The correct type of coating to choose for a concrete floor depends entirely on the intended use of the floor in various kinds of conditions.
Concrete needs protection regardless of where it’s located. The challenge is in choosing the correct type of protective material for differing conditions. The main purpose of a coating is to protect the slab from deterioration or contamination and to provide some added benefits such as aesthetics, improved wear, non-skid, chemical resistance, ease of maintenance, physical performance, to name a few among a myriad of other properties.
Floors are subjected to just about every kind of abuse – impact, abrasion, chemical attack and thermal shock. Concrete floors are not designed to take this continual abuse. Concrete floors are porous and tend to create dust from wear and abuse. They are also subject to abrasion and chemical attack. It’s for this reason that all concrete needs some sort of protection regardless of where it’s located.
The problem for most decision makers today, be they architects or facility managers, is to choose the most effective material and application that will result in the best performance and lowest life-cycle cost. It is increasingly clear that these individuals must rely on knowledgeable people to assist in proper selection, application and maintenance of the floor coating. The flooring specialist can guide the owner as to proper material, application and long-term performance, thereby reducing the long-term cost of floor maintenance.
A thorough selection process for a coating or topping system, including the writing of a detailed specification, and the preparation of detailed application procedures and final acceptance criteria, will give the owner the basis for choosing the right system. Here is a very comprehensive selection process which should be followed to narrow down the search for the right product and application for floor coatings.
Material Selection Process
1. Evaluate the surface
The flooring specialist must be able to provide a complete program from conception to long-term maintenance. The process should include the following:
• The first step in the selection process is to evaluate the existing surface to determine what is being worked with. The surface must be structurally sound, clean and not contaminated with any foreign material that could interfere with the bond of a new coating system. This includes concrete curing compounds.
• Is the surface distressed in any way? Does it have cracks, spalls or unevenness? Does the coating system require a level floor or one that slopes to a drain? Patching, repairing and levelling are as important as the coating system. It is important to note that any material used to level, patch or slope must be compatible with the total system. A cheap, low-performance patching/levelling material can ruin an otherwise good coating. It is also good practice to allow the same contractor that is doing the final work to make any necessary repairs.
• What type of surface preparation is needed for the area in question? Surface preparation is the most important step in the installation process and is critical to long-term performance of the total system. Unfortunately, there is no one “best way” to prepare the surface. The coating selection (thin film or thick) will have a bearing on the type of preparation. A thin-film coating will require preparation that will not leave a heavy profile. A heavy profile may require a levelling or fill coat before the thin film installation. This could double the estimated material cost.
2. Consider the Performance Conditions
There are four major areas of abuse that will dictate what a flooring system needs:
• Chemical exposure. Severity of exposure and types of chemicals are both very important. Materials differ widely in chemical resistance, making identifying the exposure, and the chemicals involved, very important.
• Abrasion. The amount of wear or traffic a surface will take is an important criterion. Any surface exposed to steel-wheeled traffic requires special treatment for long-term wear.
• Impact. Heavy loads and direct impact require a heavier build or thicker floor system.
• Thermal Shock. Temperature fluctuation or thermal shock is a condition that must be seriously considered. Thermal shock (which could occur during steam cleaning of the floor surface, for example) will cause a loss of bond through thermal expansion if the floor system is not chosen properly. The co-efficient of expansion of most coating systems is much higher than for concrete and must be carefully considered when selecting a material.
Once the degree of severity in the major areas of abuse has been identified, they must be ranked in order of importance for the particular project. This will provide a major focus for what is needed in terms of material and applied thickness. The last stage of the material selection process is possibly the most important. It involves how the coating is going to look aesthetically, how it’s to be applied, the time frame for installing the system, and lastly the project’s budget parameters.
3. Other considerations
Other considerations are often overlooked when selecting or specifying a floor coating system. These lesser considerations don’t necessarily contribute to the functioning of the system, but are important as they dictate the ability to install a particular system and assure owner satisfaction.
• Aesthetics. The final appearance of the floor surface is crucial. How an owner thought the floor was going to look versus the final appearance are sometimes widely divergent. Today, the same performance characteristics can be obtained with a variety of decorative appearances and surface textures.
• Installation parameters. In many cases, a flooring project has a very tight installation schedule. This limits many systems in the amount of time it takes to install a given material. In occupied areas, the odour of some solvent-based systems or the inherent odour of some materials themselves will limit their use. In selecting a material, the temperature of the surface at the time of installation is critical. Some systems are very temperature-sensitive and cure times can vary widely at lower temperatures.
• Life expectancy. Owners want a flooring system that is guaranteed to last for years. Maintenance procedures must be clearly outlined and understood for a realistic life expectancy.
• Economics. Economic value is the top requirement. At times, low-cost systems will prevail at the expense of more durable systems.
Review material properties and application procedures
The primary reason to go through a material selection process is to get the proper material for the application under consideration. It is critical to review technical data, performance characteristics and installation procedures. Technical data and performance review can be a challenge for engineers, owners and specifiers because there could be a lack of standardisation in the form of data presentation.
Specify type and thickness
At this point in the selection process, the type of material, application and thickness should be taking shape. Coatings for concrete can be classified by:
• Polymer type: epoxy, polyurethane, polyester, vinyl ester, acrylic, methyl, methacrylic, or others;
• Appearance: Is the floor required to be both functional and decorative?
• Finish: Is a smooth or textured finish preferred?
The selection process can narrow down the systems that will meet the thickness and the appearance requirements. Polymer type, however, becomes more difficult and assistance may be required to review data and compare performance.
There are thousands of formulations for various polymer coatings for concrete. Each one is different from the next. Epoxies and polyurethanes are the most commonly used polymers. In each type, performance and data vary significantly. Urethanes are used for thin-film to high-build coatings, have excellent abrasion and wear resistance, excellent gloss retention, and good to excellent stain and chemical resistance. Some urethanes have excellent elastomeric properties and, together with their low permeability, are used extensively in waterproofing applications. Most urethanes are solvent-containing coatings.
Epoxy formulations used in concrete floor coatings are typically 100% non-volatile (no solvent), have excellent adhesion, good to excellent chemical and abrasion resistance, and excellent mechanical properties. Applications include bonding adhesives, crack repair, concrete coatings, toppings and overlays.
Installation and inspection
Once the system has been chosen, the material must be applied and the job inspected and approved. The choice of a competent contractor to install the system is just as important as the appropriateness of the material used. A contractor trained to install a particular system (thin film versus thick overlay) is critical. Once the system and the contractor have been selected, co-ordination among parties must be maintained for best performance and user satisfaction. The job does not end with the application of the material. A long-term review, maintenance and repair program should be established for continued performance and satisfaction.
Floor surfaces suffer continual wear, abrasion and impact. Even the most durable surface will show areas of distress that require attention. A small amount of attention before installation will prolong the life of a flooring system. As years go by, the success of the project will depend upon the cooperation and coordination between the flooring specialist and the facilities manager. The result will be a trouble-free floor at lower cost.
Acknowledgements and thanks are given to www.concretenetwork.com and the article writer, Robert R. Cain, president of Key Resin Company, for the material contained in this article.