Building owners and designers now insist that all facets of construction—including waterproofing—be as eco-friendly as possible.  Fortunately, manufacturers have developed products to meet this demand.  One type of waterproofing has proven particularly suitable for green building—crystalline waterproofing technology.

Produced by a few different manufacturers, these products can be applied as a slurry coat,  integral admixture or dry-shake powder for new slab construction. It has been used in many of the most prominent green-build projects in North America, including several that have been certified LEED-Platinum, the highest honor awarded by the U.S. Green Building Council.

How it Works

The chemical composition of each brand of crystalline waterproofing is different, but the basic technology is the same.  In the presence of water, the products react with calcium hydroxide and other byproducts of cement hydration to create a microscopic non-soluble crystalline formation that fills the pores and micro-cracks in concrete.  As long as moisture remains present, the crystals continue to grow, potentially reaching lengths of many inches.

The same chemical reaction will occur even if the exposure to water occurs years after the crystalline waterproofing was installed. The ability to reactivate in the presence of water gives crystalline-treated concrete the ability to “self-seal.” When cracks form due to curing shrinkage, settling, seismic activity, etc., water entering through them causes new crystals to form and grow, blocking and filling the cracks.  This reaction will occur for the entire life of the concrete structure, automatically sealing cracks up to half a millimeter (1/64 inch) wide.  Obviously, this can help to dramatically reduce the long-term maintenance and repair costs.

Although crystalline waterproofing  can be applied in several different ways, adding it to the mix at the batch plant has gained popularity in recent years. (Other methods include shaking a dry powder onto green concrete and brushing or spraying it on as a slurry coat for existing concrete structures).  Slurries and dry-shake applications  penetrate from the surface only, but admixtures have the benefit of ensuring that the crystalline formation occurs uniformly throughout the concrete.  Most admixtures are powdered, although Aquafin markets a liquid admixture which claims to eliminate the risk of clumping and enhances distribution.  It should be noted that Xypex crystalline admixture is marketed in soluble bags that have over ten years of field use with negligible reports of clumping or dispersion issues.

Advantages

Crystalline waterproofing has several unique green construction benefits.

From an application standpoint, it requires far fewer protections for the waterproofing crew.  There are no Volatile Organic Compounds (VOCs). Respirators and disposable coveralls are unnecessary.  Air quality is unaffected.  With the admixture products, the waterproofing is installed at the same time as the concrete, so it eliminates all the extra labor and material resources needed to install traditional membranes and coatings.  Frequently, these products can reduce the amount of onsite equipment, and significantly decrease the amount of excavation and backfill required, as crystalline-enhanced concrete can be applied blindside, instead of needing the larger construction footprint that membrane installation typically calls for.  So there’s less material, less waste, and less digging.

Crystalline requires no solvents, and there are no petroleum-based products to leach into the environment. The technology is so safe that many crystalline products have been certified as safe for use with potable water tanks.

Finally, the waterproofing is permanent, and hairline fractures will self-seal for the life of the structure. Finally, at the end of the building’s life span, the concrete can easily be recycled into aggregate or fill, with no membranes or coatings to remove.

Contributions to LEED

Currently, the most popular green building rating system is administered by the U.S. Green Building Council (USGBC).  Their Leadership in Energy and Environmental Design  (LEED) program has certified more than a billion square feet of new construction since being launched.  Periodically updated since its inception in 2000, the cur-
rent iteration—LEEDv4—awards points across a handful of categories, such as water and energy conservation, waste reduction, and habitat conservation.  Upon completion, the point tallies are verified and the project is certified.  Those that go beyond the minimum point requirements can be certified at silver, gold or platinum levels.

Kryton, Xypex, Aquafin and others which market an entire line of various crystalline waterproofing products can contribute to the following LEED credits:

Sustainable Sites: Crystalline waterproofing admixture can contribute up to two points under Credit 5.1 Site Development: Protect or Restore Habitat by reducing the size of excavation is required.  Because the product is added directly to the concrete mix, there’s no need to excavate an area for workers applying physical membranes.

Materials & Resources: Crystalline coatings can contribute an additional point under Credit 2.1: Construction Waste Management due to its recyclability.  Spray-applied coatings and self-adhered membranes are difficult to remove, so this concrete usually goes straight to the landfill.  Crystalline-treated concrete, though, is easily recycled post-demolition, eliminating waste.  As noted above, some of these admixtures are available in mixer-ready, pulpable bags, which eliminates packaging waste around the jobsite.

Environmental Quality: Indoor air quality is a significant factor under current LEED guidelines.  Because crystalline waterproofing involves no volatile organic compounds, and does not affect air quality, it can contribute up to one point under Credit 4.2 Low-Emitting Materials: Paints & Coatings.

Innovative Design: LEED rewards points for the longevity and durability of the structure.  Up to one point can be awarded in this category because crystalline products stop corrosion, increase freeze/thaw durability, and protect against chemical attack, carbonation and other detrimental effects.

Conclusion

“Crystalline waterproofing products provide many key advantages to concrete structures and contribute toward LEED certification,” says Chris Chen, director at The Penetron Group. “In their report on Chemical Admixtures for Concrete, the ACI states that crystalline admixtures—as true Permeability-Reducing Admixtures for Hydrostatic conditions (PRAHs)—are sufficiently stable to resist water under pressure and can eliminate traditional petrochemical-based membranes.”

He points out that in addition to LEED benefits listed above, they enable shortened construction schedules, do not require additional energy input (heat or electricity) and do not create environmentally unfriendly waste at the end of a building’s useful life, making this type of product very attractive.

Crystalline waterproofing sys-tems are gaining acceptance as the preferred treatment method for eco-friendly construction.   They provide a solution that’s not only sustainable and environmentally-sensitive, but also effective, easy to use, and extremely cost-effective.