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Whether acrylic, epoxy, urethane or other technology, sealants applied to concrete pavers and other exterior surfaces have long fallen into a few distinct categories that describe their primary characteristics: Film-Forming or Non Film-Forming; Wet Look or Natural Look; Solvent Based or Water Based.
Not always have there been viable alternatives in some of the above categories; for instance, significant color enhancement in a water based sealant has been difficult to achieve. However, stiff competition amongst producers coupled with shifting governmental regulations has spurred a surge of technological advancements resulting in more options than ever. Along with options though come potential pitfalls, and understanding some important differences can make or break a job.
While there is a virtual cacophony of marketing claims to wade through, one easily identifiable truth is that when it comes to stain protection, with today?EUR??,,????'???s technology, a film-forming sealant is superior to a non film-forming alternative. Put another way, a physical barrier on top of the pavement offers ultimate stain protection. That however, is where the simplicity ends. Due to the flexible nature of an Interlocking Concrete Pavement, it?EUR??,,????'???s important that a film-forming sealant should likewise be able to move with the pavers without peeling or cracking. Further, because the joints allow penetration of water into the bedding layer, which introduces backside moisture, a film-forming sealant must be breathable at the microporous level in order to allow water vapor to escape while still protecting against stains. A film that can?EUR??,,????'???t breathe will trap that moisture and turn hazy or white, leaving customers displeased to say the least. In addition to pavers, many natural paving materials are subject to the same conditions depending on base and jointing materials.
Despite the excellent stain protection of film-forming sealants however, they?EUR??,,????'???re not completely without their drawbacks. Manufacturers frequently recommend a minimum waiting period of 60 days prior to applying a film-forming sealant in order to allow the vast majority of any potential efflorescence to bloom. This wait time can be hard to accept for both the production-minded contractor as well as an anxious end user. Rushing the process though may result in trapping efflorescence beneath the film, leading to another choice: live with the look or strip the seal, clean the pavers and then re-seal. Likewise, stains not removed prior to application of the seal can still be evident beneath the film, beyond the reach of cleaning products.
Additionally, some film-forming sealants can impact the slip and skid resistance of a pavement and may not be an ideal choice for a pool deck or a steep slope. Luckily, advances in non film-forming sealant technology have produced excellent alternatives that address some of the shortcomings of film-forming sealants while still providing very good stain resistance.
Because the protection comes from bonding to the minerals in the concrete or stone rather than a physical barrier on the surface, non film-forming products may be applied immediately after installation of the pavement assuming a clean and dry surface. Efflorescence is free to pass through where it can be removed with little to no degradation of the effectiveness of the seal. Further, because the surface characteristics remain unchanged with a non-film forming sealer, there is no impact on slip and skid resistance. Simplicity may be suffering, but the differences are important, and there are some outstanding products available depending on the demands of the project.
In addition to the protective benefits of sealants, the color of the sealed material can be enhanced or preserved, depending on the individual preference of the end user. Tumbled concrete pavers often see their otherwise vibrant colors muted in the tumbling process. While many end users may prefer the understated elegance of subtle colors, several more are surprised to realize how much more they love the look of their pavement during a rainstorm. Whether wet or natural is preferred, the look can be locked in with the application of the appropriate sealant, and both options are available in film-forming and non film-forming products.
Just as application practices and performance characteristics vary with film-forming and non film-forming sealants, so too do their finished aesthetic qualities. A film-forming sealant can either result in a satin or a gloss finish depending on the thickness of the film. As a rule of thumb, a thicker film yields a higher gloss.
A final and increasingly important differentiating characteristic of various sealers is whether they?EUR??,,????'???re solvent based or water based. Solvents have long been the preferred delivery vehicle for protective coatings due to their deep penetration, excellent ability to achieve saturation of the sealed material and their forgiving nature in the event repairs are required. As environmental concerns continue to mount however, governmental restrictions on solvents continue to tighten. New and stricter US EPA federal regulations for VOC (Volatile Organic Compounds) emissions are expected for 2008 that will render a number of current solvent based sealants non-compliant. Thorough discussion of VOCs is beyond the scope of this article, but suffice it to say that sealant manufacturers have been busy working on low VOC products to continue to meet the growing demand for hardscape surface protection.
While future innovations are sure to come, the current product offerings that meet the new VOC standards offer mixed results. Many manufacturers turned toward solvents that are exempt from the restrictions because they?EUR??,,????'???ve demonstrated low tendencies to create ozone or ?EUR??,,????'??smog?EUR??,,????'?? when evaporated into the atmosphere.
Unfortunately, these solvents also carry two critical drawbacks. First, their faster evaporation rates can compromise the quality and coverage rate of the sealer, particularly on hot days, giving rise to challenges for current application practices. Second, their much lower flash points create storage and handling safety concerns that distributors and contractors may find prohibitive.
Other manufacturers have pursued newer solvent technology that maintains high flash points and low evaporation rates while meeting the new VOC standards. This technology tends to cost a bit more, but the cost may be mitigated by more forgiving storage and handling requirements. Again, education is critical when making product selections.
Water based sealants on the other hand meet even the new VOC standards with ease. There are a few issues though that have prevented them from being an easy alternative to solvent based technologies. First, among the film-forming varieties their thicker films can result in temporary clouding under heavy moisture conditions, a troublesome aesthetic for many. Second, color enhancement has been difficult to achieve, though some very large strides have recently been made by some. Third, unlike solvent based products, application errors or unforeseen weather events are difficult to repair and tend to result in a costly and time consuming stripping process. Non film-forming products that offer very good stain protection are easy to work with but don?EUR??,,????'???t currently carry the vivid color enhancement desired by many.
Performance characteristics, aesthetic value, ease of use, longevity, governmental compliance, safety concerns and unit costs are the primary points of differentiation from one sealant to the next.
No single product is the best in each of the above categories, so it?EUR??,,????'???s crucial to whittle down the list of potential products and select the correct one. Understanding the intended use of the area, the aesthetic desire of the end user, the surrounding environmental factors and the characteristics of the material to be sealed all aid in paring the list of products down quickly.
Raleigh, North Carolina
Francisco Uviña, University of New Mexico
Hardscape Oasis in Litchfield Park
Ash Nochian, Ph.D. Landscape Architect
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