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Surface preparation and priming

 

Superior Epoxies systems are formulated for application over a variety of substrates provided that proper procedures are followed in preparation. If a particular application cannot be found in this guide, or if your are not sure how to accomplish a specific task as described, please call your Superior epoxies & Coatings representative NOTE: A sample placement is always a good idea when evaluating field conditions.

 

Moisture Testing

Moisture in concrete and vapor emission is an important factor when determining the suitability of a slab for resinous toppings or coatings. These conditions may adversely affect the bond or final performance of epoxy systems.

 

Moisture traveling through concrete in the form of water or vapor carriers salt particles which will rise to the surface of concrete slabs. These salts are visible as dusting concrete or laitance. When epoxy systems are placed on surfaces in this condition, there is no way for these transitory salts to escape. Eventually, they build up at the interface between the concrete and the resinous material and will eventually blister the epoxy. If this blister is broken, a white powder and/or water will be present beneath it. As a result the bond between the concrete and epoxy will be lost.

 

To test concrete for moisture prior to applying Superior Epoxies Epoxy Coating.

 

Tape a 2 x 2 piece of non-breathing rubber or plastic sheet to substrate.

Apply heat to draw moisture. If outside, sunlight is sufficient. If inside or overcast, a heat lamp is required.

Leave in place for four hours.

Remove mat. A slight darkening and/or beads of moisture on the concrete and mat respectively, indicates too much moisture.

 

New concrete floors should be acid etched in several small test areas using a 10% muriatic acid solution. The areas should be flushed with clean water to remove any traces of the muriatic acid and laitance. The floor should then be allowed to dry completely. A polyethylene sheet or rubber mat is then taped to the floor and allowed to remain in place for 48 hours. If moisture gathers under the polyethylene sheet, epoxy should never be applied to concrete in this condition.

 

Existing concrete floors should be tested in the same way. Acid etching will also determine the existence of clear sealers and coatings on the surface. If the muriatic acid solution does not bubble vigorously, a sealer coating is present and must be removed. After mechanically removing the coatings, proceed with the test for moisture as previously described. If no moisture is detected under the mat, work may proceed with preparation of the entire surface and application of the epoxy system.

 

New Concrete

New concrete slabs must be allowed to cure for at least 28 days. (Consult your Superior Epoxies Representative for exceptions). During this period, the concrete goes through the hydration process and allows any excess water to leave the concrete mass. For slabs on grades, it is imperative that the concrete contractor makes sure that a vapor barrier is placed and is not punctured during the pouring process. Additionally, only curing agent compatible with the Superior Epoxies epoxy must be used and the finish on the concrete must meet specifications. A wood float or light steel troweled finish is the best surface profile for application of resinous toppings or coatings. As a general rule, curing compounds should not be used if resinous toppings or coatings are to be applied. Curing agents may be used, but they will have to be evaluated on a project basis to determine if they will have to be removed or if they are compatible with Superior Epoxies epoxies.

 

Once the water content/vapor emissions test is complete, Acid etching of the entire floor area may proceed. Acid etching must be accomplished on all new concrete surfaces. Care must be taken when diluting the acid. Always wear protective clothing, gloves and eye protection or use approved respirators to ensure proper ventilation. Always add the acid to the water.

 

The proper technique for acid etching should be followed. The acid solution should be sprinkled over the entire surface using a polyethylene sprinkling can. Do not pour the solution over the surface and spread it around. Once the solution is sprinkled on the floor, it should be scrubbed into the surface with a stiff bristle broom to remove any loose concrete, cement paste or laitance. The etching process should be observed closely to determine areas where vigorous bubbling does not occur. These areas will have to be mechanically scarified and etched again. The solution should then be rinsed with generous quantities of water. DO NOT ALLOW THE ACID SOLUTION TO DRY ON THE SURFACE. Salts are formed by the acid reacting with the concrete and are very hard to remove once they are dried. These salts can adversely affect the bind of epoxy to concrete.

 

Once the rinsing has been completed, the floor should be mopped dry and allowed to stand for 24 hours before proceeding further. Remember, the temperature has an effect on the evaporation of water from the surface. Adequate heat or additional time may be required to insure that the surface is completely dry. The moisture content test should be conducted again to insure that the surface is dry prior to applying the epoxy coatings.

 

Epoxy products require sound concrete to insure long lasting service life. The surface should be sounded with a hammer or chain dragged to indicate hollow areas requiring repair.

 

Any irregularities in the surface, depressions, or high points, will be transmitted to the final finish of epoxy coatings. These irregularities must be removed. It is very important to remove the high points since the coating will be at minimum thickness at these points. Grinding or rubbing stones may be used. (See Superior Safety Etch)

 

Old Concrete

After conducting the moisture/vapor test to determine suitability of the surface for epoxy application, surface preparation may proceed. Structural soundness of the concrete should be determined by sounding concrete with a hammer or chain dragging on the surface. Patching and repair materials should be used where required. Once structural soundness has been determined, preparation of the surface may proceed. Removal of contamination, curing agents, sealers and existing coatings is critical. Numerous methods are available to accomplish this task. The method selected (i.e., shot blast, sand blast, water blast scabling, etc.) must insure complete removal of existing materials. Exposure of sound concrete and small aggregate particles will occur but should not be polished or unnecessarily rough.

 

Superior Epoxies epoxy may be installed over old, existing coatings if they are well bonded and their chemical composition can be identified. However, do not apply a solvent based epoxy to an alkyd or urethane coating because poor inner-layer adhesion will result and cause the epoxy to delaminate. Solvent-free, 100% solids epoxy systems can even lift old coatings from the surface because of the tension produced during the curing of the epoxy.

 

Oil and chemical-soaked surfaces must be cleaned with solvents, degreasing agents or by mechanical means. The chemicals should be identified and Superior Epoxies contacted for specific recommendations.

 

Wood Surface

Superior Epoxies epoxy products maybe used over wood surfaces. On floors, never place epoxies over plank or stripped flooring. Apply over exterior-grade plywood (C plugged) with an extended glue line. DO NOT USE MARINE-GRADE PLYWOOD. As a general rule, the thicker the plywood, the better the application. As a minimum, use plywood. Insure that it is adequately fastened to the floor joists using ring shank or coated nails fastened every six inches (6). Joists should be staggered and covered with 3 Fiberglass tape coated with a compatible low modulus epoxy.

 

Metal Surface

Metal surfaces must be structurally sound and rigid. All oil, grease and other contaminants must be remove and allow to dry. Wipe surfaces treated or untreated with Methyl Ethyl Ketone (MEK) or chlorinated solvent prior to application of epoxy system.

 

The sufficiency of the preparation of a metal surface can be partially determined by the use of the water surface tension test. This test checks the surface tension of the metal. Individual droplets of distilled water are applied to the surface with an eyedropper. If the surface is not clean, the water will not spread; it will react more like a drop of water repelling on wax paper and will remain in a hemispherical shape. If the surface is clean and the surface tension is low, the water will spread into a thin film wetting a relatively larger area.

 

General Priming Guidelines

As a general rule, when applying epoxy toppings or patching mortars, the same material that is used as a primer is used for the binder as well even when working with epoxy mortars in a gel consistency.

 

Primers are used to insure that there is enough liquid epoxy (which acts as the adhesive between the mortar and the concrete at the interface to form a moisture barrier between the epoxy mortar and substrate.

 

Before placing epoxy toppings or mortars, all substrates should be primed unless a minimum amount of aggregate is used to create a wet or soupy mixture with good wetting abilities.

 

 

MIXING CONSIDERATIONS

 

The mixing ratio of epoxy systems must not be altered under any circumstances.

 

Temperature Effects

Epoxy components should be stored at moderate recommended temperature (generally 60F-75F) at least overnight prior to use. The viscosity of the epoxy is rather sensitive to temperature. When the temperature is below the recommended use temperature, the components will be more viscous, become difficult to mix, present problems in application, and will take longer to cure. Conversely, the viscosity of the epoxy components will be reduced when the material temperature is above the recommended use temperature. The components will be easier to mix, but the material may become too thin or soupy for the intended application. In addition, the reaction rate will be increased, resulting in shortened available time for application of the mixed material. Optimum results will be attained if the temperature of the components is within the recommended use temperature range at the time of mixing. Remember, the cure time cannot be changed by adding more curing agent (hardener) to the mix. Therefore, when cold weather (40F-50F) approaches and an epoxy compound appears to be setting or curing too slowly, DO NOT attempt to speed up the set time by the addition of excess hardener. Also in the summer, when temperatures are higher (90F-110F), DO NOT attempt to slow the setting time which might appear to be too rapid by using less hardener. The only effect that either of these action will have is to create a compound which will not attain stated physical properties.

 

Heating Methods

Several methods are available for heating epoxies to a temperature where effective mixing can take place. The simplest method is by storing it in a heated area overnight before use. When such storage space is not available and more rapid heating is required, ovens, hot air and electrical heaters can be used with caution. Another method and one which can be better controlled, is to immerse the epoxy component containers in a hot water bath.

 

Superior Epoxies materials and most epoxies used in the construction industry should never be heated over 120F because the working life would be too short and degradation of the components may occur.

 

Cooling Methods

When cooling is required for proper application, viscosity and adequate working life, the following cooling methods are recommended, store material in shade, refrigerator, refrigerated room, or in a cold water bath. In no case should the material be cooled to the extent that adequate mixing cannot be achieved.

 

Aggregate Temperature

Aggregates are used with mixed epoxy components to produce epoxy mortars and grouts. Aggregate loading usually makes up an equal or grater proportion of the mix, therefore, their temperature will greatly affect the consistency, workability and curing of the mixture.

 

Example 1: If the epoxy components are heated for a cold temperature application and then mixed with aggregates that are cold, the ease of mixture workability will not occur.

 

Example 2: If the epoxy components are cooled to the recommended temperature for a high temperature application and then mixed with aggregates that are very hot, adequate working life and desired consistency will not be achieved.

 

Substrate Temperature

The temperature of the substrate will not only affect epoxy workability, but also the initial and final cure of epoxies. As a rule, initial cure of epoxies is affected by temperature in the following ways:

 

Initial (thin film) cure time is usually 6 times pot life at 77F.

Every 18F drop below 77F will cause the initial cure time to double.

Every 18F rise in temperature above 77F will cut the initial cure time in half.

 

Mixing

Part A = Epoxy Resin

Part B = Curing Agent

Mechanical Mixing of the epoxy components is the most efficient and effective method. Thorough hand mixing is difficult and takes longer than machine mixing. This additional time may be critical considering the relative short pot life of most mixed epoxy resin systems.

 

The most accurate method of proportioning is to use the proportioned unit supplied by Superior Epoxies so that the entire contents of both containers are mixed together. If smaller quantities of mixed epoxy are needed, the specific proportioning ratio should be accurately measured. These ratios only expressed by volume.

 

Due to exothermic heat generated by epoxies in a large mass and the accelerating affect on cure time, the components should be mixed in a container that has a flat bottom and is big enough to hold 1 to 2 times as great as batch size. A clean and dry plastic pail makes a suitable mixing container. A paint mixing paddle (Jiffy Mixer) driven by a low speed electric or an air powered drill should be used for the mixing. For mixing larger volumes of epoxy, a mechanically driven paddle mixer (Muller Mixer) is preferable since this type of equipment forces the material together and scrapes the sides of the drum. Mixing should continue until the compound is homogeneous. This usually takes two to ten minutes, depending upon the restrictions of pot life, viscosity, density, flow characteristics of the epoxy and type of equipment used.

 

Aggregate Use and Mixing Epoxy Mortars

After the resin and hardener have been mixed, immediately mix in the selected aggregate. The specified aggregate should be clean, dry and properly graded silica or quartz sand. A very workable sand has a small amount of fines passing through a No. 70 sieve and usually has little or no material retained on the No. 12 sieve. For the best results in the production of epoxy mortars, a blend of 20-50 mesh sand works well. This is especially true when working with high aggregate loading factors, 3, 4, or 5 parts of aggregate to 1 part mixed epoxy.

 

The epoxy mortars used for overlays and patching consist of 1 part liquid binder filled with anywhere from 1 to 4 parts (by volume) of the graded sand. The amount of sand depends upon the viscosity of the binder, particle shape, and void characteristics of the aggregate.

 

The following chart shows the desired loading of aggregate to different epoxy viscosities.

 

Aggregate

Consistency Viscosity By Volume

Low Viscosity2,000 maximum3-4 parts

Med. Viscosity2-10 maximum2-3 parts

GelPaste1x1x1/2 parts

 

NOTE: For some epoxy mortars, the proportion of aggregate to liquid binder may be as high as 9:1 by volume. This is done by the use of very selected and well graded aggregates ranging from coarse stone down to very fine sands (200 mesh) whereby, most of the voids are filled in with small size aggregate so less epoxy is used.

 

Once everything is in the mortar mixer, mixing should continue only long enough to get a completely wet aggregate and uniform mix. The addition of the aggregate generally yields a longer working life. An extended mixing time may develop heat and shorten the time available for application.

 

Aggregate Broadcasting

To achieve a non-skid coating, apply the epoxy coating by brush, short nap roller, or spray at the specified product coverage rate. Broadcast sharp sand, emery, or carborundum on the first coat while still wet. The size and amount of aggregate used will dictate the type of skid proofing achieved. If desired, a second application of the epoxy can be used to seal the surface.

 

To achieve a topping, apply epoxy binder by squeegee, short nap roller or capable sprayer at the rate of 80 square feet per gallon. Broadcast the aggregate at the rate of one pound per two square feet using a spreading machine or by hand. After the binder sets, sweep or vacuum excess aggregate and repeat above process by applying binder at the rate of 100 square feet per gallon. Continue this process until the desire thickness is achieved and use one pound of aggregate per two square feet on the final cost.

 

 

     

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