Concrete surfaces that are to be coated with a polymer floor coating or system require preparation to insure proper adhesion to maximize the performance and service life. An acceptable concrete surface should be free of loose concrete, contaminants, laitance and should be uniform and sound.
The basic procedure for preparing a concrete surface to receive a polymer floor system includes the following.
- Visual inspection of the concrete prior to surface preparation
- Cleaning to remove loose concrete, materials or other contaminants that can inhibit adhesion of the system.
- Profiling to produce best anchoring and maximum adhesion.
- Repairing surface irregularities to permit the application of a uniform coating system.
A visual inspection should be conducted of all concrete surfaces for signs of concrete defects, cracks, physical damage, chemical damage, contamination and presence of moisture.
Concrete that is loose, unsound or deteriorated must be removed to a point where sound concrete is exposed. Depending upon the extent and depth of the repair, cementitious materials from the Terrafuse product line or polymer mortars from the CTM product line may be used to restore the concrete.
There are several methods available to clean and prepare concrete surfaces for the application of a polymer floor coating system. Depending upon the degree of contamination some surface preparation methods may remove contaminants sufficiently to receive a coating system, whereas some methods and degree of contamination require washing, scrubbing and rinsing of the concrete surface prior to surface preparation. The primary goal of the surface preparation method is to create a sound profiled surface that is free of laitance and contaminants. Refer to the table below for a list of surface preparation methods.
|Detergent Scrubbing||Removing oil, grease, and loose materials for other preparation methods||CSP 1||Removable contaminants limited to water soluble and water emulsifiable products.|
|Low Pressure Water Cleaning||Removing dirt, dust and loose contaminants||CSP 1||Removes loose materials or contaminants only|
|Acid Etching||Removing concrete paste and traces of grease and oil. Low profile exposure of surface||CSP 1-3||Hazards of acid use. Limited to low profile preparation only. Does not remove grease. Requires neutralization, rinsing and drying.|
|Grinding||Removing coatings, build up deposits, smoothing irregular surfaces.||CSP 1-3||May not provide adequate profile. Requires thorough dust removal by vacuum.|
|Abrasive Blasting||Removing surface contaminants and providing a range of profiles||CSP 2-4||Large particulate volume generated. May damage or deface concrete surface.|
|Steel Shotblasting||Removing dirt, laitance, sealers, coatings, and other materials and producing a range of profiles||CSP 2-8||May not remove thick, soft, or elastomeric products. Accessibility to corners and tight spaces.|
|Needle Scaling||Removing coatings and brittle encrustations||CSP 5-8||Low production rates. Impact damage to sound concrete.|
|Scarifying||Removing contaminated concrete and thick, brittle coatings. Leveling concrete by removing high areas||CSP 4-9||Cutters leave profile and may cause micro cracking of concrete.|
|High Pressure Water Jetting||Removing laitance, efflorescence, dirt, water soluble contaminants and producing a range of profiles||CSP 6-9||Possible concrete damage and water damage to contents or surrounding areas|
|Scabbling||Removing thick, brittle coatings, contaminated or weak concrete and producing a deep profile.||CSP 7-9||May cause micro cracking. Difficulty in removing soft or elastomeric coatings.|
Patching and repair of surface irregularities of concrete surfaces to fill gouges, surface air voids or transitions to other adjacent areas or finishes may be performed using polymer mortars from the CTM product line.
Cracks in concrete may be categorized as structural or non-structural. Non-structural cracks are the most common and appear as fine spider web cracks or larger more severe cracks that are generally wider, jagged and irregular shape. As a general rule, if a crack is wider than the width of a credit card, consult a concrete structural engineer to determine if the crack is structural. Most non-structural cracks may be filled with ECT-CF Epoxy Crack Filler that is specifically designed for crack repairs. Cracks may also be filled with a flexible joint filler when thicker or elastomeric flooring systems will be used.
Elastomeric crack isolation products such as ECTM may be applied beneath a rigid polymer flooring system. This flexible under layer absorbs the movement of minor cracks without transferring the crack through the more rigid polymer flooring system. When a crack isolation membrane is used, cracks should be filled with an elastomeric caulking and may also be reinforced with fiberglass to help distribute stress loads created from movement.
Some polymer floor coatings are tolerant to moisture in concrete and on the surface, but most are not. Since concrete is a porous material, moisture can move through the pore structure and cause harmful effects on non-permeable polymer coatings. The use of proper vapour barriers beneath a concrete slab greatly reduces moisture vapour transmission. The period of time required to allow excess moisture to leave a new concrete surface is 28 days from time of placement, however, this does not imply that the surface is suitable to apply a polymer coating. If a system is being used in an environment where moisture content will affect the performance, test methods as in the table below may be used to determine the moisture content.
|Test Method||Acceptable Range|
|ASTM F1869 – Standard Test Method for Measuring Moisture Vapour Emission Rate using Anhydrous Calcium Chloride||15g/24hr/m² (3lb/24hr/1,000 ft²) max|
|ASTM F2170 - Standard Test Method for Determining Relative Humidity in Concrete using Probes||80% max|
If moisture issues are determined, systems designed to reduce moisture vapour transmission can be used to prevent potential polymer floor system failures. Penetron VB225 moisture vapour emission reduction systems are effective systems that can be applied directly to a prepared concrete slab prior to the installation of a polymer floor system when moisture vapour readings are above the acceptable range indicated in the table above. For time sensitive situations where a polymer flooring system needs to be applied on a concrete surface promptly, Penetron VB225 may be applied to concrete 5-7 days after concrete placement for on-grade or below-grade applications.
For additional information or assistance regarding surface preparation or moisture issues, contact us prior to starting a project.