Water-repellent additives in concrete: types, application

Water-repellent additives are essential for prolonging the life and toughness of concrete. These additives are made to lessen the amount of water that the concrete absorbs, shielding it from moisture-related damage and chemicals that are carried by the water. These additives help keep the reinforcement from corroding, cracking, and spalling by reducing water penetration, ensuring the strength and integrity of the concrete structure over time.

Water-repellent additives come in a variety of forms, each with special qualities and uses. The most popular kinds are crystalline waterproofing agents, silanes, and siloxanes. These additives can be added to the concrete mixture during the pouring process or applied to the finished surface. The project’s particular requirements, the surrounding environment, and the required level of water resistance all play a role in the additive selection process.

Water-repellent additives are easy to apply and can be applied as a surface treatment or during the mixing process. These additives provide uniform protection to the concrete by dispersing evenly throughout the mix after being added. Contrarily, surface treatments form a barrier on the outside of the concrete that keeps water from soaking through. Both techniques work well to lessen water absorption and increase the longevity of concrete buildings.

Water-repellent additives are a proactive measure with long-term benefits when added to concrete construction projects. The resilience and overall performance of the structure are enhanced by these additives, which shield the concrete from damage caused by moisture. In order to increase the longevity and sustainability of concrete, it makes sense to use water-repellent additives for residential, commercial, or industrial uses.

Overview of water repellents

One of the primary characteristics of building materials is their high water absorption due to their porosity. Deeply ingrained in the concrete, moisture weakens the cohesive structure of buildings, aids in the creation of cavities and cracks, and ultimately leads to the collapse of the buildings themselves.

Water-repellent concrete additives create thin films on capillary walls, offering dependable protection to nearly any surface of commercial and industrial buildings against the majority of externally aggravating factors:

• protect against moisture penetration deep into the material;
• improve the thermal insulation properties of surfaces;
• prevent the formation of efflorescence;
• increase the corrosion resistance of structures;
• provide biocidal protection – prevent the growth of lichens and various microorganisms on the surface of products;
• strengthen the structure of the material.

What can I put in concrete to make it water resistant?

Hydrophobic additives in concrete used in modern construction are almost exclusively based on organosilicon polymers (siloxanes) and organosilicon oligomers (silicones). These materials have become industry leaders in the waterproofing of building and structure components due to their low cost and potent ability to mitigate the effects of moisture on concrete structures.

On the other hand, when used in its pure form, a water-repellent addition to concrete serves its intended purpose while also considerably slowing down the hardening process of concrete solutions. Consequently, this kind of additive is typically used in conjunction with other modifiers like plasticizers, hardening accelerators, etc.

Advice: Since the uncontrolled use of water-repellent additives can significantly reduce the density of products, the volume of these additives shouldn’t be greater than the calculated values.

Classification of additives

Concrete water additives vary not only in their chemical makeup but also in how they are applied and how they affect the end product, or the additive’s effect. Three categories of water-repellent concrete additives are distinguished based on their mode of action.

First group

Technical requirements state that the materials in this group must protect structures from moisture and at least five times decrease concrete’s absorption of water.

The reagents listed below represent water-repellent additives for group I concrete:

1. Phenylethoxysiloxane 113-63. Colorless emulsion, insoluble in water. The introduction of this additive helps to increase the mobility of mixtures, but slows down the hardening process and reduces the strength of concrete. Autoclaving of products is not recommended.
2. Hydrophobic additives for concrete based on sodium aluminum methyl siliconate (AMSR-3). These substances are products of the chemical interaction of sodium methyl siliconate and aluminum metal. They are a yellowish or transparent liquid that reacts well with water.
3. Water repellent PlastIL is intended for heavy concrete using Portland slag cement. This additive does not contain chlorides, which contribute to corrosion of reinforcement, increases the plasticity of solutions and reduces the possibility of delamination of mixtures. Available in the form of powder or suspension based on it. Consumption – 1.5% of the total volume of cement.
4. HYDROBETON is a white powder that is added to the concrete dry mix at the stage of concrete preparation. Consumption — 2–3% of the total mass of cement.

Second group

The water absorption of concrete is decreased by 2-4.9 times by all of the group II additives that are presented and utilized to hydrophobize building materials:

• Polyhydrosiloxane 136-41 and 136–157M (GKZh). They are used to increase the hydrophobicity of concrete based on slag Portland cement and pozzolanic Portland cement. At the time of adding these substances, the temperature of the solutions should not be higher than 30°C.

• KOMD-S is an organomineral additive of complex action based on a combination of vegetable oils, sodium nitrite and sulfide-yeast mash. It dissolves well in water. It is characterized by a high plasticizing effect (35–45%).
• Sikalite is a water repellent from the Swiss company Sika. It is a beige powder that is mixed with dry sand-cement mixture. Consumption – 2% of the total volume of cement.

Third group

1. Penazolin sulfate (PSP). Aqueous emulsion or waxy substance of light yellow color.
2. GKZh-11 — sodium methylsiliconate and GKZh-10 — sodium ethylsiliconate GKZh-10. Pale yellow suspensions.

This group of hydrophobic additives reduces a structure’s water absorption by 1.4–1.9 times.

All of the aforementioned materials have the effect of settling on capillary walls and forming the thinnest hydrophobic coatings as a result of a chemical reaction that occurs during cement hydration. Additionally, they create an inverse angle when they come into contact with hydration products, which causes the forces of surface tension to force water out of the pores and onto the structure’s surface.

Biocidal modifiers

In addition to water repellents, biocidal additives are used in concrete to shield building structures from moisture and the growth of pathogenic microorganisms (see photo).

After adhering to the surface of concrete structures, bacteria release organic acids that are caustic during their life cycle. These acids combine with silicates and aluminosilicates to form calcium salts that are soluble in water. Because these compounds are easily removed from the concrete’s structure, the material’s density is lowered, hastening the deconstruction of building structures.

Concrete primers and additives with biocidal properties are made to prevent biochemical corrosion on a structure’s surface.

Special additives can be any of the following categories, depending on the desired outcome:

• bactericidal — protection against the formation of bacteria;
• algicidal — prevent the appearance of algae on the surface of hydraulic structures;
• fungicidal — resist fungal formations.

Concrete surfaces can be protected by the use of organic or inorganic compounds, as well as chemical products derived from them:

• inorganic – salts and oxides of copper, zinc, boron, arsenic, etc.;
• organic – chlorophenols and phenols, compounds of carboxylic, carbamic, oxycarboxylic acids, etc.;
• complex and organoelement compounds of copper, tin, lead, silicon, arsenic, mercury, etc.

By stopping water from penetrating, water-repellent additives in concrete are crucial for increasing the longevity and durability of structures. These additives are available in different forms, each with a specific use: crystalline, silane/siloxane, and polymer-based. Builders can prolong the life of infrastructure and buildings, lower maintenance costs, and guard against water damage by adding these additives to concrete mixtures. It is essential to comprehend the various kinds and their uses in order to choose the appropriate additive to fulfill particular construction requirements.

Concrete additives that repel water have completely changed the way we approach building projects, particularly in damp areas. These additives lessen the chance of damage and stop water from penetrating concrete structures, increasing their longevity and durability. These additives provide a dependable way to preserve structural integrity, whether it’s for a commercial building, a residential basement, or outside infrastructure.

Water-repellent additives come in a variety of forms, each ideal for a particular use case and application. While some are applied as a surface treatment, others are intended to mix right into the concrete, offering comprehensive protection throughout the material. Choosing the best additive for maximum performance will be made easier if you are aware of the particular requirements of your project.

It’s simple to use water-repellent additives and incorporate them into regular construction procedures. They have several advantages, including lower maintenance costs and longer concrete structure lifespans. Concrete maintains its strength and resilience against moisture-related problems such as spalling and cracking, thanks to the additional protection.

For any building project, adding water-repellent additives to your concrete mix is a wise investment. You can get long-lasting, excellent results by making sure your structures are better shielded from water damage. By utilizing these contemporary additives, concrete can become more dependable and resilient, opening the door to safer and more long-lasting structures and infrastructure.

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