Specifying resinous flooring according to different chemistries

by arslan_ahmed | January 30, 2023 9:00 am

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By Joe Lasko

There are some flooring chemistries that have existed in North America for more than 15 years but are rarely specified relative to their epoxy counterparts. Epoxy has become the Kleenex or Band-Aid of resinous flooring. This being said, every construction project has certain needs that cannot always be solved by only specifying one flooring type or chemistry.

So, what other resinous flooring options are available? Urethane cements, methyl-methacrylate (MMA), urethanes, and polyaspartics have already been established as viable resinous flooring solutions for a variety of challenges. Urethane cements, for example, are good for resisting thermal shock from steam, grease, and other hot contaminants, while MMA can accept a fresh topcoat at any future time without requiring mechanical preparation.

The best practice for a specifier is to partner with a manufacturer. When partnering with a resinous flooring manufacturer, there are endless combinations of system builds that can be customized to achieve the perfect system for the customer. Epoxy still belongs in certain specifications, but urethane cements, MMAs, and polyaspartics all deserve consideration based on the project’s demands.

Therefore, it is important for one to understand not only the basics on what resinous flooring is, but also the different chemistries and why they each deserve consideration in specifications.

What is resinous flooring?

Resinous flooring, also known as fluid-applied or poured-in-place flooring, is common in industrial and commercial environments. Its properties allow for a smooth, non-porous, easily cleanable surface that cannot be achieved with any materials with grout or seams.

Resins can be a natural or synthetic liquid substance and sometimes have a yellowish or brown colour. Resinous flooring comprises specific resin formulas applied in several layers that bond together either adhesively or chemically. Once “cured,” the layers form a hard surface which has various performance properties such as ultraviolet (UV) stability, abrasion resistance, or chemical resistance, among others.

It is important to take all environmental factors and design choices into consideration before choosing a particular type of flooring as resinous flooring is not a one size fits all product. For example, some resinous flooring finishes are inherently slip resistant while others need to be customized by the end user for slip resistance. This can be adjusted by what product is broadcasted into the floor, the size of the broadcast, and the amount of it. The following are specific considerations which should always be included in a resinous flooring design and specification.

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Surface preparation

The most important foundation of a resinous flooring system is the substrate it is being placed on. The most common substrate is a concrete slab which is steel troweled or has a “darby” finish. The top or “cap” of the concrete substrate is the weakest part of the slab. Even if the resinous system can penetrate through the top of the slab, the “cap” still may delaminate from the rest of the slab, which would still result in failure.

To prevent this from being a weak foundation of the flooring system, a concrete surface profile (CSP) must be specified. CSP was created by the International Concrete Repair Institute (ICRI) to help standardize concrete repair methods. This specification is on a one to 10 scale, with the higher number being the most aggressive profile for products that will be laid thicker than 6.4 mm (0.25 in.). This is important to specify correctly, based on the system, because the CSP may show through a thin film system, or the substrate may need to be patched to prevent the CSP from telegraphing through. If a substrate is not prepared well enough, the product applied may delaminate and fail.

How the CSP is achieved is typically up to the installer, as they are liable for the installation of a resinous flooring. Depending on the specified profile, project size, and specified system, an installer can choose a range of mechanical surface preparation techniques. One thing that must hold true is that all the substrates must be mechanically prepared to the specified profile. Commonly used equipment include: grinders, shot blasters, scarifiers, scrabelers, hammers, and sometimes even needle guns. Always check with the manufacturer’s recommendations and best practice, as some do specify the type of mechanical prep equipment that must be used.

Moisture mitigation

Moisture in a concrete substrate is always present because concrete requires cement and water to cure. Moisture testing is always recommended. A common practice is to begin moisture testing after a concrete slab has been conditioned for 28 days after being placed.

In addition to having water as part of the curing process, a concrete slab on grade acts like a sponge and will absorb moisture from the soil or ground. The best way to avoid needing a moisture mitigation remediation is to specify a vapour barrier (i.e. vapour retarder) under the concrete slab. Whether its residual moisture from the curing process or moisture being introduced from a slab being on grade, when this moisture is left unchecked, it can force the resinous system off the substrate, causing a failure.

When writing a specification, it is important to include the manufacturer’s recommended maximum moisture for the flooring or coating system being specified. This way, testing can be performed and if the recommended moisture content is surpassed, a mitigation solution from the specified manufacturer can be used first. There are many types of moisture mitigation solutions that will vary from each manufacturer and by the chemistry being specified.

The two most common testing methods to test for moisture content are calcium chloride and relative humidity (RH) probe/metre. Calcium chloride results are reported in a unique unit,
kg/93 m²/24 hr (lbs/1000 sf/24 hr), while RH probe/metre provide a humidity reading as a percentage. Calcium chloride’s unit provides a correlation to the amount of moisture coming through the slab, and RH probe/metre gives a reading of moisture inside the slab at a 40 per cent depth. ASTM International standards for the two testing methods are ASTM F1869, Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride, and ASTM F2170, Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes.

Calcium chloride testing has been in use since the 1950s and has an advantage of providing a quantitative value to the amount of moisture that is actually reaching the slab. RH probe/metre in situ testing can provide more accurate data and a core with a probe in place, and can be evaluated more than once so that conditions that may be changing can be monitored. For more prestigious products, it may be best to use RH probe/metre.

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Cove base

One of the most popular reasons for specifying a resinous flooring system is because they are impermeable to water. A resinous system can act as both a user-friendly flooring system and as a waterproofing system. One of the most important aspects of creating a floor that has a “bathtub effect” is to specify a cove/wall base.

Ninety per cent of projects will only need a 102 or 152 mm (4 or 6 in.) cove base. Most projects will need 102 mm (4 in.), while commercial kitchens and other wet areas will require 152 mm (6 in.). Depending on the finish, and the chemistry of the system, one may be able to specify that a product goes even higher up the wall.

Transitions and terminations

One important detail often overlooked in a specification is knowing what terminations and transitions to call out. This can vary based on the type of flooring the resinous flooring is adjacent to. For example, if meeting up with a polished concrete finish, the resinous system will need to finish at “zero” or flush with the concrete substrate that is going to be polished.

The most important consideration regarding transitions and terminations is the resinous system should not be placed thinner at these locations. If the thickness is not correct, or matching the rest of the system, the terminations will be a weak point in the flooring system and will be the first points of failure either by delamination or chipping. After this has occurred, it can spread to the rest of the system leading to more delamination. The correct way to install these terminations is to “key” them in. “Keying” the substrate means to remove a certain amount of concrete to create a void that is the correct thickness to accept the resinous system as it is poured in place.

With best practices established that do not vary by chemistries, it is important to also look at the pros and cons of the most common resinous flooring chemistries.

 

1. Epoxy

Probably the most well-known chemistry in resinous flooring, epoxy is one specific class of polymers that contain epoxide groups, hence their name. There is an extremely large range of quality in epoxies, and most epoxy flooring and coatings typically fall in the middle of this range. While these are not the same high-end formulations the National Aeronautics and Space Administration (NASA) uses, the space agency sources the same base chemistry as flooring, paint, and adhesive manufacturers do.

The number of system designs using epoxy is endless and covers a wide spectrum of styles—from thin film all the way to trowelled down mortar systems. One advantage for using an epoxy system is its relatively reasonable material cost. Epoxy flooring systems usually have an attractive high-gloss finish and, depending on the formulation, can have zero volatile organic compounds (VOCs).

Not all epoxies are formulated or produced with the same quality. For example, there is a difference in residential-grade versus industrial-grade epoxy. Typically, they all have a long cure time (eight to 12 hours) which only amounts to 95 per cent cure. Reaching 100 per cent cure usually takes between seven and 10 days. Epoxy is also not UV stable, which means it will eventually yellow and colour shift when exposed to UV light. This is especially important when using these flooring systems in an area exposed to sunlight or fluorescent light for extended periods such as grow houses or exterior applications. In these cases, it is rare one will find a manufacturer that will recommend finishing with an epoxy topcoat versus applying a urethane or polyaspartic topcoat.

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Further, because of the wide variety of epoxy system designs and qualities available, it is important that a specification be very specific in the manufacturer’s system name or, at a minimum, the application method, finish selection for texture and colour, and a thickness be called out.

 

2. Methyl-methacrylate (MMA)

Next on the list is a lesser-known chemistry, MMA. This organic compound is most commonly used in acrylic plastics such as plexiglass or airplane windows. Pharmaceutical grade MMA is even used as a cement or glue in joint replacements.

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Known for its durability, MMA makes a great base chemistry for flooring and coating systems. The two largest pros for MMA are its ability to cure 100 per cent in one hour and down to -26 C (-15 F) or up to 38 C (100 F) as MMA is not temperature dependent. It is also known for being UV stable, which means it can be installed outdoors and will not yellow over time.

The two main cons of MMA are it has a relatively higher material price compared to epoxy. The second is it gives off an odour during installation. It has been described as a sharp, fruity aroma or one that is like a nail salon. Odours need to be managed and considered during any MMA project but is not usually a problem when proper ventilation methods are implemented.

Typically, the advantages of MMA chemistries listed above and its ability to accommodate recoating without mechanical preparation years later, can offset the higher costs of installation and managing the fast cure and stronger odours. One thing to keep in mind is no resinous system is odourless. Some systems just have less odour than others. MMA contractors are typically highly skilled installers and receive special training to be able to mitigate the odours with ventilation and to work with a shorter pot life that still allows for an excellent installation that can still cure in one hour.

 

3. Urethanes

Urethane coatings are typically applied as thin film coatings and as the final topcoat or seal coat to other flooring systems. Urethanes are most commonly created by reacting isocyanates with polyols. Other than floor coatings, urethane chemistry can be used in direct metal paint, truck bed, or tank linings, and generic waterproofing.

Urethanes for flooring topcoats are known for their high abrasion/chemical resistance and UV stability. Most urethanes see their best usage in large, high traffic areas or over top of an epoxy or hybrid system. The downside to urethanes is their sensitivity to moisture and temperature fluctuation. It must be installed within a certain temperature range. Also, similar to epoxies, urethanes have a longer curing time—varying between eight and 24 hours—which varies by manufacturer as well.

 

4. Polyaspartics

Polyaspartics, which are similar to polyurethanes, are relatively new to the coatings market compared to other systems with their updated chemistry. Other than flooring, they are also used in spray-applied wall coatings and tank linings.

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Manufacturers vary in opinion on typical uses for polyaspartics as a flooring material. They are typically substrate moisture sensitive, and most are used as broadcast coats or topcoats/finish coats in hybrid systems. Polyaspartics are great topcoats due to their fast cure times and the fact they are UV stable. They also cure very hard, which means they may not accept recoats later without aggressive mechanical preparation; this can vary slightly by manufacturer as well.

 

5. Urethane Cement

Urethane cement, also known as cementitious urethane, is exactly as it sounds—a urethane that is modified with cement. This chemistry has become a mainstay in resinous flooring due to its toughness. Two of its main strengths are its ability to withstand thermal shock of up to 115.5 C (240 F) at its maximum exposure temperature, and its moisture resistance, which can go up to 9 kg/93 m²/24 hr (20 lbs/1000 sf/24 hr) by calcium chloride testing or 99 per cent RH by RH in-situ probe testing.

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Some negatives to urethane cements are slower cure times—eight to 12 hours between coats— and the install temperature needs to be maintained between 15.5 to 26.6 C (60 to 80 F). Still, the pros of being extremely durable and tough can typically outweigh the cons depending on the project.

A word about topcoats

Different performance objectives can be achieved by choosing an appropriate topcoat, since this is what will be the flooring system’s first line of defence. It is becoming rare to find an epoxy product as a topcoat as the other chemistries perform better.

In hybrid flooring systems, often found in commercial kitchens, urethane cement is used as the body but different topcoats like MMA, polyaspartics, or urethanes still give the customer the performance or the look they are trying to achieve in their facility.

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After specifying

The specification has now been published, what else can be done to ensure the customer’s needs will be met and that one’s design is honoured as intended? Most projects will request that an onsite mockup is installed or that a step-by-step sample is produced of the specified system so that all parties involved can see the proper process of installing the system.

Making sure a qualified applicator is setup to install the specified system is a great first step. An installer should be able to provide references to previously installed projects which are similar in size or scope, as well as provide a letter or certificate indicating they have been trained and are authorized in the specified manufacturers’ system. These are two steps in submittals to help protect a project’s integrity and warranties.

[9]Author

Joe Lasko, MBA, XCLT, is the vice- president of Res-Tek Inc., a full line resinous flooring and coating manufacturer based in Cartersville, Georgia. He has more than 15 years of experience in designing, selling, and installing resinous flooring and coating systems. His responsibilities include designing flooring systems for market use, supporting the company’s sales team, and providing installation tech support to customers. He can be reached via email at joe.lasko@res-trek.net.

Source URL: https://www.constructioncanada.net/specifying-resinous-flooring/

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