Concrete degradation mechanisms – and how the right protection extends service life

Concrete is often perceived as a robust and maintenance-free material, but in reality, it is constantly exposed to moisture, chemical attack, and environmental stress that gradually break down its structure. Due to its porous composition, harmful substances such as water, chlorides, carbon dioxide, and acids can penetrate and cause deterioration, carbonation, frost damage, and reinforcement corrosion.

To preserve the durability of concrete, protection is needed that not only blocks moisture – but also allows the material to breathe.

Impregnation penetrates deep into the concrete and creates an integrated, crystalline barrier that strengthens the structure, raises the pH level, and blocks water and gas ingress. It is particularly effective against carbonation, acid attack, and frost-related damage.

Hydrophobization forms a water-repellent surface that prevents rain, dirt, and pollutants from penetrating, while allowing moisture to evaporate from within. This makes it an ideal surface protection – especially where a traditional vapor barrier is missing.

Depending on the conditions, impregnation and hydrophobization – individually or combined – provide a breathable protection system that extends the structure’s service life, reduces maintenance needs, and preserves the concrete’s original strength and appearance over time.

Water – carrier of harmful substances

Water is the main carrier of harmful substances such as chlorides, sulfates, and acids. These dissolve the concrete’s binder (calcium leaching), lower the pH, and cause reinforcement corrosion. Over time, the structure weakens and loses its strength.

Impregnation penetrates deep into the concrete, raises the pH, strengthens the binder, and forms crystals that effectively block further water ingress – while still allowing moisture to evaporate outward.

Hydrophobization creates a water-repellent surface that protects against rain and moisture penetration while allowing the concrete to “breathe” by letting internal moisture evaporate.

Carbonation – CO₂ and corrosion risk

Carbon dioxide in the air reacts with moisture and calcium hydroxide in the concrete to form calcium carbonate – a process known as carbonation. This reduces the pH from around 12–13 to below 9.5. When the pH drops, the reinforcement loses its natural passive protection and begins to corrode, leading to cracking and reduced durability over time.

Impregnation penetrates deep into the concrete and forms a dense, crystalline structure that effectively stops the ingress of both water and carbon dioxide. By maintaining a high pH, the reinforcement is protected from corrosion and the carbonation rate is significantly slowed.

Hydrophobization creates a water-repellent surface that prevents moisture from penetrating – and since carbonation requires both CO₂ and moisture, this treatment further reduces the risk. The concrete remains dry, preserving its alkaline environment and resistance to corrosion.

Frost – the hidden force that cracks concrete

When water freezes inside the concrete, it expands by about 9% in volume, creating internal stresses and cracks. Repeated freeze–thaw cycles worsen the damage over time, especially in the presence of salts. Salts lower the freezing point and cause more frequent freezing and thawing, which increases the risk of degradation and surface scaling.

Impregnation penetrates into the concrete and blocks the capillaries, preventing water from accumulating and freezing inside the material.

Hydrophobization creates a water-repellent surface that reduces moisture uptake and thereby minimizes the risk of frost-related damage.

Efflorescence – white deposits from within

White stains or crystalline deposits on concrete surfaces are usually caused by moisture dissolving calcium hydroxide in the cement paste and transporting it to the surface through capillaries. As the water evaporates, the calcium reacts with carbon dioxide in the air to form calcium carbonate – a process known as efflorescence. It is a visible sign of ongoing moisture movement and leaching of the binder.

Impregnation penetrates deep into the concrete, binds calcium within its structure, and blocks capillary transport of moisture. This effectively stops efflorescence formation and contributes to a more stable and durable surface.

Hydrophobization creates a water-repellent surface that prevents rain and external moisture from entering. By keeping the concrete drier, internal moisture flow is reduced, further limiting efflorescence and preserving a clean, even surface over time.

ASR – Alkali–silica reaction

ASR occurs when reactive silica-rich aggregates react with alkalis in the cement paste and form a gel-like product. This gel expands in the presence of moisture, creating internal stresses that lead to cracking and gradual deterioration of the concrete. Since the reaction is linked to material selection, there is no complete solution once the damage has started – only measures that can slow the process.

Impregnation should not be used on structures where ASR occurs or is suspected, as it may raise the local alkali concentration in the concrete. In some cases, this can accelerate the reaction and worsen the damage.

Hydrophobization is a safe and effective measure. By creating a water-repellent surface, it reduces the moisture ingress required for the ASR gel to expand. This slows the reaction process and significantly reduces the risk of new cracking.

Acid attack – air pollution and acid rain

Airborne sulfur dioxide (SO₂) reacts with water and oxygen to form sulfuric acid. This acid attacks the cement paste binder and converts it to calcium sulfate (gypsum). A surface layer may form that appears protective at first, but degradation continues beneath the surface, gradually weakening the concrete. Acid attack often results from industrial emissions, acid rain, or biological activity in moist environments.

Impregnation penetrates deep into the concrete, raises the pH, and creates a long-lasting, acid-resistant barrier within the structure. It blocks water ingress and establishes an alkaline environment that prevents further chemical degradation and inhibits the growth of moss and algae.

Hydrophobization protects the concrete surface by repelling rainwater and preventing polluted moisture from entering. By keeping the surface dry, it reduces the formation of acids that attack the binder, preserving both the appearance and the strength of the concrete over time.

Impermeable coatings – risk when vapor barrier is missing

Bitumen, epoxy, and other impermeable coatings effectively prevent water from penetrating from above on ground-supported slabs. However, if there is no functional vapor barrier beneath the structure, ground moisture can rise and become trapped under the coating. The resulting vapor pressure can cause blistering, delamination, or detachment of the surface layer. If the coating is damaged, moisture and chlorides can penetrate beneath it, accelerating the degradation of both concrete and reinforcement.

Impregnation creates a deep-acting, breathable barrier within the concrete. It resists impact and wear, tolerates rising moisture, and allows the structure to release vapor without building pressure. This makes it particularly suitable for buildings where no vapor barrier is present or where it is insufficient.

Hydrophobization forms a water-repellent surface that protects against rain and spills from above while allowing moisture to diffuse outward. The combination of impregnation and hydrophobization provides a durable, moisture-safe system that preserves the function and appearance of the concrete without trapping moisture.