Selecting Polymers Flooring Systems
Each different resinous flooring system placed on a concrete slab is formulated to withstand a specific type of environment. In addition, the levels of support and service from manufacturer along with, technical competence, of the installing contractor may vary significantly. Taking time to evaluate and analyze these factors, along with a determination of the anticipated operating conditions versus available material options, ensures longer floor life, lower maintenance costs, and better performance.
Know the Substrate
New and existing concrete must be properly evaluated before installing a coating or overlay system. Concrete is a versatile and strong building material, but it has a host of potential problems. Cracking, crazing and map cracking, low resistance to wear, dusting, scaling, popouts, blisters, spalling, moisture vapor transmission, ponding and inadequate slope to drain, curling and warping, efflorescence, and freeze/thaw cycles are all indications of concrete problems and detrimental to the integrity of concrete.
A basic understanding of concrete's design, placement, curing, and finishing techniques is necessary. This allows the proactive owner/engineer to positively impact the concrete specification and installation on new construction which ultimately impacts the strength and permeability of their concrete. This paper will focus on the basic information necessary to help insure that the resinous floor and wall systems which best meet your needs are selected. In order to do this, a basic guide for concrete design is discussed, followed by criteria for protective system selection. Finally, an overview of available resin technologies and their relative strengths and weakness is discussed.
Concrete, Stronger than ever?
With all of the rapid advances today in science and technology, it is alarming to note that some experts believe that the quality i.e., durability of concrete, has been going the wrong direction in the last 20 years. Shilstone and Shilstone, Authors of many articles and lectures at ACI (American Concrete Institute), believe the reasons for this are as follows:
The key to a successful finish floor acceptance of a non-permeable flooring system is to provide minimum disruption to the even distribution of paste and aggregate. Compaction is important but it should be kept to a minimum to prevent bringing too much paste to the surface. Too severe a finish of any kind will bring water and paste to the surface. This will be the weakest, most porous and crack-ridden portion of the concrete. These reasons have everything to do with a high water / cement ratio, and high paste concentration.
Concrete Specification Review
Concrete specification should include the following to maximize the probability of successful bonding of non-permeable floor coverings:
The preferred placement which should always be specified in compaction and a light steel trowel finish to minimize the disruption of the paste and aggregate distribution. The best finish is a light steel trowel finish, as this will provide for the least amount of paste brought to the surface. Any other type of finish will require more significant surface preparation.Remember that the paste on the surface has the highest water / cement ratio and, therefore, will be the weakest part of the concrete.
Cure conditions should be clearly stated in any specification for concrete to accept non-permeable durable goods. The best results will be with a minimum 7 day wet cure provided by ponding, sprinkling or wet coverings. All curing compounds should be avoided. Under no conditions should the concrete be placed when temperatures are below 50°F (10°C) or above 90°F (32°C). Prior to application of any resinous coatings or toppings, calcium chloride tests should be performed to evaluate the rate of moisture vapor transmission of the slab. The resinous system manufacturer should be consulted concerning allowable moisture levels prior to product application.
The Selection Process
Figure 5.7, lists the concerns and needs of plant engineers planning a floor renovation, based on a national poll. Additional reasons for flooring projects include: aesthetics, light reflectivity, impact, material, maintenance procedures and potential for future change in area usages.
HEAVY FORK LIFT TRAFFIC - The specified system must withstand high abrasion from rolling loads. Generally, thicker systems (1/8") or greater are used to provide sufficient wear resistance and protect against impact when forks or the forklift load is dropped.
CLEANABILITY - Maintenance of clean surfaces is critical in certain areas. A delicate balance must be struck between cleanability and slip protection, especially in wet areas. In addition, selected systems should resist both the mechanical and chemical demands of the cleaning operation. Working closely with the specifier, manufacturer and installing contractor will help insure cleanable systems are installed. It is a good idea to have a sign off on submitted samples to create a standard of performance or, better yet, sign off on (or approve) a project mock up prior to installation of the entire area.
SLIP RESISTANCE - As detailed above, needs for cleanability and safety dictate required surface profile. Typically, for more aggressive requirements, aggregates are incorporated into the resinous floor system. The size, shape, and type of slip-resistant additive is determined by the environment the floor is exposed to. The degree to which these aggregates are covered or encapsulated impacts how aggressively they protect against slips and falls. Often overlooked, Slip resistance is an important system attribute to help insure worker safety. Accidents attributed to slips and falls cost employers millions annually in lost time and lawsuits.
HARSH CHEMICALS - Both process and cleaning chemicals present challenges to resinous protection systems. Temperature, length of exposure (time), concentration, maintenance routine, and potential for chemicals to mix with other chemicals are all necessary pieces of information. With this information, the material manufacturer can recommend the proper protective system.
HEAVY FOOT TRAFFIC - Foot traffic can be aggressive from an abrasion standpoint if abrasive dirt is present in an area. Thin mil coating systems (< 10 mils) may not provide sufficient long-term protection. Ability to recoat these areas must be considered. If the area has extremely limited access, a high build (15 mils or greater) should be used.
VIBRATION FROM MACHINERY - This condition may lead to cracking or delamination of resinous floors. If isolation pads are not possible, flexible systems can be utilized. Today, non-externally flexibilized epoxy systems represent the state-of-the-art to address these situations.
HEAVY STEEL WHEEL TRAFFIC - Steel filled epoxy systems will withstand this condition quite well. Available in 1/4" thick systems, they also withstand point loading and heavy impact.
SECONDARY CONFINEMENT - Collection of chemicals to segregation and re-use or treatment requires protection of the substrate. Typically the resinous protection system must withstand a minimum 72 hour exposure to the chemical in question. The same information required for 'harsh chemicals' above must be gathered for a manufacturer to make a specific recommendation.
USDA / FDA - Federal regulations require that resinous system manufacturers exclude certain chemicals from their product formulations. A phone call to the resinous system supplier is typically all that is necessary to ascertain their compliance with these regulations.
CONDUCTIVITY/STATIC CONTROL - These systems are used where a potential explosion or fire hazard exists (in the case of conductive systems) or, the potential for damage to sensitive electronic equipment or components is present (static control).
THERMAL SHOCK - When a spill of hot material occurs on a resinous floor or wall system, the system must be capable of withstanding the heat exposure without complete degeneration of its physical properties. Also, different liquids dissipate their heat at different rates (for example grease versus water). Most epoxies will withstand intermittent temperature exposures of 120°F. Hybrid systems are available for exposures up to 500°F.
AESTHETICS - This attribute should not be overlooked. What the resinous system looks like upon completion, and its appearance 6 months, one year and 5 years from now, given current and anticipated operating conditions and maintenance may be important. Because certain resinous systems are many times more abrasion resistant than concrete, it is possible to select systems that retain their aesthetics even in the face of tough operating conditions. The impact of clean facilities on employee morale and potential customers is obvious.
LIGHT REFLECTIVITY - Often areas with high lighting or poorly lit areas can be significantly brightened through the use of light colored resinous protection systems. Initial gloss levels can be specified for resinous systems. Also, gloss and color retention information can be secured from the manufacturer.
IMPACT - Resistance to impact protects the substrate from damage from dropping or falling objects. Generally, troweled 1/4" toppings have been used for these applications and have performed fairly well. A new technology, based on a flexible epoxy binder resin has displayed superior performance.
MICROBIAL CONTROL - Epoxy systems are available with integral biostats. It is important to verify that the manufacturer's claim for both the biostat and finished epoxy system are substantiated.
Finishes selection is a process, that when followed, can provide satisfactory and lasting results. The steps are as follows:
Plant Engineer's Reasons for Floor Renovation
System performance (relative to the environment in which it is installed) depends greatly on the chemistry and flooring type selected for the application. Although there are a myriad of technologies used in the industrial flooring industry, the most traditional and widely available include acrylic, epoxy, polyurethane, polyester, or vinyl ester.
ACRYLIC RESINS - vary from extremely hard, brittle solids to elastomeric (rubber-like) structures to viscous liquids. These materials tend to have excellent water and weather resistance. In addition, they are stable under moderate thermal shock conditions, but provide lesser mechanical strength, chemical resistance, and adhesion compared to alternate systems.
EPOXY RESINS - are thermosetting products known for toughness, chemical resistance, and sub-surface adhesion. There are several different types including:
BISPHENOL A - is a cost-effective, general-purpose resin which demonstrates excellent alkali resistance, good acid resistance and fair-to-good solvent resistance.
BISPHENOL F - is a low-viscosity material which provides excellent alkali resistance and offers improved acid and solvent resistance compared to Bisphenol A.
EPOXY NOVOLAC - is fast curing and offers excellent protection for secondary containment where resistance to strong alkalis, acids, and solvents are required.
POLYURETHANE RESINS - are thermosetting or thermoplastic and demonstrate moderate chemical resistance and good resistance to diluted acids and alkali. Polyurethane resins generally offer moderate adhesion, but good resistance to shrinkage. Aromatic-based systems offer fair UV resistance, while aliphatic-based types deliver excellent UV resistance.
POLYESTERS - are fast setting, high strength, and demonstrate good resistance to acids and most solvents, but they are generally susceptible to alkali attack. Polyester resins experience a relatively high amount of shrinkage. Styrene flammability and fumes must be considered when using this product.
VINYL ESTERS - provide ultimate performance in chemical / corrosion resistance. The products are typically formulated in high build, fast curing systems for corrosion resistance and toughness. Again, styrene flammability and fumes must be considered.
Ideally, all monolithic, non-breathing floors should be installed under the temperature and humidity conditions expected during use. If installed at low temperatures and / or high humidity, raising the temperature and / or lowing the humidity above the concrete after installation leads to disbondment, because water vapor moves to the higher temperature and lower humidity. If humidity and temperature during installation significantly differ from normal service conditions, water vapor is likely to create problems in disbondment, especially is changes are rapid.
Figure 6. shows the basic characteristics of each family of products.
There are overlaps in system applications; however, select types of chemistries are generally used for specific environments. Whether the decision is dependent on exposure to harmful liquids or excessive abrasion due to wear, the ultimate abuse the surface will experience must be understood to ensure a successful installation.
The selection process begins after a thorough new assessment is done and a full evaluation checklist is created of the potential abusive agents (extreme chemical exposure, light-to-heavy duty wear from rubber and / or steel wheel traffic, floors exposed to degradants such as thermal shock, etc.). There are several types of polymeric industrial flooring systems available to match the job.
COATINGS - are an economical, thin-mil system providing chemical resistance, ease of cleaning, and a non-dusting surface. Applications include areas exposed to chemical splash or spill and light-to-moderate traffic. Because coatings are typically 40 mils or less, they will not hide or mask surface imperfections. They will not provide slope or pitch to drain, rather they follow the contour of the substrate. Coatings withstand only light thermal shock and impact conditions. Many base chemistries are available to choose from to meet specific chemical resistance.
BROADCASTS - are an economical flooring system using fine aggregate granules combined in a resin matrix. Broadcasts provide good skid inhibition and chemical resistance. Applications include areas experiencing light-to-moderate chemical, impact, and traffic exposure. Full 1/8" to 3/16" broadcast systems can be used in many of the applications where 1/4" mortar systems were previously specified. Over 15 years of performance have demonstrated these systems can withstand moderate impact and abrasion conditions. For heavy impact, thermal shock and abrasion conditions, consult the manufacturer for specific recommendations. As is the case with coatings, many base chemistries are available to choose from to meet specific chemical resistance. Slurry Broadcast systems will mask minor surface imperfections.
THICK-MIL TROWELED - systems employ a mortar material with aggregate fillers in a resin matrix for maximum strength and protection. This approach provides high impact resistance, level surface, easy maintenance, good skid inhibition, and resistance to thermal shock, or chemicals. Mortar systems are often used to re-pitch floors to provide slope to drain.
THIN OR THICK-MIL BROADCAST/TROWELED - is a mortar-like system with highly decorative aggregates combined in a resin matrix. Applications include areas needing highly decorative surfaces and resistance to wear and chemical attack.
MICROBIAL INHIBITING - is a thin or thick-mil system with integral microbial control agents that prevent the growth of gram-positive or gram-negative bacteria, fungi, viruses, and yeasts. Applications include areas where inhibiting microbial growth, safety, odor abatement, cleanliness, and hygienically superior environments are required.
With hundreds, if not thousands of resinous floor and wall protection systems available today, the selection of the proper system to meet necessary functional and aesthetics demands is a challenge. To insure system performance, a basic knowledge of concrete (the substrate over which 80% of all high-performance resinous systems are applied) is necessary. Once a proper substrate has been placed, or remedial action has been taken on an existing slab, key operational environmental conditions under which the product must perform are evaluated. This information, coupled with desired product attributes, form the basis for a rating system which weighs the importance of key performance factors.
Finally, available chemistries and basic types of systems are evaluated and compared with actual product needs. At this point, or if you need assistance at an earlier stage in this process, it is strongly suggested that you consult a manufacturer familiar with the particular type of application you are doing. Don't just take their word for it, use due diligence and check their references as well as those of their installing contractors.
A qualified manufacturer can provide local representation, budget figures, on site technical assistance and a network of company-trained, approved applicators. Specifications can also be provided.
Because of the need for minimal disruption or continuous operation present in most pharmaceutical environments, repair of or shut down due to resinous system failure can be extremely costly. Acquisition and use of certain information coupled with consultation and servicing by a qualified manufacturer will help insure project success.