By: Seth Gladden
In this article, we will be continuing our series on understanding flooring adhesive terminology. For Part II, we will be continuing the discussion on some of the most important, and often misunderstood terminology regarding adhesives in the flooring industry. In case you missed Part I, I would encourage you to check it out here: http://fsspring2021.cfimag.com/mobile/index.html#p=8
As a quick recap, Part I was focused on moisture-related terminology and covered RH, MVER, pH, waterproof bond, water-resistant bond, ASTM E1745, hydrostatic pressure, and moisture barrier vs moisture tolerant adhesives.
Since moisture is such a massive topic, it took all of Part I to cover. Part II will cover two categories, but will explore in much the same detail some of these important terms. Below you will see the following categories explained in depth: Substrate and Time.
Due to the amount of terminology present in the industry, this series will continue in the next edition as well, so stay tuned for Part III. However, let’s go ahead and jump into today’s categories.
SUBSTRATE… According to Merriam Webster Dictionary, a “substrate” is “the base on which an organism lives” or “a substance acted upon…”. However, with its Latin prefix sub- (below) substrate refers to a layer under something else. In flooring, that layer can be concrete, wood (plywood, OSB, etc.), existing flooring materials (well-bonded vinyl products, terrazzo tile, etc.) or other surfaces that adhesives are used to bond flooring material.
Used in this context, it might be better to refer to a substrate as a foundation, since what you put on top of an adhesive is only as good as the foundation (substrate) it is bonded to. This is why substrate preparation (proper or improper) has such a massive impact on the outcome of any flooring installation. This foundational step must be given the respect and care it deserves and makes understanding the terminology behind it that much more important. For more information on proper substrate preparation, check out TAYLOR TIME LIVE – S1 E2 – “Prep for Success”. Below are some of the most frequently referenced terms regarding substrates.
- Porous = In reference to flooring (usually concrete), porous means the substrate will absorb products (adhesives, coatings, etc.) into its surface pores (capillaries, etc.). This is a key factor for topical concrete moisture-blocking products and can also affect coverage rates and/or performance for many flooring adhesives. A simple, sixty-second waterdrop test (ASTM F3191) can be performed to check the porosity of concrete and can save you from spending extra time and money. Be cautious when dealing with porosity however as some products and manufacturers require different concrete surface profiles (see CSP below) to attain porosity.
- Non-Porous = When dealing with flooring, a non-porous substrate does not allow absorption of products/adhesives. Although many flooring adhesives and applications allow a non-porous substrate, always check the product documentation to ensure you are using the right trowel size to avoid unwanted telegraphing, product slippage, adhesive bleed-up through joints or other related issues. It is vital to note that most concrete coatings, especially moisture-barrier products, require a porous substrate (see above).
- Concrete Surface Profile (CSP) = A concrete surface profile (CSP), is a measurement of the surface roughness as defined by the International Concrete Repair Institute (ICRI) on a scale from 1-10 (1 being very smooth and 10 being very rough). This is determined by measuring the surface profile depth, or in other words, the distance from the top of the peaks to the bottom of the valleys in a concrete surface (when viewed as a cross-section). Often referred to as its texture, the CSP scale of 1-10 ranges from approximately 1/32” (CSP 1) to 1/4” (CSP 10) variance. Many manufacturers of topical moisture-barrier products require a certain CSP in order to achieve both a porous substrate as well as a mechanical bond.
- ASTM F710 = Considered the gold standard in flooring substrate preparation, this ASTM was created to outline the proper way to prepare a concrete substrate to receive resilient flooring. However, this ASTM is often used by flooring adhesive manufacturers as a reference guide for all kinds of flooring substrate preparation. Some of the biggest factors called out specifically for all kinds of flooring products are the following.
- Flat: ASTM F710 calls out that a substrate must be flat prior to an adhesive being applied and a floor covering material being installed. While this is an important part of substrate preparation, flat is often confused with level. These should not be confused as flooring adhesive manufacturers do not require a level substrate to achieve a proper bond. A flat substrate however is extremely important as it will help prevent unwanted telegraphing, hollow spots, or unsightly undulations in the finished floor.
- Free of contaminants: This is an extremely important part of ASTM F710, especially when it comes to flooring adhesives. Due to the chemistry of most adhesives, unknown contaminants can interact with them in ways that result in flooring failures. Contaminants can come in many forms and from many sources, so knowing the history of the concrete and ensuring you have a slab free of contaminants can save you a lot of time, money and callbacks.
- Structurally sound: This sounds easy, because let’s face it, concrete is one of the most common, and robust building materials on the planet. However, there are a lot of things that can happen to concrete that will adversely affect it. Most often, this will be more of a concern with older concrete and should be something that you pay special attention to when doing renovations or remodels, however even brand new concrete can suffer from not being structurally sound. Everything from stress fractures, cracking, crazing, spalling, pH loss, rebar corrosion, and excessive efflorescence can all signal that a concrete slab has begun to lose its structural integrity. Remember, thinking of a substrate as a foundation will help you understand the importance that this qualification plays in the success of a flooring installation.
TIME… You can’t make more of it, but you can use what you have wisely. When it comes to flooring adhesives, knowing the meaning behind the different times can help you correctly plan your jobsite and optimize it for both you and your client. It is important to note that not all flooring adhesive manufacturers use the same “time” terminology for the same things. Some terms are often used interchangeably, but they may carry different meanings, so always check the documentation, or contact that company technical support if clarification is needed.
- Open Time = Commonly used in reference to wet-set adhesives, this is the time from adhesive being spread until you can begin installing flooring material.
- Flash Time = Typically used in reference to dry-set adhesives, this is the time needed for an adhesive to dry-to-the-touch (no transfer to fingers) prior to flooring materials being installed.
- Working Time = The amount of time that flooring material can effectively be installed and still meet warranted performance levels. This starts after “open time” or “flash time” depending on the adhesive.
- Dry-Time = This is one that can be a source of confusion as some manufacturers use it to describe “flash time” and some use it to describe “cure time”. Technically, this term should refer to the amount of time it takes an adhesive to fully dry, meaning all the way through (not just the top layer), however this is sometimes hard to quantify given substrate and atmospheric conditions. This is why at TAYLOR, we do not reference “dry time” and instead rely on the other terms found here.
- Cure Time = This is the amount of time that it takes an adhesive to be fully cured and meet the intended performance characteristics. This does not mean that the adhesive is done fully crosslinking (see Part III, next edition) as this can take much longer (days or even weeks), however it does mean that the product will perform according to all the warranted levels.
- Pot Life = Commonly used in reference to 2-part epoxy systems, this is the amount of time a product has from when it is mixed until it sets up in the pail. Once the epoxy is out of the pail (on the substrate) it may remain viable a little longer than in the container. This is due to the heat generated by the exothermic chemical reaction when the components are combined, and when confined in the pail the heat has nowhere to escape.
As you can see, there is a lot of meaning behind each of these commonly used terms. In fact, there is far more that could be explored and understood in each of these categories, so I encourage you to continue doing your own research. Understanding exactly what you are working with will help you stay ahead of the competition, save you time and money, and achieve a better result.