Silicon-based technology for the protection of construction material

Dow Corning Corporation is a leader in developing new Silicon-Based Technologies (SBTs) that advance the construction industry and empower formulators to offer new functionality in various applications.

Products are available for use in a wide range of construction applications, including:

• penetrating coatings for the treatment of structural concrete
• anti-stain coatings to protect concrete and masonry surfaces
• injection material against rising damp
• primers
• silicone resin emulsion for improved architectural coating
• fiber reinforced cement board admixture or sealer
• gypsum board hydrophobic treatment
• antifoam for paint or cementitious mixture
• demolding oil
• admixture for mortar or dry mix

These products are commonly used to impart enhanced durability and performance attributes in construction materials. They are available as:

• ready to use coatings,
• primary intermediates for a formulation, or
• additive materials for formulations.

SBTs provide characteristics and performance attributes not found in traditional organic additives. Formulators use SBTs to differentiate their products and offer functionality for specific market needs. These include the need for greater resistance to water; enhanced weatherability; and improved long-term durability in demanding environments. SBTs provide utility as both ready to use treatment as well as at very low-use levels as additives. Finally, many silicon materials combine easily with organic products and polymers, allowing formulators to develop specialized blends with the functionality of both organic and non-organic materials.

To fully understand the importance of SBTs to the construction industry, formulators need to know what raw material options are available and the properties they impart in selected applications. A wide range of silicon-based chemistries have been used for decades in construction applications, and are now the cornerstones of new research and product development.

Silanes

Silanes are monomeric materials containing one silicon atom (Figure 1). They are often used as such to treat concrete or blended with other silicon based components to formulate water repellent dispersion or emulsion.

Silanes react with inorganic reactive groups (e.g. found in cementitious substrates or bricks) and release methanol or ethanol (group R1, R2 or R3 in figure 1) upon reaction. This reaction chemically fixes the silane on the construction material. The non-reactive groups which is left on the silane (R4 group in figure 1 can be methyl, propyl, isobutyl or octyl alkyl chain) provides moisture resistance to the construction material.

The chemical anchorage of the silanes makes them suitable for use in water-repellent formulations that demand greater UV-stable protection of masonry substrates, including concrete, sandstone, limestone, brick, tile and perlite.

Alkoxysilanes are widely recognized as adequate technical solutions to protect concrete against water penetration, chloride ingress and the associate rebar corrosion. Impregnation hydrophobic treatments based on silanes are still enabling the concrete to breath as silanes treat the surface of the pores but are not blocking the pores themselves. Their low viscosity and low molecular size enable deep penetration into the concrete surface, providing long term protection.

For example, Dow Corning® Z-2306 (silane IBTMS) is a proven material to protect concrete structure. It prevents degradation of the reinforced concrete by corrosion, caused by salt water spray and wet conditions. Several infrastructures have been protected using Dow Corning silanes around the world.

Polydimethylsiloxane (PDMS)

PDMS is a colorless silicon-based polymer used across many different industries, primarily for its hydrophobic properties (Figure 2). In construction material protection, it imparts mainly protection against water or foam control.

Included in water repellent formulation, it provides good protection against water ingress and good beading.

For example, Dow Corning® IE-6683 Water Repellent is a 40% active, water-dilutable silicone emulsion, including some polydimehtylsiloxane fluid, used to provide water repellency to porous construction materials such as bricks, stone, concrete blocks, mortar and grout. The active ingredients is a mixture of different-size particles – some larger, some smaller – to fill different-size voids. This ensures good penetration into porous substrates, resulting in good coverage and durable water repellency. Additionally, one active ingredient in IE-6683 Water Repellent can chemically react with the substrate, ensuring long-lasting performance.

Silicone Antifoams

Effective at low use levels, silicone antifoams are available for use in the different forms of construction material manufacturing. They can be found as antifoam compounds (fluid reacted with hydrophobic silica), emulsion or even as powdered additive.

For example, Dow Corning® 2210 Antifoam is a 10% active antifoam emulsion in water. It is a cost effective means to control foam and air incorporation into mortar or concrete modified with superplasticizer, which tend to increase air incorporation. It performs at low concentrations (1% of superplasticizer content) and performs well at extreme pH values.

Silicone Resins

Silicone resins can be tailor made to fit with different application (Figure 3). They can be used as such on construction material to impart hydrophobicity and provide good beading properties or be emulsified to be used in architectural coating.

Silicone resin emulsions are used in paint or render as a substitute for a portion of the acrylic binder, where, in addition to improved water repellency, good weatherability are retained.

For example, Dow Corning® IE 2404 Emulsion provides an industry-proven way to improve water resistance and increase moisture vapor permeability (breathability) of architectural paint and facade render formulations.

Paints made with silicone resin emulsion Dow Corning IE 2404 simultaneously prevent water from penetrating the coating by binding directly with inorganic materials in the paint – resulting in a hydrophobic action – while allowing water vapor and other gases to "escape" through the porous surface. This is especially useful on water-sensitive substrates such as masonry, plaster and insulation where moisture can damage the material or lead to microbial growth.

Conclusion

SBTs have advanced innovation in construction thanks to differentiated, customer-focused applications. Dow Corning is leading these efforts through both existing solutions and new research efforts.

While the traditional attributes provided by silicon-based technology, such as hydrophobic protection and foam control are critical to many construction-related formulations, the industry gains many other benefits from this chemistry. Formulators, leveraging Dow Corning's technology and customer support, are finding new ways to differentiate their products and enhance product features such as better weathering, water/oil/stain resistance, binding of filler materials, and thermal/ resistance.

SBTs offer the best of two worlds, providing many of the performance qualities needed in all construction applications while enabling new functionality and leveraging new advances in chemistry to advance the industry.

Jean-Paul Lecomte, PhD is Technical Service Leader for Building Material Protection at Dow Corning Europe S.A., Seneffe, Belgium.

Reference:

1. Witucki, Gerald L., AETS Industry Specialist, Dow Corning Corporation, "The Evolution of Silicon-based Technology in Coatings", 2003.

Contact details:

Dow Corning Representation Office
Meral Building
Office Numbers 61, 62 & 63
Building No.2572, Road No.2833, Block No.428
Seef District
Manama, Kingdom of Bahrain
T: +97317562686  
F: +97317582052
www.dowcorning.com/construction