Silane Sealers for Concrete (A guide)

This article will discuss silane sealers for concrete as a protective agent to concrete structures and will cover topics such as the different classifications of concrete sealing agents. The blog post will then focus on silane as concrete surface sealant by discussing the pros and cons of using this chemical. Furthermore, the latter part of this post will differentiate the application of silane sealants on new and old concrete structures.

Silane Sealers for Concrete

Silane belongs to the group of penetrating sealing agents wherein a chemical reaction happens between silane and concrete components to create a protective barrier against moisture and soluble salt penetration. Compared to other penetrating sealers like siloxane, silane is more effective in terms of protective ability because of its small molecular size. Silane could enter the pores of the concrete matrix on a deeper level, thereby providing an extensive protective barrier.

What are sealing agents?

Sealing agents are chemicals designed to increase the durability of the concrete structures. These chemicals are applied on the surface of concrete to avoid any penetration for damage-causing substances such as water and soluble salts. Choosing the best sealing agent for your project may be one of tedious tasks you will encounter as there are numerous brands and product lines available on the market. Therefore, it is important to know and fully understand the characteristics that make a good sealant for concrete.

What makes a good sealing agent?

Protection

The primary characteristic that defines a good sealing agent is its ability to provide protection to concrete structures. While sealers are made to serve as a protective agent, it is important to note that they could not permanently stop deterioration but only delay or decrease its rate to an acceptable level to avoid regular maintenance costs in the long run. Specifically, good sealing agents are able to avoid water and soluble salt penetration as well as resist abrasive forces in order to extend the service life of the structure.

Safety

Furthermore, a good sealing agent should not result in an extremely smooth finish which could result in a slipping accident to users. This is of utmost importance when dealing with flooring projects, and generally good sealers are meant to promote safe environments even during its application. Some of the chemicals added to a sealer might be harmful when inhaled at great amounts, so it is prerequisite to look for volatile organic compounds present in the product and check if they are exempt or regulated by various regulatory bodies.

Appearance

Finally, the final appearance of the concrete surface is also a factor that could make a sealing agent remarkable. The aesthetic features that sealers offer range from sheen to glossy, although a few products simply do not make any significant visual enhancements to the surface. Yes, the final appearance has an impact on the structure, but it is important to note that the requirement of the project should be prioritized and followed. If it requires a glossy finish, then the best sealer product line to select should be one that provides that feature.

Types of Sealing Agents

The two classifications of concrete sealers are surface or topical sealers and penetrating sealers which significantly differ on their mode of surface protection.

Penetrating

From its name, penetrating sealers are those groups of sealing agents that are able to penetrate the pores of concrete matrix. These are commonly less viscous, colorless liquids that are resistant to UV radiation and abrasion forces. Silane and siloxane are the known penetrating concrete sealers in the market, although silane is found to penetrate the material deeper than siloxane. Generally, the depth of penetration depends on various properties of both concrete and sealing agent, but the molecular size of the sealer as well as the opening size of the concrete pores greatly affect the depth of penetration.

Penetrating sealers undergo a series of chemical reactions with the components of the concrete to form a hydrophobic film that acts as a protective barrier against water and soluble salt penetration.

Surface Sealers

Surface sealers, also known as topical sealers, protect concrete structures through mechanical adhesion on the surface. Some of the most common surface sealers in the market are acrylics, epoxies, polyurethanes, and some paints. It is important to note that topical sealers are not capable of bridging moving cracks but may enclose the non-moving ones. They are also used for aesthetic purposes as they are available at various ranges of finishes. However, this type of sealing agents is vulnerable to deterioration from UV radiation and abrasion resistance, so proper care and maintenance are required.

Silanes for Old and New Concrete

New Concrete

Because the reaction between concrete components and silane sealing agents are affected by pH (specifically favored basic conditions), the application of silane sealers on fresh alkaline concrete requires a shorter period of time to reach completion. Usually, silane curing requires a single day before the concrete surface can be coated with other chemicals or additives without any interaction with the initial silane spread. Although, it is best to follow the recommended drying time by the manufacturer.

Old Concrete

Old concretes generally have lower pH (or less basic condition) compared to new concretes because of weathering. As a consequence of its current state, some of the unwanted dirt and materials could interfere with silane, thereby reducing the amount of silane molecules that could react with the cementitious materials. Because of the synergistic effect of pH, purity of the substrate, and temperature (wherein reaction is favored at a hot environment), the completion rate of silane reaction is usually lower than new concretes. The estimated curing time for this type of substrate is up to approximately 3 days. However, again, the recommendation of the manufacturer should not be ignored.

Advantage and Disadvantages of Using Silane

As mentioned, silane is one of the most popular penetrating sealers for concrete in the market because it can offer higher depth of penetration compared to siloxane. Its effectiveness also increases when the solid content is high. Furthermore, penetrating sealers have low initial cost compared to other sealing agents. This goes with the amount of maintenance cost that silane incurs all throughout its service life. Lastly, the application of silane does not require any complicated methods and techniques. It can easily be sprayed and rolled on the surface, so the tools are readily available in the market.

On the other hand, the disadvantage of using silane as a sealing agent is its vulnerability to oil and grease staining. Penetrating sealers like silane are commonly colorless, so concrete surfaces still appear plain and visually less appealing.

Conclusion

This blog post discussed the topic “Silane Sealers for Concrete”. It was clearly explained that concretes require sealing agents to increase its durability by having protection against water and soluble salt penetration. Concrete structures like kitchen countertops are highly vulnerable to this kind of moisture attack, so their surfaces are normally coated with concrete sealants.

Furthermore, the two major classifications of sealants which are topical and penetrating sealing agents were differentiated in this article. It was emphasized that topical sealers adhere to the concrete surface by adhesion while penetrating sealers undergo a chemical reaction with the matrix components to create a specialized barrier against water penetration.

The advantages and disadvantages of using silane sealers were also discussed in this blog post. Some of the advantages mentioned are added protection from penetrating at a deeper level, being inexpensive, and easy application. On the other hand, the disadvantages of using silane are being prone to grease and oil staining and for some cases, regular reapplication on surfaces.

Finally, the main difference when applying silanes on new and old concrete is the required curing time, wherein new concretes require less than old concretes.

 For any questions and suggestions about this article, please feel free to submit your thoughts in the comment section below.

Frequently Asked Questions (FAQs): Silane Sealers for Concrete

What is the difference between silane and siloxane?

In terms of molecular size, silane is smaller than siloxane which gives it the advantage of penetrating the concrete matrix on a deeper level. This implies that the protection that silane gives against moisture penetration is much deeper compared to siloxane. However, silane has a pH requirement to catalyze its reaction unlike siloxane whose reaction is not dependent on pH.

How do you use siloxane silane sealer?

The use of this type of sealer does not differ from other sealing agents. One should make sure that the surface is clean and has no trace of existing sealing agents and coatings. It is recommended to clean the surface with appropriate cleaning solution which depends on the type of sealant previously applied on the structure. Let the surface dry, then apply the new sealing agent on the surface.

How long does sealer last on concrete?

The durability of sealing agents is different from one type to the other. Generally, acrylic sealants last shorter than epoxy or urethane sealing agents. Maintenance definitely plays an important role in prolonging sealants’ life, but acrylic sealing agents last to approximately 3 years while epoxies could reach a decade before it requires reapplication.

How long does siloxane sealer last?

The durability of siloxane sealing agents last depending on the quality of the product. Generally, it could efficiently repel water penetration from half a year to approximately a decade depending on various factors including regular maintenance and checkup.

Can moisture come up through concrete slab?

Yes, moisture and other fluids can penetrate concrete structures because they are innately porous and permeable. The movement of moisture goes both ways wherein the water that is already present in the structure could escape the matrix when the condition is favorable for vaporization. It is important to note that the porous property of concrete makes it vulnerable to corrosion attacks especially when the structure is reinforced with steel.

Do you need a moisture barrier under concrete?

It depends on the requirement and specification of your concrete project. If you are about to build a kitchen countertop, then the slab will be exposed to moisture on a regular basis, so it is advisable to apply sealing agents on its surface.

BIBLIOGRAPHY

Christodoulou, C., Goodier, C. I., Austin, S. A., Webb, J., and Glass, G. K. (2013). “Long-term performance of surface impregnation of reinforced concrete structures with silane.” Construction and Building Materials, Vol. 48, pp. 708–716, DOI: 10.1016/j.conbuildmat.2013. 07.038.

Hanjari, K. Z., Utgenannt, P., and Lundgren, K. (2011). “Experimental study of the material and bond properties of frost-damaged concrete.” Cement and Concrete Research, Vol. 41, No. 3, pp. 244–254, DOI: 10.1016/j.cemconres.2010.11.007.

Tittarelli, F. and Moriconi, G. (2010). “The effect of silane-based hydrophobic admixture on corrosion of galvanized reinforcing steel in concrete.” Corrosion Science, Vol. 52, No. 9, pp. 2958–2963, DOI: 10.1016/j.corsci.2010.05.008.

Xiong, G., Luo, B., Wu, X., Li, G., and Chen, L. (2006). “Influence of silane coupling agent on quality of interfacial transition zone between concrete substrate and repair materials.” Cement and Concrete Composites, Vol. 28, No. 1, pp. 97–101, DOI: 10.1016/j.cemconcomp. 2005.09.004.

 Ma, Z., Zhu, F. & Zhao, T. Effects of surface modification of silane coupling agent on the properties of concrete with freeze-thaw damage. KSCE J Civ Eng 22, 657–669 (2018). https://doi.org/10.1007/s12205-017-1718-z

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