AASHTO M 224-91 pdf free download
AASHTO M 224-91 pdf free download.Use of Protective Sealers for Portland Cement Concrete.
Epoxy Resin—Epoxy may be considered a coating or penetrant depending on the percentage of solids in the formulation. The two-component epoxy resin system forms a sealer that is tough, hard, and resistant to chemicals that normally attack roadway surfaces and weathering. Before curing, epoxy has a tendency to “pinhole,” permitting later entrance of water and salt solution into the underlying concrete. Experience indicates the use of suitable primer may alleviate this. Also, application of the material during that part of the day when the concrete is cooling helps prevent pinholing. If the epoxy is formulated as a coating, flaking or peeling can occur due to a difference in thermal expansion of the coating and the concrete or to improper surface preparation. The protective film formed by these materials reduces frictional properties. The use of a suitable aggregate spread over the freshly applied coating greatly improves frictional properties. Epoxy systems require skill in handling and application. It is essential that the recommendations of the manufacturer be followed precisely for both application procedures and equipment. Special materials will be required for cleaning of equipment. Most persons are allergic to contact with epoxies; therefore, recommended safety practices must be followed carefully.
C’oal Tar Epoxv—Coal tar resins form surface coatings that are hard and durable. They are relatively resistant to many corrosive and abrasive environments and are durable under exposure to weather. They appear to function best on roadway surfaces when filled with sand and other suitable aggregate. These materials contain curing agents and strong solvents that may cause allergic reactions. They must be handled with caution; recommended safety precautions must be followed. These materials are naturally dark to black in color and may not be desirable in some locations.
Linseed Oil—Linseed oil applied to concrete surfaces penetrates and forms a partial barrier to water. It is therefore not subject to traffic abrasion and it does not materially change the original frictional properties of the concrete if applied at the proper rate. Linseed oil may be applied as solution. Experience indicates that the solutions are more effective and longer lasting than are emulsions, probably due to redispersion of the linseed oil applied as an emulsion, when subjected to salt solutions. These materials are easily applied with simple, readily available equipment and require no specialized knowledge or skills. Safety hazards are minimal; only routine precautions for handling and using flammable liquids are necessary with the solvent types. For best results on new concrete surfaces, the concrete should be allowed to dry for about 30 days prior to the application of the compound. To remain effective, concrete surfaces should be recoated annually for 2 years followed by a biannual or triannual schedule of treatment.
Tar Primer and Seal—Tars applied to concrete surfaces form a coating that is an effective surface barrier to water. Usually a primer must be used because of wetting difficulties on concrete. These materials may be applied in solution or softened by heat. Due to relatively poor resistance to sunlight, weather, and abrasion, these materials should be covered by a suitable bituminous mix.
Silanes and Siloxanes—These materials are classified as penetrants. Unlike other sealers, these materials do not truly seal the concrete, but react chemically with the concrete, both at the surface and in pores and capillaries, to form a hydrophobic layer, which is repellant to water. They can be applied in one coat.
Methacrvlates—These materials may be described as a coating or penetrant depending on the formulation. Two coats are usually required to get proper sealing. The surface to be treated must be dry and free of oil, grease, and loose material. Time needed between coats will vary according to ambient temperature conditions.
Sodium Silicate—This material is a penetrant in the form of an aqueous solution. Concrete surfaces must be clean and dry at the time of application. The material should not be applied at temperatures below 4°C (40°F) or during rain.AASHTO M 224-91 pdf download.
