SURFACE PREPARATION GUIDE

This method statement describes guidelines for evaluating concrete surfaces and their preparation prior to installing resinous flooring products. All substrates to receive Sika flooring products must be structurally sound, clean and at a minimum saturated surface dry (SSD). Proper surface preparation is a critical factor in the successful performance of applied resinous floor or wall systems.

Providing an acceptable substrate is the responsibility of the owner, the owner’s representative, or the concrete contractor unless specifically stated otherwise. The contractor responsible for the installation of the Sika flooring and wall systems shall be provided a substrate that is clean, durable, flat, pitched to specifications, SSD, and free of surface contaminants.

Surface contaminants must be removed prior to creating a surface profile. Contamination of concrete surfaces includes all materials that may affect the adhesion and performance of the coating to be applied. Examples include, but are not limited to, dirt, oil, grease, chemicals, curing compounds, etc.

The removal of these contaminants may be accomplished by the use of detergent scrubbing with a heavy-duty cleaner/degreaser, low-pressure water cleaning (less than5,000 psi), or steam cleaning. The concrete’s porosity and the duration of exposure play an important part in the cleaning/neutralizing of the contaminants.

Test the pH of the surface to ensure the contaminants have been removed from the concrete. The chemistry of concrete is alkaline in nature. Normal concrete should bein the range of 11 to 13. After decontaminating, test the floor in multiple locations using distilled water and paper. If the pH is 10 or lower, additional decontamination is needed to ensure a good bond. In areas where the contaminants cannot be eliminated, the contaminated concrete must be removed and replaced.

The common method to test pH at the surface of a concrete slab is to use a wide range of pH paper, its associated pH chart, and distilled or deionized water. Place several drops of water on a clean concrete surface, forming a puddle approximately 1 in. (25 mm) in diameter. Allow the puddle to set for 60 +/-5 seconds then dip the pH paper into the water. Remove immediately and compare to the chart to determine pH reading. Other pH testing methods such as pH pencils or pH meters are available and may be used to measure surface pH.

Weak or damaged concrete must be removed and surface defects such as blowholes and voids detailed. Use appropriate Sikafloor® SikaDur® and SikaGard® repair materials for repairing the substrate, such as filling blowholes, voids, and surface leveling (see chart 2-1). The concrete or screed substrate must be primed or leveled to an even surface. High spots must be mechanically removed, e.g. grinding.

Concrete substrates must be mechanically prepared to remove cement laitance, existing coatings, curing compounds, and achieve a profile that is clean, dry, and free from dirt, grease, oil, and any other surface contamination. Shotblasting, grinding or similar techniques are ideally suited for this work.

Shot Blasting is the industry standard for surface preparation of concrete. Shot Blasting means that a machine projects a large number of abrasives towards the surface of the concrete and in this way roughens the surface. A wheel in the machine uses centrifugal force to propel the abrasive against the concrete. The abrasives are then drawn back into the machine to be used again. The dust will be separated by the use of a dust collector.

Scarifying tools are used to plane a floor, prepare a concrete floor for further treatment, or remove the old resin-based coating to achieve a profiled open textured surface. A concrete scarifier is equipped with a cutting tool that rotates at very high speeds to tear the surface. Scarifyingcreates a great amount of dust so a capable vacuum dust collector must be used.

Note: Scarifying can damage and loosen the upper layer of the concrete. Therefore it is mandatory that a scarified surface must be shot blasted afterwards.

The International Concrete Repair Institute (ICRI) Guideline No. 310.2 (formerly 03732) has defined nine different guidelines for proper surface preparation, known as Concrete Surface Profile (CSP), and has developed profile replica blocks to give a visual point of reference for the user. The nine profile replicas of the CSP standards can be obtained from ICRI. Each profile carries a CSP number ranging from a baseline of 1 (no change to profile/remove loose debris)through 9 (very rough/exposed aggregate).

Sika’s Typical Recommendation: download the Surface Prep Guide PDF to learn more

To assess the moisture content of the substrate and determine if is acceptable to apply a concrete coating use one or several of the following test methods:

Pre-Test Conditioning - The substrate and occupied air space above the floor shall be at temperature and relative humidity expected under normal use conditions for a minimum of 48 hours prior to testing for moisture. If this is not possible, the test should be conducted at 75F +/- 10F and relative humidity of 50 +/- 10%.

Moisture Meter: ASTM F2659 - Standard Guide for Preliminary Evaluation of Comparative Moisture Condition of Concrete, Gypsum Cement and Other Floor Slabs and Screeds Using a Non-Destructive Electronic Moisture Meter. The test can get an instant and precise evaluation of the moisture conditions within 1.0” below the surface of the slab. This is done by using the Tramex® CME/CMExpert that gives a measurement of % moisture content by weight; a moisture map of the entire substrate can be recorded.

Relative Humidity: ASTM F2170 – Standard Test Method for Determining Relative Humidity in Concrete Floor SlabsUsing In-situ Probes. The Relative Humidity (RH) test involves drilling holes into the cured concrete and stabilizing for at least 72 hours prior to placing probes in the concrete and reading the results with a hygrometer.

Relative Humidity: ASTM F2420 – Determining Relative Humidity on the Surface of Concrete Floor Slabs UsingRelative Humidity Probe Measurement and Insulated Hood. This test method involves placing a purposely-made, thermally insulated hood onto the surface of a concrete slab thereby creating an entrapped and impervious air pocket.

Calcium Chloride: ASTM F1869 - Standard Test Method for Measuring Moisture Vapor Emission Rate of ConcreteSubfloors Using Anhydrous Calcium Chloride. The Calcium Chloride test involves placing a dish of calcium chloride covered by a plastic dome (adhered to the concrete) on the concrete and allowing the dish to remain in place between 60-72 hours. The calcium chloride absorbs any moisture vapor that transmits through the concrete within the plastic dome. The results of a calcium chloride test measure the amount of moisture absorbed and results are stated in pounds per 1,000 ft2.

Always consult the Sikafloor Product Data Sheets, Method Statements, or contact Sikafloor Technical Services for recommendations and procedures for testing.

One of the most critical environmental conditions of high-quality resinous coating quality is the dew point. Because moisture on a surface can lead to problems such as flash rust, poor adhesion, delamination of coating layers, procuring, degradation of a coating’s physical properties, corrosion beneath the coating, long term impact on the coating performance, and unmet expectations of a promised product feature.

The dew point is associated with temperature and relative humidity. A high relative humidity indicates that the dewpoint is closer to the current air temperature. Relative humidity of 100% indicates that the dew point is equal to the current temperature (and the air is maximally saturated with water). When the dew point stays constant and temperature increases, relative humidity will decrease.

The dew point is the temperature of an air-water vapor mixture at which condensation of water vapor begins, with the air becoming saturated. To allow a practical safety margin, the substrate temperature must be at least 5°F above the dew point.

To calculate Dew Point, read the air temperature on the left column and the measured relative humidity on the top line. Note the dew point at the intersection of the two values.

Concrete expands and contracts due to drying shrinkage and temperature changes. To control where this cracking occurs joints are placed in the concrete slab at a predetermined spacing. These joints are either saw cut (control) or preformed (isolation/expansion) to allow for these natural changes in the concrete that are dependent on varying ambient conditions.