creating ideal conditions

for carbonation [33].

Chloride-induced corrosion poses a particularly

severe threat in coastal or submerged structures, as

chloride ions (Cl⁻) present in seawater are able to

infiltrate concrete via diffusion or capillary action.

Once these ions reach the reinforcement, they disrupt

the passive film on the steel surface, initiating localized

pitting corrosion. This type of degradation is often

accompanied by visible symptoms such as a glossy or

glass, like appearance on the surface and spalling or

detachment of the concrete cover, especially around

the corroding steel [28], [29].

Equally destructive is sulfate corrosion, which

occurs when sulfate ions (SO₄²⁻), also present in marine

and polluted waters, react with the calcium aluminate

phases of hydrated cement. These reactions produce

ettringite and gypsum, both of which are expansive

products. Their formation within the concrete matrix

leads to the development of internal stresses that

ultimately cause cracking, delamination, and structural

disintegration [34].

When concrete is exposed to acidic environments

(pH < 6), it is prone to general acid corrosion. In this

case, acidic solutions dissolve calcium compounds

from the cement matrix, resulting in the formation of

highly soluble salts. The outcome is increase d

porosity, loss of mechanical integrity, and a reduction

in overall durability [27].

Table 2. Types of Concrete Corrosion - Causes and

Reactions; own source based on: [23], [24], [27], [35], [36],

[37], [38]

Types of

Concrete

Detailed Causes

Chemical Reactions

Leeaching

Long-term contact of

concrete with soft water

(low mineral content);

ionic imbalance leads to

dissolution and leaching

of Ca(OH)₂

Ca(OH)₂ → Ca²⁺ + 2OH⁻

(leaching of calcium

hydroxide)

Carbonation

Presence of CO₂ in air or

water under moderate

humidity; CO₂ penetrates

pores and reacts with

Ca(OH)₂.

Ca(OH)₂ + CO₂ → CaCO₃ +

H₂O

(lowering pH of concrete)

Chloride-

induced

High concentration of Cl⁻

ions in seawater;

migration into concrete

and depassivation of steel

reinforcement.

Fe → Fe²⁺ + 2e⁻;

Cl⁻ accelerates localized

corrosion of reinforcing

steel

Sulfate-

induced

Contact with sulfate-

containing solutions

(SO₄²⁻), sulfuric acid, or

gypsum; formation of

ettringite and gypsum

causes expansion.

3 CaO · Al₂O₃ +

3(CaSO₄ · 2H₂O) + 26 H₂O →

3CaO · Al₂O₃ · 3CaSO₄ · 32 H₂O

(ettringite formation)

General

Acid

Exposure to acidic

solutions (e.g., H₂SO₄,

HCl, humic acids); acids

dissolve calcium

compounds forming

soluble salts.

Ca(OH)₂ + 2H⁺ → Ca²⁺ +

2H₂O;

Ca²⁺ + acid anions →

soluble salts

Magnesium-

induced

Ion exchange between

Ca²⁺ and Mg²⁺ from

seawater or deicing

agents; formation of loose

Mg(OH)₂ (brucite) and

breakdown of C-S-H.

Mg²⁺ + 2OH⁻ → Mg(OH)₂

(brucite, structurally weak

product)

Finally, magnesium corrosion is a process that

typically results from long-term exposure to seawater

rich in dissolved magnesium salts or from the use of

deicing agents. It involves the replacement of calcium

ions (Ca²⁺) in the cement paste with magnesium ions

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(Mg²⁺), leading to the precipitation of brucite

(Mg(OH)₂). Unlike calcium-based hydrates, brucite has

no binding properties and forms a weak, porous layer

that further undermines the structural integrity of the

concrete. In the case of quay structures, this

phenomenon is particularly evident in the mooring

path area [27].

4 CORROSION PREVENTION AND THE

IMPORTANCE OF ENVIRONMENTAL

DIAGNOSTICS

In marine environments, various repair techniques are

commonly used to restore and extend the service life of

deteriorated reinforced concrete structures. Among

these, polymer-cement mortars and coatings (PCC) are

widely applied to protect surfaces against

environmental factors such as chlorides and carbon

dioxide. These materials adhere well to existing

concrete, allow water vapor transmission (enabling the

structure to “breathe”), and, depending on the

accessibility of the repaired surfaces, are suitable for

both hand and spray application. Their use is most

effective when the substrate is properly prepared,

although the limited thickness of the applied layers

may restrict their applicability in deeper repairs [39].

Another frequently applied method is shotcreting,

which involves pneumatically spraying concrete or

mortar onto damaged surfaces [40]. This technique is

less time-consuming for repairing large surface areas

and is also effective in zones such as splash regions or

submerged surfaces. It provides excellent compaction

and adhesion but requires specialized equipment and

experienced operators. It may also be less suitable for

small-scale or precision repairs.

For cases involving severe structural degradation,

prefabricated reinforced concrete elements are often

used. These premanufactured components provide

high-quality control, accelerated installation, and high

mechanical strength. However, they typically entail

higher transport and installation costs and require

precise anchoring or integration with the existing

structure.

CFRP (carbon fiber reinforced polymer) systems, in

the form of adhesive-applied strips or mats, are

increasingly used to strengthen elements subjected to

tension or with existing cracking. These composites

exhibit extremely high tensile strength, excellent

chemical resistance, and minimal weight, allowing for

effective strengthening without adding significant

mass. Nevertheless, their application can be limited in

highly humid conditions without adequate surface

preparation [41].

Lastly, low-pressure injection is a repair strategy

focused on sealing and bonding cracks as well as

stabilizing the microstructure of deteriorated concrete.

Using materials such as epoxy resins, polyurethane

gels, or silicate suspensions, these systems are ideal for

preventing water ingress and inhibiting further salt

migration. However, they do not provide significant

structural reinforcement and are best suited for

addressing minor cracks and sealing purposes [41].

Table 3. Comparison of Repair Methods for Reinforced

Concrete Structures - Marine Environment

Repair Method

Application

Advantages

Limitations

Polymer-

Cement Mortars

and Coatings

(PCC)

Surface

protection of

concrete against

environmental

factors; patch

repairs

Good adhesion;

resistance to

chlorides; water

vapor

permeability

Requires

properly

prepared

substrate;

limited layer

thicknes

Shotcreting

Covering large

surfaces in hard-

to-reach areas

(e.g., splash

zone)

High efficiency;

good adhesion;

fast application

Requires

specialized

equipment and

skilled operator;

less effective for

small repairs

Prefabricated

Reinforced

Concrete

Elements

Replacement of

severely

degraded

structural

elements

Controlled

quality; fast

installation; high

strength

High transport

and installation

costs; need for

accurate

anchoring

CFRP

Strengthening

(Strips/Mats)

Strengthening

cracked or

weakened

elements

(beams,

columns, slabs)

Very high

tensile strength;

chemical

resistance; low

weight

Unsuitable for

high humidity

conditions

without surface

preparation

Low-Pressure

Injection

Sealing and

bonding of

cracks;

stabilization of

concrete

microstructure

Precise

application

possible; limits

water and salt

migration

Does not

strengthen the

cross-section

structurally;

limited to minor

cracks

The following sections of this study discuss selected

methods for the repair and strengthening of corroded

structural elements of breakwaters and quays, with an

emphasis on the application of modern material and

technological solutions. The techniques presented

include the use of polymer-cement mortars and

coatings (PCC), shotcreting, prefabricated reinforced

concrete elements, and strengthening systems based on

carbon fiber composite strips.

An integral part of the study is the photographic

documentation, which illustrates typical damage,

repair interventions, and strengthening measures

applied to seaward-facing concrete walls. This

documentation offers readers a unique opportunity to

gain insight into the performance and deterioration of

hydraulic structures operating in harsh marine

environments, particularly from the seaward side,

which is typically inaccessible from within the port

area.

To complement the analysis and provide a clearer

understanding of the technical solutions applied, the

study also includes selected design schematics that

illustrate the adopted repair systems and execution

technologies in a structured and visual format.

5 CASE STUDIES AND THEIR IMPORTANCE

Case studies play a key role in advancing sustainable

construction, offering insight into the real-world

performance of environmentally friendly materials.

They highlight both successes and practical challenges,

such as sourcing, compatibility with existing systems,

or variability in material quality [42]. Take, for

example, the rehabilitation of a reinforced concrete

beam forming part of a mass-handling pier structure.

The pioneering at that time use of carbon fiber strips

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and mats in marine repair work became a reference

point for the development of current design guidelines.

Publishing case studies in scientific journals,

industry reports, and at conferences broadens

knowledge across the sector and builds confidence in

innovative technologies. Well-documented examples

help shape future standards and encourage wider

adoption of sustainable practices. The following six

cases illustrate the long-term performance of

reinforced concrete structures in aggressive marine

environments, their degradation patterns, and the

applied repair and strengthening techniques.

All the cases analysed in this paper are located in

Polish ports on the Gulf of Gdańsk, and their exact

locations are indicated for each case study discussed.

5.1 Case Study 1: North Breakwater, Port Gdynia

A coastal breakwater constructed in the 1920s to shield

harbour basins from open sea exposure was originally

designed as a hybrid structure-featuring a timber

palisade section (approx. 155 meters) and a caisson-

type head segment (approx. 57 meters), totalling 212

meters in length. Over time, it underwent several

modernization phases, including reconstructions in the

1950s and subsequent reinforcements along the

sheltered side in the late 20th century, mostly targeting

the superstructure.

Underwater inspections carried out in the early

2010s revealed significant deterioration, especially on

the seaward side. The timber palisade, topped with a

reinforced concrete cap beam, showed advanced

decay. Its porous configuration, combined with local

material losses, led to migration of the stone backfill,

decreased stability, and wave transmission into

protected basins. Seepage through joints was also

observed, causing water to emerge on the crest, (Fig. 1).

Figure 1. Case study 1, Corroded lower edge of the reinforced

concrete superstructure of the palisade breakwater (on the

seaward side), showing significant concrete losses and

exposed, corroded reinforcement bars in the zone affected by

fluctuating sea levels and wave action, source: own

Corrosion was particularly severe along the tidal

fluctuation zone, where the lower section of the cap

beam exhibited spalling, deep losses, and exposed

timber pile heads-signs of compromised structural

integrity. Experts concluded that due to the extent of

the degradation, partial demolition and

comprehensive repair were necessary.

Figure 2. Case study 1, Cross-section of the North-Eastern

Breakwater - scope of the proposed modernization works

[43]

As a result, a full-scale rehabilitation of the seaward

face of the head section was undertaken in 2012. The

repair involved breaking down the damaged concrete

parapet between +2.20 m and +0.70 m to a depth of 30

cm, followed by the installation of prefabricated

reinforced concrete facing panels and the construction

of a new parapet within this protective shell. The new

parapet was cast from C30/37 concrete and reinforced

with BSt500S ribbed steel bars (ø12 mm and ø16 mm),

with a specified concrete cover of 70 mm. The seaward

wall was formed using prefabricated panels, while the

port-facing side was coated with shotcrete made of

C30/37 concrete, (Fig. 2, Fig. 3).

Figure 3. Case study 1, Left: reconstruction works on the

seaward wall of the North-Eastern Breakwater. Right: view

of the seaward wall of the North-Eastern Breakwater

approximately 12 years after reconstruction. The structure

remains in good technical condition, despite visible signs of

exposure to wave action, fluctuating water levels, and

biological source: own

5.2 Case Study 2: Caisson type North Breakwater, Port

Gdańsk

Constructed between 1972 and 1978, this caisson-type

breakwater, extending approximately 1,625 meters

was designed not only to shield the harbour basins

from direct wave action, but also to dissipate part of the

incoming energy through an innovative reinforced

concrete superstructure. The crest featured a two-part

design: on the seaward side, an expansion chamber

facilitated partial wave energy dispersion, while the

port-facing section incorporated a high, curved parapet

designed to reflect overtopping waves and provide

access for maintenance.

After more than forty years of continuous service, a

condition survey conducted in 2015 identified

significant deterioration, despite earlier localized

repairs. The most critical issues included the poor state

of the expansion chamber surface, exposed and

corroded reinforcement in the parapet crest, cracked

and unsealed joints between caisson units, structural

gaps, and visible damage to the prefabricated

deflectors mounted in the expansion zone. Out of the

thirty such elements, many showed signs of advanced

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corrosion despite having undergone previous

maintenance interventions, (Fig. 4-6).

Figure 4. Case study 2, View of the expansion chamber from

the bay side: visible surface damage to the wave deflectors

and exposed reinforcement of the breakwater parapet,

source: own

Figure 5. Case study 2, View of the expansion chamber from

the bay side: visible damage to the superstructure (exposed

reinforcement) and wave deflectors, as well as rust stains

caused by reinforcement corrosion and concrete loss in the

area of the structural expansion joints, source: own

Figure 6. Case study 2, View from the expansion chamber;

visible surface damage to the breakwater parapet following

previously conducted repairs, source: own

Although the core function of the breakwater

protecting the harbour remained intact, a

comprehensive repair program was deemed necessary

to preserve its operational performance. The remedial

strategy involved the installation of prefabricated glass

fiber reinforced concrete (GRC) components to shield

the parapet crown, combined with polymer-modified

shotcrete reinforced with alkali-resistant fibers to

restore the surfaces. In areas adjacent to port

infrastructure, the parapet was elevated to +4.90 meters

above sea level, with new reinforced ribs introduced at

regular intervals to support the additional height. The

expansion chamber surface was rebuilt using an 8 cm

thick overlay of polymer-modified concrete, also

reinforced with fiberglass and treated with a

hydrophobic sealant to enhance durability.

Furthermore, both the seaward and port-facing cap

beams were reinforced with cast-in-place concrete

jackets, protected by precast facing panels (Fig. 7).

Figure 7. Case study 2, Typical cross-section of the Northern

Island Breakwater within the scope of repair works [44]

Together, these interventions not only addressed

the structural and material deficiencies but also

extended the overall service life of the breakwater,

ensuring continued protection of the port against

marine forces.

Figure 8. Case study 2, Left: Repair works on the seaward

wall of the Northern Island Breakwater.

Right: View of the repaired parapet of the Northern Island

Breakwater from the inner side visible shotcrete coating on

the parapet and surface sealing with spray applied polymer-

cement coatings, source: own

The photograph (Fig. 8 left) shows the removal of

the reinforced concrete parapet and the surface layer of

the expansion chamber down to sound concrete, as

well as the application of polymer-cement mortar. In

contrast to the previously described repair works on

another (Case 1) breakwater structure, this case allows

for the evaluation of the superstructure repair only, as

the intervention was completed just a few months ago

(Figs. 8 right). Despite the short time since completion,

initial signs of biological growth are already visible at

the tidal fluctuation zone, indicating the beginning of

natural environmental interaction with the renovated

surface.

5.3 Case Study 3: Caisson quay structure, Port Gdańsk

The quay, constructed in the 1970s, is based on

prefabricated reinforced concrete caissons topped with

a trapezoidal coping beam forming the superstructure.

After over fifty years of service in harsh marine

conditions, significant deterioration of the concrete

surface was observed, particularly in the tidal zone. In

several locations, reinforcement was exposed due to

delamination of the concrete cover, leading to localized

corrosion and structural concerns.

To address these issues, a targeted repair program

was implemented, focusing exclusively on the concrete

elements of the superstructure (Fig. 9). The damaged

concrete was carefully removed, reinforcement was

cleaned and coated with a corrosion inhibiting primer,

and reprofiling was performed using polymer-

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modified PCC mortars classified as R4 according to EN

1504. To protect the lower edge of the coping beam

from ice abrasion, L-shaped GRC prefabricated

elements were installed along the quay wall-20×20 cm

in standard areas and 20×80 cm at the low quay section

recesses where access ladders were located. The

selected materials ensured resistance to chlorides,

seawater, frost cycles, and mechanical impact. Final

surface finishing included sealing with flexible

polymer-cement coatings and injecting PCC mortar

between the GRC panels and the original concrete to

create a durable, cohesive repair system suitable for

long-term exposure in a marine environment (Fig. 10,

11).

Figure 9. Case study 3, Condition of the quay and capping

beam before the 2018 renovation, with close up views of the

damaged elements shown on the right, source: own

Figure 10. Case study 3, Fender line replacement project:

close up view shows the designed surface reprofiling using

PCC mortars and the proposed GRC prefabricated element

protecting the lower edge of the quay superstructure.

Platform modernization project: coloured elements indicate

components designated for repair; a detailed view is shown

on the right [45]

Figure 11. Case study 3, View of the modernized structure

after reconstruction, source: own

5.4 Case Study 4: Access platform, Port Gdańsk

Case 4 concerns the renovation of a reinforced concrete

access platform and approach walkway leading to a

port berth, originally constructed in the 1980s. The

structures, consisting of precast prestressed beams

supported by reinforced concrete pile caps on

prefabricated piles, had been in continuous use for

over thirty years under severe marine conditions.

Prolonged exposure to saltwater, temperature changes,

and heavy use led to advanced degradation of

concrete, reinforcement corrosion, and damage to the

steel bearings supporting the spans (Fig. 12).

Based on a prior technical assessment, a

comprehensive repair project was developed. The

scope of work included reprofiling and waterproofing

of the top and side surfaces of the pile caps, patching

and sealing cracks and defects in the precast beams,

replacement of corroded steel bearings with

elastomeric types, application of anticorrosion coatings

to steel components, and the installation of protective

surface systems on areas vulnerable to moisture and

environmental exposure. The project employed a

variety of advanced materials, including PCC repair

mortars, dry spray shotcrete, epoxy-based compounds,

low-shrinkage and expansive grouts, and flexible

protective coatings. Waterproof PVC membrane

expansion joints were also installed to ensure tightness

and structural durability (Fig. 13).

Work was conducted in phases using suspended

scaffolding and temporary supports, allowing parts of

the installation to remain in service during the

renovation. The adopted technologies and material

solutions restored the structural integrity and

serviceability of the platform, extending its operational

life for decades to come (Fig. 14).

Figure 12. Case study 4, Condition of the platform before

renovation Visible severe damage to both fixed and

unidirectional sliding bearings. Extensive corrosion is

observed on both steel and elastomeric components. Bearing

pedestals are heavily degraded, with numerous cracks,

material losses, and spalling, source: own

Figure 13. Case study 4, Platform modernization project,

with the elements designated for renovation marked in

colour; a structural detail is visible on the right side [46]

910

Figure 14. Case study 4, Condition of the platform after

renovation, source: own

5.5 Case Study 5: Port Authority Quay, Port Gdańsk

The project concerned the renovation of a section of a

berthing quay constructed in 1974, used primarily for

tug operations. The objective was to replace the

obsolete fender line and refurbish the mooring

walkway to meet current operational requirements.

The jetty type structure, supported on three rows of

prefabricated reinforced concrete piles, included a rear

steel sheet pile wall anchored with rock fill (Fig. 15).

The scope of works included dismantling of existing

fender units and walkway components, construction of

a new reinforced concrete coping wall, and installation

of point type fender systems using rubber beams with

steel stiffeners. The outer edge of the walkway was

protected with L-shaped GRC prefabricated elements,

and the paved surface was designed in compliance

with maritime construction regulations. Mooring

bollard blocks were replaced, and coping wall

extensions were added at fender locations. The work

was divided into three stages to maintain berthing

capacity for four tugs throughout the rehabilitation

(Fig. 16, 17).

Figure 15. Case study 5, Quay ccondition before renovation,

showing significant concrete losses and exposed, corroded

reinforcement wall, source: own

Figure 16. Case study 5, Project for the renovation of the

mooring and fender line, including the proposed GRC

prefabricated element [47]

Figure 17. Case study 5, View of the mooring and fender line

after reconstruction, with the GRC prefabricated element

visible on the quay wall, source: own

5.6 Case Study 6: Reinforced Pier, Port Gdańsk

After more than 30 years of service in a harsh marine

environment, one of the reinforced concrete pier

structures supporting mass loading equipment

showed serious signs of structural fatigue. Cracking

near supports, delamination of reinforcement cover,

and general material degradation led to an urgent

decision to carry out repairs and structural

strengthening (Fig. 18).

The chosen solution involved reprofiling the

damaged concrete beams and applying external carbon

fiber reinforcement. Carbon fiber mats and strips were

bonded with epoxy resins to restore load bearing

capacity. This method, widely used in structural

engineering, offers high tensile strength, corrosion

resistance, and allows work to be conducted without

heavy equipment. Repairs were performed using

suspended scaffolding, with the affected section

temporarily closed during works. Other areas of the

terminal remained operational. The method proved

technologically efficient and economically viable.

Thanks to the durability of carbon fiber composites, the

reinforced structure is expected to continue

functioning reliably for many years (Fig. 19-23).

911

Figure 18. Case study 6, Bottom layer of the beam - visible

delamination of the reinforcement cover, exposed reinforcing

bars, source: own

Figure 19. Case study 6, Locations of damage according to

preliminary design tests, [48], [49]

Figure 20. Case study 6, Left: after removal of loose or poorly

bonded concrete fragments; all reinforcement bars of the

bottom layer are visible. Right: the same element during

repair - application and anchoring of carbon fiber tapes,

source: own

Figure 21. Case study 6, Designed reprofiling and

strengthening of crane support beams [49]

Figure 22. Case study 6, Placing carbon mats and tapes with

one prefabricated crane beam [48], [49]

Figure 23. Case study 6, Application and anchoring of carbon

fiber mats, source: own

6 DISCUSSION OF CASE STUDIES FURTHER

RECOMMENDATIONS

The case studies presented illustrate the diverse nature

of concrete and reinforced concrete degradation in

marine environments, as well as the wide range of

220cm

130cm

220cm

100cm 180cm

20cm

1140cm

94cm 185cm 460cm 345cm

56cm

110cm

220cm

180cm

20cm

Przekrój 3-3Przekrój 2-2Przekrój 1-1

49cm

45cm

95cm

105cm

85cm

60cm

strefa

występowania rys

strefa

występowania rys

strefa występowania

rys wytężeniowych

strefa

występowania

rys wytężeniowych

strefa występowania

rys wytężeniowych

strefa występowania

rys wytężeniowych

odspojona otulina

zbrojenia na

narożnikach

środnika belki

odspojona otulina zbrojenia

na narożnikach środnika belki

odspojona otulina zbrojenia

na narożnikach środnika belki

strefa występowania rys

oś uciąglonej belki

dwuprzęsłowej

torowiska ładowarek

strefa odspojenia

otuliny zbrojenia

oś uciąglonej belki

dwuprzęsłowej

torowiska ładowarek

Przekroje poprzeczne

Widok z boku

Widok od dołu

1. oczyszczone pręty zbrojenia zabezpieczyć warstwą materiału SIKA TOP

ARMATEC 110 EPOCEM

2. warstwa sczepna SIKA TOP ARMATEC 110 EPOCEM

3. gotowa zaprawa torkretowa SIKA GUNIT 03 Normal lub Rapid

z dodatkiem materiału zawierającego migrujące inhibitory korozji

FERROGARD 903 (na spodzie belek zastosować siatkę stalową 10x10cm Ø5mm

połączoną z odkrytym i zabezpieczonym zbrojeniem)

4. warstwa wyrównująca o grubości ok. 5 mm, lokalnie do 10 mm (w porach)

- SIKADUR 41

5. klej epoksydowy SIKADUR 30

6. taśma z włóknami węglowymi

7. warstwa kleju z posypką z piasku kwarcowego

8. powłoka ochronna na całej powierzchni belki - SIKAGARD 550 Elastic

po uprzednim zamknięciu porów szpachlówką SIKAGARD 720 EPOCEM

1. warstwa sczepna SIKA TOP ARMATEC 110 EPOCEM

2. gotowa zaprawa SIKA MONOTOP 612/614

3. warstwa wyrównująca o grubości ok. 5 mm, lokalnie do 10 mm (w porach)

- SIKADUR 41

4. klej epoksydowy SIKADUR 30

5. taśma z włóknami węglowymi

6. warstwa kleju z posypką z piasku kwarcowego

7. warstwa kleju epoksydowego SIKADUR 330

8. mata z włóknami węglowymi SikaWrap 200 C

9. warstwa kleju z posypka z piasku kwarcowego

10. powłoka ochronna na całej powierzchni belki - SIKAGARD 550 Elastic

po uprzednim zamknięciu porów szpachlówką SIKAGARD 720 EPOCEM

Reprofilacja dolnej części belki

Naprawy płytkie (w miejscu klejenia mat SikaWrap)

Reprofilacja dolnej części belki

Naprawy głębokie (odsłonięte zbrojenie)

100cm

siatka stalowa 10x10cm

z pręta Ø5mm

wypełnienie przestrzeni

klejem SIKADUR 30

1. powłoka ochronna na całej powierzchni belki -

SIKAGARD 550 Elastic po uprzednim zamknięciu

porów szpachlówką SIKAGARD 720 EPOCEM

1. wyrównanie szpachlówką SIKAGARD 720

EPOCEM, układaną warstwą o grubości 2 mm

2. gruntująca żywica epoksydowa SIKAFLOOR 156

3. nawierzchnia z żywicy

epoksydowo-poliuretanowej zmieszanej z

piaskiem kwarcowym ICOSIT ELASTOMASTIC TF

Reprofilacja górnej części belki

listwy drewniane

pozostające w

kapinosach z czasów

budowy usunąć

zapewniając poprawną

pracę kapinosa

istn szyna poddźwigowa SD-100

wraz z mocowaniem na blasze ślizgowej

istn. zbrojenie podlewki szyny

38cm

220cm

100cm

oś uciąglonej

krawędź prefabrykatu

uciągleniePref. żelb. belka torowiska ładowarek nr 8

taśma kompozytowa na bazie

żywic epoksydowych z włóknami

węglowymi Sika CarboDur S1214

szerokości 120 mm i grubości 1.4mm

mata z włóknami węglowymi SikaWrap 200C

szer. 300 mm, ułożona w 7 warstwach

oś dodatkowej

mata z włóknami węglowymi SikaWrap 200C

szer. 300 mm, ułożona w 5 warstwach

mata z włóknami węglowymi SikaWrap 200C

szer. 300 mm, ułożona w 4 warstwach

mata z włóknami węglowymi SikaWrap 200C

szer. 300 mm, ułożona w 2 warstwach

mata z włóknami węglowymi SikaWrap 200C

szer. 300 mm, ułożona w 1 warstwie

mata z włóknami węglowymi SikaWrap 200C

szer. 300 mm, ułożona w 1 warstwie

mata z włóknami węglowymi SikaWrap 200C

szer. 300 mm, ułożona w 2 warstwach

mata z włóknami węglowymi SikaWrap 200C

szer. 300 mm, ułożona w 3 warstwach

belki dwuprzęsłowej

podpory

Widok z boku

Widok z dołu

matami oraz taśmami z włóknami węglowymi

Projektowane wzmocnienie pref. żelb. belek torowiska ładowarek

Pref. żelb. belka torowiska ładowarek nr 7

oś dodatkowej

podpory

taśma kompozytowa na bazie żywic epoksydowych

z włóknami węglowymi Sika CarboDur S1214

szerokości 120 mm i grubości 1.4mm

proj. płaskowniki kotwiące

proj. kotwy wklejane M16

blacha łożyska

ślizgowego

mata z włóknami węglowymi SikaWrap 200C

szer. 300 mm, ułożona w 6 warstwach

912

remedial approaches used to address such damage. A

key commonality among all the analyzed structures is

their long-term service under harsh conditions

including water level fluctuations, salinity and

humidity, and cyclic loads induced by vessel traffic

and wave action. These aggressive factors contributed

to gradual deterioration in each case, necessitating

timely intervention. In older structures (for example,

early 20th century breakwaters), degradation was

mostly confined to the concrete superstructures,

parapets, and the outer concrete cover protecting the

rebar. Repairs in these instances typically involved

surface reprofiling and sealing of relatively shallow

defects to restore the protective cover. In contrast, more

complex or heavily loaded structures such as

reinforced concrete crane beam slabs or access

platforms experienced damage not only to the outer

concrete layers but also to the primary load-bearing

elements. These severe cases required more advanced

repair technologies to restore structural capacity.

Notably, one rehabilitation project involving the

external strengthening of crane rail beams with CFRP

(carbon fiber reinforced polymer) strips and mats stood

out as an innovative solution, and it has since become

a reference point for similar works. Other cases

employed glass fiber reinforced concrete (GRC)

prefabricated elements to protect exposed edges,

specialized anticorrosion treatments and low-

shrinkage grout for bearing supports, as well as

multistage repair works carried out under ongoing

port operations to minimize downtime. This breadth of

techniques demonstrates the importance of choosing

repair strategies tailored to the specific failure

mechanisms and operational constraints of each

structure. As summarized in the comparative analysis

table (see Table 4), the effectiveness of a given

rehabilitation approach depended not only on the

material properties of the repair products but also on

practical aspects of execution, for instance, staging of

works to ensure continued quay availability, the

accessibility of damaged zones, and underlying

foundation at the site. Notably, in most cases the

applied repair solutions enabled the facilities to remain

in long-term use with no further deterioration

observed in the rehabilitated areas. This confirms that

the chosen interventions were generally successful in

arresting damage and prolonging the service life of the

structures.

The presented cases illustrate a wide range of

degradation mechanisms and repair strategies for

marine concrete structures. As demonstrated in the

comparative table (see above), the chosen techniques

were specifically adapted to the structure type, extent

of damage, and operational constraints. Older

structures (Cases 1-3) were primarily affected by

surface level concrete deterioration and rebar

corrosion, particularly in splash zones or at the

interfaces of prefabricated elements. Their

rehabilitation focused on reprofiling, the use of GRC

prefabricated elements, and protective surface

coatings. In contrast, more recent and complex

structures (Cases 4-6) required advanced methods such

as elastomeric bearing replacement, polymer-cement

based reprofiling, and composite CFRP strengthening

of load bearing members. Particularly noteworthy was

Case 6, the Reinforced Pier, where the external

strengthening of reinforced concrete beams using

carbon fiber composites was an innovative solution at

the time. This approach became a reference model for

subsequent reinforcement projects in marine

environments, demonstrating that well designed

strengthening (without unnecessary major

reconstruction) can extend service life significantly,

even for structures showing critical signs of structural

fatigue.

Overall, the analysis confirms that successful

rehabilitation of marine concrete structures requires

not only knowledge of material technologies but, more

importantly, a tailored engineering approach. Each

intervention must take into account the structure’s

operational history, accessibility, loading conditions,

and environmental exposure in order to achieve long-

term durability and performance.

Table 4. Comparative Table of Rehabilitation Case Studies

for Marine Hydrotechnical Structures

Case Study

Type of

Degradation

Scope of Repair

Works

Applied

Technologies

Breakwater

Constructed

in the 1920s

Cap corrosion,

concrete losses,

timber

degradation,

rockfill

migration

Partial

demolition, RC

panels

installation, new

parapet

RC prefabs,

C30/37

concrete, dry-

mix shotcrete

Caisson-type

Breakwater

Rebar corrosion,

cracks, leakage,

baffle damage

Chamber

reconstruction,

shotcrete, prefabs,

protective

coatings

GRC, polymer

concrete,

reinforced

shotcrete

Caisson

Quay

Structure

Cover

delamination,

rebar corrosion,

tidal

degradation

Cleaning, PCC

repairs, edge

protection

installation

PCC R4, GRC

prefabs,

flexible surface

coatings

Access

Platform

Bearing

corrosion,

concrete loss,

damage to piers

and spans

Reprofiling,

bearing

replacement,

waterproofing,

joint repairs

PCC, injection,

protective mats

and coatings

Port

Authority

Quay

Equipment

damage,

concrete

degradation,

corrosion

Demolition, new

mooring path,

fenders, prefabs,

new bollard

blocks

GRC, rubber

fender beams,

C35/45

concrete,

anchors

Reinforced

Pier

Support

cracking, cover

delamination,

rebar corrosion

Reprofiling,

external CFRP

strengthening,

anchoring

CFRP strips

and mats,

epoxy

adhesives

Based on the conducted analysis and case studies,

the following recommendations can be formulated for

the design and implementation of repair works for

concrete and reinforced concrete hydraulic structures

operating in marine environments:

1. Early damage diagnosis should be an integral part

of maintenance strategies, enabling repair

interventions before critical structural deterioration

occurs.

2. Selection of repair technologies must be preceded

by thorough assessment of environmental

exposure, access limitations, and site specific

operational constraints.

3. In cases of structural damage, external

strengthening using CFRP composites can be a

highly effective alternative to traditional methods

provided the system is properly designed and

anchored.

4. GRC prefabricated elements are well suited for use

in impact zones and should be considered in

913

rehabilitation projects involving ice or mechanical

wear.

5. For facilities operating continuously, staged

construction and minimal disruption to service are

essential to ensure uninterrupted port functionality.

6. It is recommended to maintain detailed repair

documentation that captures materials used,

techniques applied, and technical outcomes, thus

facilitating knowledge transfer for future retrofit

projects.

7 CONCLUSIONS

Most marine hydraulic structures operate both above

and below the water surface throughout their long

service life. Repairs, local refurbishments, large scale

modernisations, reconstructions, and structural

reinforcements represent an ongoing challenge for

hydraulic engineers. The most demanding projects are

those in which it is necessary to ensure the stability of

the structure during the repair process while also

maintaining operational continuity or readiness of the

facility.

In the case of marine structures, it is difficult to

speak of standard repairs or renovations. Each facility

is treated individually, taking into account

environmental factors, the types of loads acting on the

structure, the materials used in the original

construction, and, above all, the type and extent of

damage to individual components. Typically, failures

and damage in hydraulic structures are caused by the

corrosion of marine concrete or the degradation of

other key load bearing elements. The durability of

marine concrete is determined by damage resulting

from the simultaneous action of self-weight,

operational loads, and environmental influences such

as chloride ingress, sustained high humidity,

temperature fluctuations, dynamic loading from wave

action and cargo-handling operations, and cyclic

wetting and drying. These destructive factors often act

synergistically, leading to carbonation, reinforcement

corrosion, cracking, delamination of the concrete cover,

and, ultimately, loss of structural capacity and water

tightness.

The case studies analysed in this paper confirm that

successful rehabilitation of marine structures is

achievable through accurate identification of

degradation mechanisms and the application of repair

technologies tailored to the specific type of structure

and extent of damage. For older structures, the primary

measures included surface reprofiling, crack sealing,

application of protective coatings, and the installation

of prefabricated GRC panels. More complex and

heavily loaded facilities required advanced techniques

such as polymer-cement concrete (PCC) reprofiling,

elastomeric bearing replacement, low pressure crack

injection, and external strengthening with CFRP

composites. Of particular significance was the

strengthening of crane rail beams at the reinforced

handling pier using carbon fibre strips and mats, a

pioneering solution at the time, which has since

become a reference model for subsequent marine

rehabilitation projects. The comparative analysis

shows that the effectiveness of selected repair

technologies depended not only on material

performance but also on foundation conditions, repair

staging, and accessibility to the damaged components.

In all six documented cases, the adopted repair

strategies successfully restored both the structural

integrity and operational capacity of the facilities, with

no recurrence of damage observed in the rehabilitated

areas. These findings demonstrate that effective

rehabilitation of marine concrete infrastructure

requires more than knowledge of materials; it demands

a comprehensive engineering approach that takes into

account operational history, environmental exposure,

loading regimes, and site-specific constraints. When

executed correctly, such interventions can successfully

mitigate the effects of corrosion and significantly

extend the safe service life of critical port and coastal

infrastructure.

ACKNOWLEDGEMENTS

The paper presents results developed in the scope of the

research project number WN/2025/PZ/10, granted by GMU

in 2025.

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