Rockmax presents this information based upon industry technical bulletins and many years of experience with flooring systems. This document is offered purely as a guideline and, since no two floors are alike, each one must be evaluated for its particular needs. The cost of surface preparation far outweighs the cost of the materials for the flooring system and therefore, it is extremely important to evaluate the substrate properly.
The major cause for floor failure is an inadequate bond to the substrate, usually caused by insufficient or improper preparation and/or evaluation. No coating or topping will adhere unless it is applied to a properly prepared floor surface that is sound, dry and free of contaminants. Dirt, dust, grease, oil or spilled product (chemicals, food, etc.) form a barrier to adhesion and must be eliminated. Old paints, sealers and coatings should be totally removed or expertly tested for adhesion. In the case of new concrete floors, they must be cured for a minimum of 28 days at 31°C, and the laitance and/or resinous curing membranes must be removed.
Moisture also causes many floor failures. Every floor must be evaluated to determine the rate of moisture vapor transmission (MVT). Rockmax has determined that, for most of our flooring systems, the maximum MVT is 4 lbs. per 1000 square feet (1.81 kg per 93 m2) over a 24 hour period. Rockmax does offer special thin-film sealing systems that are “breathable” and will withstand a greater rate of MVT.
Moisture comes through the concrete from several sources: the curing process, excess water used in the concrete mix, an absence or improper installation of a “below the slab” moisture vapor barrier, unexpected increase of water in the sub-soil caused by a broken pipe or sewer line or a “water table” near the under side of the concrete slab. Increased moisture vapor pressure can cause polymer flooring systems to deform, creating blisters, bubbles and even delamination from the slab due to osmotic vapor pressure.
It is important to note that MVT can change from one area of the slab to the next. It is therefore important to take several readings. Moisture can be measured by several methods: The Plastic Sheet Method (ASTM 4263), which tells you yes or no, but not how much moisture; an Electronic Moisture Meter, which gives qualitative results but will pinpoint problem areas; or the Calcium Chloride Test (ASTM F-1869) which is a better quantitative test, and should be performed across the slab. To avoid false results, the area should be climatized first, and all curing compounds removed.
If the MVT is greater than 4 lbs. (1.81 kg), contact Rockmax for assistance on choosing a permeable system or to investigate other possible options.
Floors subjected to Thermal Shock (constant cycling of hot and cold temperatures) are also a concern for choosing the proper flooring system. In this case, as well as high MVT, it may be advisable to choose Rockmax PU concrete flooring system as a barrier coat or as an entire system.
Once the MVT has been determined, the time comes to choose a method by which to prepare the substrate. Several factors are involved in choosing the proper preparation method. These include:
1. Environment – The greater the service requirement, i.e., heavy traffic, the more the bond will be challenged.
2. Time – Facility production times vary, and time constraints alone may dictate the method chosen.
3. Budget – Certain preparation methods are more expensive and labor intensive than others. The customer’s budget will often dictate the method purely on cost.
4. Available Power and Accessibility – Certain equipment requires high voltage power and, at times, may be too large or heavy to be used in certain situations.
Creation of a surface profile is required to achieve a mechanical bond. The ideal profile is 10-20 mils (0.25-0.50 mm) (similar to 60 grit sandpaper). For coating applications less than 40 mils (1.02 mm), a milder profile may be desired, as deeper profiles may be visibly detectable, and affect the appearance of your flooring system.
Depending on the condition of your floor, one or a combination of the following methods may be used to prepare the surface for coating or resurfacing. Please remember that these are general guidelines – the flooring professionals at Rockmax will be happy to advise you on your specific preparation requirements.
We have divided the floor preparation methods into three main categories: Chemical Cleaning, Mechanical Cleaning, and Heat Cleaning.
1. Acid Etching is chemical treatment of concrete by attacking with Hydrochloric (muriatic) acid (commercial grades are to be diluted with 2 to 4 parts water) to remove laitance and embedded dirt. Laitance is a scum, a thin layer of cement and silt deposited on the surface during the finishing process of concrete floor construction. The acid etching opens the pores of the concrete for better adhesion. Pre-wet the floor, and do not allow the acid to dry. Allow to foam for a few minutes, then scrub into the substrate with a stiff broom. All acid must be flushed with water, then neutralized, using an alkaline floor cleaner where strong fumes cannot be tolerated, or where metal exists, followed by methods 5 and 6.
2. Stripping is the removal of existing coatings (paints, urethanes, etc.) by attacking them with an exotic chemical/solvent based mucous type compound, usually containing methylene chloride. All old paints should be removed for good adhesion of a new coating.Extreme caution must be used with chemical/solvent based strippers. HIGHLY TOXIC. Combustible and/or Flammable. This method is to be done at the applicator’s own risk, and Rockmax does not sanction it due to its inherent dangers.
3. Solvent Degreasing is the “safety” solvent attack of any grease or oil embedded in the concrete. Oil and grease will prohibit adhesion of flooring system, and therefore must be removed. Solvent degreasing is the first step to their removal. A citrus and water-based, environmentally friendly cleaner/degreaser, for this purpose. Many other solvent degreasers are at least mildly toxic and combustible. Continue to use caution. If “safety” solvent degreasing is not totally successful, the next step is:
4. Liquid Caustic Soda Scrubbing will attack extremely stubborn greases and oils embedded in concrete. A 12.5% solution of caustic soda and water can be used to remove animal fats and oils. Caution must be taken using this method, as caustic soda can cause serious burns if it comes in contact with skin or eyes. The residue must be thoroughly flushed from the surface with a diluted acid solution (see above), followed by:
5. Alkaline Soap Scrubbing neutralizes any residual acids used in the etching process, removes spent strippers or degreasers, and washes off any remaining surface dirt. We recommend our concentrated Liquid Industrial Detergent, a non-toxic, biodegradable, neutral pH, odorless, non-staining degreaser and cleaner.
6. Pressure Washing is high pressure water used to remove deep down dirt and wash off any remaining chemicals or residues by putting them into suspension with water pressure from 500 to 3000 psi (3448 to 20685 kPa). Hot water or steam can be used at lower pressures, and at times is more effective against oil, grease, and animal fats.
The simple test to determine if oil and grease have been removed from the floor is to sprinkle droplets of water on the floor. If they bead up, the floor is not ready. If they soak in, the contaminants have been removed from the top layer of the substrate.
1. Shot Blasting profiles the concrete by steel shot impacting the concrete at extremely high speed. This process eliminates three main reasons for coating failure: trapped moisture, trapped contaminants, and an improper surface profile, which prevents the coating from penetrating the pores of the concrete. Since it uses no water or chemicals, and is dust-free, it is an environmentally safe method of preparation. The size and impact speed of the blasting shot can be varied to provide the proper surface etch or profile, depending on the condition of the floor and type of coating and/or resurfacing material specification desired. Note: When using shot blasting for thin-film floor systems, be aware that blast lines may be visible.
2. Scarifying is the removal of contaminants and deteriorated concrete by the use of rotating steel teeth. This method is useful for removing semi-soft materials from floor surfaces.
3. Scabbling removes the top layer of concrete by the impact of air driven cylinders. It will take care of problems caused by concrete weakened by deeply embedded contaminants. However, this is a very slow process.
4. Hand or Air Scrapers remove soft material in small floor areas. They are useful when large power equipment is economically unfeasible.
5. Diamond Grinding removes contaminants in areas where hand-scraping is ineffective. This procedure can be done wet or dry, depending on the equipment used and the project requirements. Large diamond grinders, up to 30″ (76.2 cm) dia., are also available. Use dust vacuums when dry grinding.
6. Wire Brushing removes loose dirt and soft substances from the floor surface. It works well on rough surfaces and metal. A variety of wire brush equipment is available.
7. Mechanical Chipping Hammers or Jack Hammers remove contaminants from cracks to prepare for patching. To assure proper repair of cracks and adhesion of filling material, the crack must be as clean as possible. This type of equipment is slow, but very aggressive; and can therefore be useful to remove contaminants that other equipment cannot.
After any mechanical method of preparation, all dust and loose particles must be completely removed by a thorough sweeping and vacuum cleaning. Power equipment makes this job easier, and is preferable if space allows. If a wet process was used, the area should first be scrubbed with plenty of water. Certain primers can tolerate damp substrates, while others cannot. Please contact Rockmax for advice on which to use. It is sometimes advisable to utilize a mechanical method of preparation prior to a chemical method, or vice versa.
Our last method, which can be broadly termed “Heat Cleaning”, includes propane torching. This method is excellent for removing heavily saturated oil and grease from floors, and for removing fibers protruding from concrete, after the “shot-blasting” of a fiber reinforced slab.
Propane torching draws petroleum based oils and/or animal fats out of concrete to the surface where they are carbonized. It will remove oily contaminants, which are deep-seated in the floor. Further chemical cleaning is necessary following this procedure. Note: Cracks and joints that are non-moving may be pre-filled before the flooring system is installed using Rockmax EI. Moving joints can be covered with the flooring system, but should then be saw-cut and filled with Rockmax PUseal, a flexible 100% Polyurethane elastomeric, to allow the flooring system to move with the concrete.
Note: Steel must be shot blasted to near white and the primer applied within 4 hours before oxidation begins.
Remember to follow all safety precautions for any type of method used. Read all MSDSs, and dispose of all waste in accordance local regulations.