By Ben du Preez
HMP’s hydrophobic impregnation solution is a proven concrete protection method. By preventing water ingress into concrete structures, it decreases the likelihood of degradation due to aggressive influences.
It is well known that water damages concrete by moving deleterious agents, such as chloride-ions through the matrix.
Chloride-ions directly attack steel reinforcement. Once they have penetrated concrete, chloride-ions gradually make their way to reinforcing steel. There, they break down the protective layer around the steel causing it to corrode. As rust forms, it expands exerting internal pressure on surrounding concrete. This causes cracking and spalling which weaken structures. If left untreated, foundations, columns and load-bearing components can lose their strength. Refer to Chlorides and concrete. | Concrete Society].
Sulphates also attack concrete. Refer to Overview of Concrete Deterioration Due to Sulphate Attack and Comparison of Its Requirements in International Codes | SpringerLink. By-products of sulphates chip away at the paste that holds aggregates together to form a solid, durable and strong material. As sulphates dry, they form ettringite. These crystals fill the gaps in paste, causing it to break and further damage concrete. Refer to Delayed ettringite formation (DEF) | Concrete Society.
Concrete absorbs water through its capillary structures created when bleed water exits during the curing process. Water, itself, serves as a reaction medium and a reagent in destructive chemical processes especially reinforcing steel corrosion. This leads to the deterioration of concrete cover accelerating exposed reinforcing steel corrosion.
Hydrophobic impregnation concrete protection system
Our hydrophobic impregnation is a non-film forming concrete protection system applied to concrete substrates. Due to the small size of the mono-molecular layer, it does not change the aesthetic appearance of structures.
Unlike film forming coating systems, hydrophobic impregnation penetrates capillaries and lines them internally. By changing the surface tension of mineral substrates, a water-repellent surface is produced. This prevents water and aggressive water-soluble salts from entering concrete.
The surface tension of non-treated mineral substrate is higher than that of liquid water. As such, the attraction from the substrate to the water is also higher than the interaction of water molecules. This is what causes mineral substrates to absorb water.
Hydrophobic impregnation in pores at concrete surfaces reduces surface tension significantly. Therefore, the inter-molecular attraction of water molecules is significantly higher than the attraction of water into the substrates. Water is, thus, repelled by the surface.
The silicone resin network produced achieves an extremely durable bond to most mineral substrates. It is similar to quartz, barring its organic group R, which provides water-repelling properties.
Hydrophobic impregnation’s concrete protection performance
However, hydrophobic impregnation’s concrete protection performance depends on how the contractor applies it. This is a specialist field best left to an experience contractor.
HMP is an approved applicator of an array of hydrophobic impregnation systems manufactured and supplied by reputable companies. They include:
- StonCor Africa | Industrial Coatings, Flooring & Waterproofing Solutions | StonCor Africa
- Mapei – Chemical Products For Building
- a.b.e.® Saint-Gobain • Innovative Construction Chemical Solutions
- Sika South Africa | Construction Chemicals
No two concrete protection projects are ever alike, considering that quality of existing structures varies according to their age and exposure. They also differ in original construction methods, concrete quality and location. There are other factors that also influence the costs of hydrophobic impregnation materials. These include substrate condition, technical requirements, weather conditions, and application methods. Therefore, a detailed condition survey must always be undertaken to optimise the application details and reduce overall costs.
We will first test a suitable solutions and applications on affected areas. This enables us to define the appropriate material and consumption required, in addition to the application method. These factors ensure that HMP achieves the specified performance requirements and can, thus, guarantee our workmanship.
Core samples of the test area allow for analysis of performance of the system and application method. This includes penetration depth and correlating water reduction.
For example, very dense concrete will impede penetration. Therefore, we will select a system that provides a longer penetration time. Consumption will also be higher to achieve the required penetration depth.
Working in hot temperatures and or windy applications, for instance, will result in waste due to increased losses and faster evaporation. Therefore, we would have to choose a suitable solution, such as Sikagard®-706 Thixo.
Hydrophobic impregnation for concrete protection
HMP is an expert in all hydrophobic impregnation system types and applications for sound concrete protection.
Spray application may be faster, but it can also result in higher consumption. Consumption is lower when we apply the system by hand, but this method is slower. It also costs more due to increased labour requirements.
There are two hydrophobic impregnation types, namely liquid and cream. Lower quantities of liquid systems are used for each application step. Therefore, more steps will be required to achieve the defined consumption rate.
Cream types have a longer contact time. However, they penetrate deeper, require less application steps, and provide greater control.
Liquid hydrophobic impregnations are suited to horizontal surfaces, or when deeper penetration is required. They are also ideal for treating large areas or porous surfaces where gravity not an issue. A further benefit is that it can be sprayed evenly across the surface – often in multiple “wet-on-wet” layers. This ensures even absorption.
Cream hydrophobic impregnations are best suited to vertical or overhead surfaces. They are applied with a brush or roller which achieve a thicker consistency. This ensures that the hydrophobic impregnation stays in place longer and achieves deeper penetration over time.
After selecting a suitable system and application, we can determine the necessary quality control and assurance procedures. This will be throughout and after application.
Hydrophobic impregnation – lasting corrosion protection
If undertaken correctly, hydrophobic impregnation will provide a long-lasting corrosion protection solution.
This is considering that hydrophobic impregnations bond chemically to the lining of concrete capillaries where they are not subject to weathering.
Moreover, HMP only uses high quality hydrophobic impregnation systems. When applied at correct coverage rates, they can continue working for 15 years or more without having to be reapplied. Due to their high penetration and extremely thin silicone lining, they rarely change concrete appearance.
South Africa is in the process of adopting European standards for concrete, such as EN 206 and EN 1992. This move could see the local industry also adopt EN 1504. Refer to Repair and Protection in accordance with EN 1504.pdf.
HMP already uses this standard to guide our projects as it provides a structured approach to concrete repair and protection. This spans damage investigation through to the repair and protection systems that we select and how we apply them.
Part 9 details 11 principles and 35 methods for concrete repair and protection. Hydrophobic impregnations align with three principles, namely:
- Principle 1: protection against ingress: keeping concrete dry by reducing its permeability
- Principle 2: moisture control: controlling moisture at acceptable levels
- Principle 8: increasing resistivity: reducing moisture levels to increase electrical resistivity and reduce corrosion risk
Moreover, EN1504 details the specifications of surface protection systems for concrete including hydrophobic impregnations.
Learn more about HMP. www.hindlemason.co.za
Du Preez is Contracts Director of HMP