High-performance brick floor in a bakery installed with corrosion-resistant mortar and setting bed
Selecting the right flooring
01 January 2000
With the growing sophistication of industrial processes, the flooring of an industrial facility is subjected to intensely corrosive chemicals. JOHN H KEISER JR, vice president of Atlas Minerals and Chemicals, provides guidelines on how to select the right industrial flooring system for any particular application.
IN the past, industrial flooring systems consisted of earth, concrete, wood and asphalt. For example, the iron and steel industry was served well by earthen floors which resisted the impact, temperature, and live and dead loads to which they were subjected. Similarly, in the early years of the textile industry, wooden floors were used above grade and concrete floors on grade. Asphalts were used for the protection of concrete floors subject to acids.
As industry became more sophisticated, chemicals became more prevalent in various production processes. Plant engineering and maintenance personnel were required to find more substantial protection for concrete floors to combat the chemical, physical and thermal problems inherent with modern flooring. Coupled with the requirements of various governmental agencies, industry responded by making available a multitude of products that solve a range of flooring problems.
These systems include coatings and sealers, polymer flooring (monolithic toppings), polymer concretes, and brick and tile floors which are bedded and jointed with various mortars and grouts. Before reviewing these various flooring systems in detail however, substrate and surface preparation, two major factors which are key to the success of any flooring system should be addressed.
Substrate engineering
For excessively wet process areas, floors should be sloped to drains and trenches at a minimum of 3/16 in (5 mm) per foot, or preferably 1/4 in (6 mm) per foot. Process areas subject to heavy chemical spillage will last longer, with minimum maintenance, if the chemicals flow to drains, instead of standing, puddling, and becoming concentrated due to evaporation.
Periodic washdown of properly sloped floors also contributes to higher standards of sanitation in the food and beverage industry. For process areas subject to light to moderate spillage of process chemicals and aqueous wastes, floors should be pitched to drains and trenches at a minimum 1/8 in (3 mm) per foot.
All concrete should be free of ridges and depressions to assure a true and flat plane of the applied flooring. Maximum variation under a 10 ft (3 m) straight edge laid in any direction should be 1/8 in (3 mm). This is particularly true of thin cross-section polymer flooring systems.
Surface preparation
New concrete should be cured for a minimum of 28 days. If concrete appurtenances are required, no release agents should be used on the concrete forms. No film-forming curing membranes should be used that could interfere with the bonding of the flooring system.
Existing concrete must be completely degreased and cleaned, and all chemicals must be neutralised before mechanically cleaning. For new and existing concrete, grit blasting or blasting is the preferred method of surface preparation because it maximises profile, thus optimising the bond of the flooring system. All defects in the concrete should be repaired before applying any flooring system.
Coatings & sealers
Coatings and sealers are applied from 1 to 10 mils (0.03 to 0.3 mm) per coat. They are used to:
Coatings and sealers are not to be construed to be physically rugged, heavy-duty, chemical-resistant barriers for protecting concrete floors.
The two most popular resin systems used to formulate coatings and sealers are epoxies and urethanes. Epoxy is a two-component, 60 per cent to 100 per cent solids system, utilising various hardening systems, that is, aromatic, aliphatic, cycloaliphatic, and polyamide. Urethane is a two-component, 40 per cent to 65 per cent solids, aromatic and aliphatic polymers system. Coatings and sealers are available in many colours, finishes and textures.
Polymer floors & polymer concretes
Polymer floors are usually installed at thicknesses of 1/4 in (6 mm) or less. They are distinguished from polymer concretes which are generally applied at thicknesses of 1/2 in (13 mm) or greater. Aggregate size could determine the difference between the two groups of materials.
This category of flooring materials is characterised by resistance to hostile environments and the capacity to withstand varying physical conditions. They are generally three-component, 100 per cent solids materials. The resin systems include epoxies, furan, polyester, urethane and vinyl ester. Furans are usually not used in polymer floors due to their propensity to shrink and their inherent black colour. Likewise, urethanes are not used in polymer concretes due to insufficient advantages over currently available resin systems.
Polymer floors have unlimited applications in the chemical, steel- and metalworking, food and beverage, pharmaceutical, electronic, and aerospace industries. These materials can be applied by trowel, screed, or spray. In addition, unique self-levelling and broadcast formulations permit speed of application and allow installation by persons with minimal experience. The systems can be installed with fibreglass reinforcement if required, and are available in various colours and finished surface textures.
Polymer floors are used to meet a number of construction challenges. For example, they are recommended when chemical resistance is required with minimum change in elevation. They are also used when:
And if imminent process obsolescence precludes more expensive flooring, a polymer system is a practical alternate. Other situations that make polymer systems an ideal flooring solution are when minimum downtime for a new installation is essential and when economical no-skid surfaces are needed.
Trowel and screed applications of polymer floors are much the same as those used for placing Portland cement and other cementitious materials. Spray-applied materials are similar to applying highly thixotropic coatings. As the method implies, self-levelling is the pouring of the material and permitting it to level. Broadcast systems are multiple coat applications of resin into which aggregates are broadcast to excess. The system is repeated until the desired thickness is achieved.
Epoxy carbon-filled formulations are available for applications requiring resistance to hydrofluoric acid, fluoride salts and strong alkalis. Conductive flooring can also utilise carbon fillers.
Polymer concretes are similar to polymer flooring in their chemical resistance and physical properties, however they have additional advantages. For example, they exhibit high early development of physical properties - to 5,000 psi compressive strength in two hours. They also display high ultimate physical properties - 14,000 psi compressive strength in 24 hours. Their low-viscosity resin systems permit ease of mixing and placing, and they can be poured in place and precast. Polymer concretes also provide excellent bonds to new and existing concrete.
Polymer concretes have found widespread use in various industries as flooring materials, precast trenches, trench covers, drains, sumps and manholes. Precast and poured-in-place equipment pads have utilised polymer concretes because of their outstanding chemical resistance and physical properties.
Brick & tile floors
Brick and tile are bedded and jointed with various mortars and grouts from thicknesses of 3/8'' (7 mm) to 4-1/2 in (114 mm) for individual units. These flooring systems are designed to provide the broadest range of protection against chemicals, steam and hot water, and physical impositions from heavy forklifts to highway vehicles. They are the easiest to clean and sanitise and have no equal when it comes to protection against the most hostile of environments, including chemicals, temperature extremes, and physical abuse.
Brick and tile are made from red shale and fire clay. They are essentially equal with regard to chemical, thermal and physical properties, the major differences being aesthetics - red versus buff colour. Carbon brick is used where resistance to hydrofluoric acid, fluoride salts and high concentrations of alkalis is required.
The success of any brick or tile floor depends on the selection of the proper material for bedding and jointing the brick or tile and the method of installation. The most popular mortars and grouts for installing brick and tile are furans and epoxies. Polyester, vinyl ester, phenolics and silicates are used for specific chemical resistance. Before a mortar or grout is selected, it is necessary to identify all chemicals present and the concentration to which the floor will be subjected.
In general, there are three types of chemical-resistant, sanitary floors. The first type is the heavy-duty industrial brick floor that can be installed on an impervious membrane (chemical-resistant brick and tile are not impervious). These floors are used to protect concrete against frequent spills of aggressive chemicals as well as physical abuse. For example, these brick floors are used in steel mills in areas adjacent to pickling, plating, and galvanising tanks; in power plants in deionising and demineralising water areas; in forming rooms in lead battery operations; and in chemical process plants.
The second type is medium to heavy-duty brick and tile floors that can be bonded directly to the concrete substrate. These floors do not have a membrane immediately beneath the brick, but use a chemical-resistant bond coat. These floors are usually installed in food and beverage industries, and other light industrial applications such as bottling and packaging areas of dairies and breweries, pharmaceutical and electronic clean rooms, bakeries, and cereal, coffee and meat processing plants.
The third type is light-duty floors in which the brick and tile are set in sand and cement setting beds, with only the joints between the tile and brick being of chemical-resistant mortars and grouts. These floors can sustain occasional spills of corrosive chemicals, foodstuffs, and many cleaning and sanitising compounds. They are not recommended for areas that are constantly wet. Typical applications include laboratories, cheese cutting and packaging areas, and commercial and industrial kitchens.
Conclusion
Aesthetically attractive, chemical-resistant and sanitary floors are available for solving virtually any flooring problem attributable to process chemicals and the use of cleaning and sanitising agents. The conditions to which the floor will be subjected must be carefully examined so that the proper system is specified. All flooring systems discussed above have excellent performance histories in a host of applications.
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