What lies beneath01 August 2004

Temperature changes, static requirements, liquids, impact, abrasion and chemicals can all affect a floor's performance. Add static electricity to the mix and the result can be potentially explosive.

Resins are often chosen in preference to concrete because they offer good resistance to the effects of industrial chemicals, particularly acids. Synthetic polymers provide high levels of resistance to a wide range of chemicals and additionally enhance impact and wear resistance, as well as offering an impervious barrier to protect the sub-floor. However, it should always be borne in mind that the heat resistance of synthetic resins varies depending on specific systems chosen, such as epoxy, polyurethane or vinyl ester. Therefore, knowledge of surface temperature is critical at specification stage.

Low film-thickness synthetic resin systems less than 1mm would normally only be installed in areas subject to light industrial use such as pedestrian traffic, whereas for heavy forklift traffic a screed of up to 8mm or thicker might be needed. Medium thickness systems greater than 2mm would be used for heavy rolling loads including fork truck traffic. For very heavy usage a system thickness of greater than 4mm would generally be used. FeRFA (The Resin Flooring Association) produces a comprehensive guide to the selection of synthetic resin floors, which is available at www.ferfa.org.uk. British Standards also offer guidance on the thickness of floor systems.

Users' specific performance requirements are the key factors when choosing an effective and fitfor- purpose flooring system. This should be purpose-designed to meet the service needs. A correctly specified resin system can provide up to 20 years' longevity - more typically, under the influence of economic choice, seven to ten years may be the norm. While system thickness is not the only guide to the floors, it can be a good guide to life expectancy.

Preparations

A thorough inspection of the sub-floor is essential to identify any potential weaknesses, which must be addressed prior to the specified system being applied. A maximum strength of 25 N/mm (typical) is needed to support most resin systems. Surface laitance must be removed, ideally by shot blasting or scarification. However, while scarification is a more aggressive method of preparation and will remove a higher degree of contamination, it will leave a heavier texture on the concrete slab. Therefore, a thicker resin system will be needed to overcome this heavy surface texture. Hot compressed air treatments may be required if the sub-floor has previously been contaminated with oils. This will ensure adhesion is achieved over these areas and will eliminate the possibility of the oil bleeding through the resin finish after application.

In industrial areas, resin floors have traditionally been viewed as workhorses, supporting the workings of an environment with the sole objective of protecting an area with a heavy-duty finish. Environments are undergoing change with a greater emphasis on design and appearance, and this has led to a new era in flooring. Attractive finishes are starting to emerge including coloured coated quartz and coloured acrylic flakes. The most selective formulating can use aliphatic-based resins, which provide enhanced colour stability and UV resistance, so permitting the use of pale, pastel and bright colours.

Safety factors

Wet areas need careful consideration to ensure an effective flooring system is installed. One of the most important factors in these environments is slip resistance. This is achieved by the introduction of a coarser texture, created by aggregates incorporated within the floor system.

Another factor in the flooring of wet areas is the product's ability to tolerate moisture and avoid breakdown when exposed to constant damp conditions. For wet areas, floor finishes can be installed at builds from 1mm to 8mm, depending on the user's requirements.

Dry areas often have a lower requirement for slip resistance than wet areas and therefore smoother surface finishes can be used. The slip resistance of smooth finishes under dry conditions is generally excellent but can depend on the type of footwear and dry surface contamination.

Cleanability is an important factor, particularly in industries such as food processing. Different resin systems can tolerate different cleaning regimes. For example, thick polyurethane screeds and vinyl ester resins can withstand steam cleaning, but not all types of resins and coating can. Floor finishes are now available with the addition of antimicrobials (such as Flowcrete Ultrafresh HF, which contains Ultra-Fresh - an EV and VS FDA registered antimicrobial additive which can kill E coli, listeria and even the MRSA bacterium).

Slip resistance can have an effect on cleanability. These two factors need to be considered carefully as part of the specification process to ensure a floor is going to be fit for purpose.

Flexible choice

Flexibility needs to be considered in areas where there is vibration and movement, including sites housing moving machinery. Flooring systems are available that offer a degree of flexing that can cope with this type of movement.

With regards to joints, it is not generally possible to overcoat moving joints without allowing for the movement that will inevitably occur. However, flexible jointing compounds can be used to breach the moving area. If they are applied correctly, they will form a seamless joint in the resin floor and through to the concrete sub-base.

Resins combined with fine aggregates can be used that are designed to take impact and create a robust and strong surface. This type of system is often called on for areas such as engineering workshops, where metal can fall to the ground, chip the floor and expose the substrate, if the right finish has not been applied. Increasing floor thickness and the use of resin screed formulations typically greater than 4mm will help to prolong the longevity of the floor and its aesthetics.

Dealing with static

Another consideration is antistatic flooring, which is an important feature for explosive environments, powder handling and the electronics industry. Pharmaceutical production plants are just one example of areas notoriously vulnerable to the build-up of electrostatic charges. A potentially lethal combination of a hard surface used by nylon-wheeled trucks, busy human traffic and combustible powder processing has led flooring manufacturers to focus their attention on new antistatic products to combat this problem. Antistatic flooring systems vary and can include the construction of a network of copper strips, along which static electricity dissipates to a series of earthing points.

While there is no simple guide to chemical resistance, in general terms resins can withstand the effects of industrial chemicals - particularly inorganic and organic acids - and their resilience is much higher than concrete. Synthetic polymers provide high levels of resistance to chemicals and additionally improve impact resistance, as well as offering an impervious barrier protecting the subfloor. Some systems can also withstand highly aggressive chemicals used in specialist industries. (For example Flowcrete Flowcoat SK is specifically designed to withstand the aviation hydraulic fluid Skydrol.) The ultimate chemical resistance of a resin floor is usually only achieved after full curing has taken place (typically seven days) so it is important to protect the floor from spillage immediately after it has been laid.

FeRFA's Guide to the Specification and Application of Synthetic Resin Flooring states that by paying attention to floor design, for example the provision of adequate drainage and good housekeeping standards, excellent service life can be achieved under conditions of aggressive chemical spillage.

Highs and lows

General-purpose epoxy compositions are unsuitable where very high or low temperature applications are concerned. A minimum 9mm thickness of rigid polyurethane screed will assist in resisting thermal shock temperatures ranging from -40 to 125ºC. Additionally, 9mm polyurethane screeds will be resistant to very sudden changes in temperature (thermal shock) - flexible polyurethane screed systems are more appropriate.

Specifications for lower temperatures in general are easier to specify than higher ones. Where temperatures exceed 100ºC, then polyurethane concretes (such as Flowcrete Ultrafresh HF) are the most effective solution where high impact and abrasion resistance are also required, for example in heavy duty food plants.

Generally, a resin finish can be applied to new concrete once it has dried so that the relative humidity is below 75%, as measured in accordance with BS8203. Conventionally this leads to delays of up to 28 days. The use of specialised primers acting as a surface dampproof membrane can enable resins to be applied within a quarter of this time.

Once installed, selective formulating can ensure that most resin systems are suitable for light pedestrian traffic after 24 hours. However, heavyduty traffic should be kept off the floor for 48 hours. The ultimate chemical resistance will only be achieved after full curing has been achieved (typically seven days). Temperature is a major factor in achieving these guidelines.

Of course, with so many factors involved in flooring selection and specification, this is only an outline guide of some of the issues. To ensure accurate specification of a flooring system that is fit for purpose, it is advisable to call a professional flooring manufacturing company and let their technical service department guide you through the correct process of specifying flooring.

Andrew Gwyther is a director of flooring manufacturer Flowcrete plc Flowcrete T: 01270 753000 www.flowcrete.com

SOE

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