Water Repellents: New Times Demand New Solutions

Why new generation water repellents deserve to be evaluated on their performance, not on their solids content and type.

Larry Schwietz, Founder, L&M Construction Chemicals

The story goes something like this. A newlywed couple was preparing dinner at their home. The wife was preparing a roast, just like her mother had taught her, adding spices and then cutting the generous piece of meat in half before placing it in a large pan and then into the oven. The young husband observed this ritual and inquired, "Honey, I was watching you prepare the roast today and am wondering, why did you cut it in half before putting it in the oven?" She replied, "I don't know why. That's just the way my mother taught me." Some days later the young wife relayed the incident to her mother and asked why she was taught to cut the roast in half, to which her mother replied, "I'm not sure, that's the way your grandmother always did it. She's in the living room, why don't you go and ask her?" So, into the living room the young bride went. After relaying her husband's question to her grandmother, the grandmother quickly responded to the young bride, "Oh, honey, that's because I never had a pan big enough to cook a whole one."

Kindly keep this story in mind as we proceed.

The way it was
Some 30 years have passed since medium weight silane water repellent treatments were introduced in the USA. At the time silane treatments were aggressively and successfully promoted to engineers, architects, government agencies and owners and were quickly accepted. The great success of this product was due to its deep penetration, excellent long-term water repellency and chloride-ion screening performance. Within a short period of time silane treatments quickly replaced the then popular penetrating epoxy sealers, particularly on parking garage floors and highway bridge decks in many states.

The downside
Offsetting their considerable benefits is the fact that medium weight silanes have a high volatility rate. The term "high volatility" means that silane radicals have a tendency to quickly evaporate from the surface before stabilizing, reacting and attaching themselves to the concrete substrate. This high volatility phenomenon occurs especially when unfavorable project environments exist, such as in hot, windy temperature conditions. To compensate for the medium weight silane's volatility, highly concentrated formulas containing 40% active silane solids were developed and promoted as the new formulation standard. High solids silane formulas increased the probability that a sufficient number of silane radicals would be available to effectively form a long term, hydrophobic, water resistant and chloride ion barrier in the concrete substrate, even during extreme application conditions. This product has stood the test of time and continues to provide good protection to the industry. But there are new solutions to this problem.

The first new wave of alternative water repellents
About the same time that silane treatments made their introduction, siloxane water repellent treatments were promoted in the USA as an alternative to silane. Siloxane formulas are chemically somewhat related to silane but have a higher molecular weight and a lower volatility rate. As a result, siloxane application treatments are more stable in hot, windy conditions. They also predictably develop positive protective results with less than half the concentration of active silane ingredients. Siloxane's larger molecular size, however, points to its weakness, as the depth of penetration of the treatment into the concrete is measurably less than that of silane treatments, and length of time of service in high traffic, high wear areas becomes questionable.

In the beginning most silane and siloxane treatments used high VOC content, organic solvent carriers, primarily methyl alcohol or mineral spirits. During the 1980's, market demand for lower VOC content, water-based products increased. In an attempt to reduce air pollution legislation was passed in various urban states, most notably, California and New Jersey, which restricted the content of evaporating organic solvents (VOC) in architectural products. In order to meet the product demand created by these low VOC requirements, water based emulsion chemistry for both silane and siloxanes grew slowly but steadily in the 80's and 90's, and companies such as L&M worked to develop new product technologies in order to provide new, effective, low VOC products.

VOC Compliance: What it meant and how the industry responded
In September 1999, sweeping EPA/VOC guidelines came into effect nationwide. These first-ever guidelines mandated reduced VOC content formulas for all water repellent products and 41 other architectural product categories sold in the US (See related VOC article in L&M Concrete News, September 2000). With these restrictions many solvent-based formulas were now out of compliance and had to be reformulated or removed from the market. L&M's popular PENTANE was one of the products that was affected.


  • Large siloxane molecules protect the substrate's surface, effectively fortifying this parimeter.
  • Smaller silane molecules penetrate deeply for long-term protection.
  • The proper combination of silane and siloxane molecules offer substantial effective protection.
All concrete, regardless of how "tight" the finish, has small, microscopic pores and fissures that allow water to penetrate and "wick" into the subsurface. This water, containing chloride, weakens and may eventually destroy the concrete itself when subjected to freeze-thaw cyles.
New formulas & superior performance
With our 30 plus years of working with water repellent formulas, L&M's chemists reviewed the relative benefits of silane and siloxane chemistry and developed a ground breaking, powerful, water-based emulsion that blends together and makes full use of the performance advantages of both silane and siloxane technology. That formula we call AQUAPEL. L&M's AQUAPEL utilizes low molecular weight silanes, an important constituent for achieving optimum penetration performance, and greatly enhances its performance with higher molecular weight siloxane components, which offer a great deal of protection at the substrate surface, effectively fortifying this perimeter. This is achieved without negatively affecting the water vapor transmission properties. And this performance is uniquely AQUAPEL's.

To enjoy the roast, you must kill a cow
A return to the introductory lesson regarding the roast is helpful at this time. The reason for cutting the roast in half no longer exists. New VOC regulations and new product advancements have rendered the sacred cow of "40% silane solids" to a historic concept. While silane products continue to perform well, the market availability of a new formula containing blends of silane and siloxane, along with the most recent advancements in emulsion chemistry, now means that there is a highly effective, cost competitive, alternative product which is neither solely high solids silane, nor does it need to be.

Our experience leads us to state our belief that performance standards are needed in the evaluation and selection of water repellent treatments. It has been the hallmark of water repellents, for as long as one can remember, that many project specifications simply reflect the finely nuanced testing results of certain proprietary products. It is not uncommon to see specifications with performance criteria that includes a litany of ASTM references with results reported to the second or third decimal point. This does not benefit the owner, as it too frequently uses inappropriate guidelines for product decisions.

We submit that when it comes to water repellent performance on exterior concrete the testing procedure and standard should be based on NCHRP 244 criteria. This comprehensive testing procedure provides a sufficient representation of the potential protective performance of water repellent products on horizontal concrete in the two most critical areas: water repellency and chloride ion reduction. Other criteria may be added, but these two types of protection are "meat and potatoes" primary.

Know for yourself
Please evaluate for yourself the physical performance of our AQUAPEL products and compare them directly with the published results of any high solids silane formula on the market. We believe you will be impressed with the results.

In closing, we encourage you to review this article with your local L&M representative. It is time to reevaluate the reasons we continue to do the things we do. In the case of water repellents, the days of cutting the roast in half are gone.

Results of testing done on AQUAPEL and AQUAPEL PLUS by CTL, Div. Portland Cement Assn. Skokie, IL


NCHRP 244, Series II

Avg. % reduction of moisture absorption after 21 days soaking:
Aquapel 84% Exceeds criteria
Aquapel Plus 85% Exceeds criteria

Avg. % reduction in chloride intrusion after exposure to 15% NaCl solution for 21 days:
Aquapel 84% Exceeds criteria
Aquapel Plus 90% Exceeds criteria

For more information about AQUAPEL and AQUAPEL PLUS, please contact your local L&M representative, or click here.


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© 2002 L&M Construction Chemicals, Inc. | ConcreteNews Spring 2002.

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