Exterior Surface Concrete Paint Systems

Textured Emulsion Paints

Textured emulsion paints are quite popular in the market and are widely used on cement surfaces. They have higher film-forming capability compared to standard flat-surfaced emulsion paints. To balance the low permeability of these higher film-build paints, the pigment volume concentration in the paint formulation is generally increased. However, normally, despite high pigment volume concentration, textured paints are very durable on walls. The particle size of commonly used textured additives typically ranges from approximately 0.2 to 2.0 mm and can sometimes be even larger. Generally, refined sands or coarse paint fillers are used to produce finer textured or sand-textured paints, while gravel stones, silicates or coarse-particle carbonates are used to produce coarse textured or aggregate paints. During the formulation stage, care should be taken in the classification of the textured material to ensure that it is consistent with the application method and that the correct packed appearance is achieved in the dried film. Sand-textured emulsion paints are produced in a manner similar to conventional-type paints.

However, the textured additive can be added after pigment dispersion is achieved and before the required color matching adjustments are made.

The formulation of sand-textured paints is somewhat different from that of flat topcoats, and is particularly achieved with lower pigment amounts and higher additions of filler-type texturizing materials. This does not affect the opacity of the paint film. Because these types of topcoat paints have higher film build, this compensates for any loss of opacity. A typical formula is shown in Table 1 and is applied as one or two coats by brush or spray. The pigment volume concentration of this formulation is approximately 48%. The application validity for pigment volume concentration of textured paints has not yet been established. However, it is assumed here that the addition of coarse-particle sands or aggregates does not significantly affect the pigment volume concentration of the pigment filler-polymer combination used in a given formulation. Aggregate-textured paints are formulated as shown in Table 2. This paint is applied with a plaster trowel or specially designed spray gun. Their coloration can be achieved with self-coloring mineral aggregates, colored marbles and similar materials. Or they can be colored with flint aggregates that are synthetically coated, typically using polyurethane-based paints. Very small amounts of pigment powder can be added during production to control the final color tone of the paint. Production is done by simple mixing; grinding or dispersion is not required.   A high aggregate-to-binder solids ratio (approximately 8:1 as seen in the example) should be optimal in such a manner that the polymer coats and binds the aggregate particles and provides adequate wet adhesion. Polymer swelling tends to form a film that partially masks the topography of the dried paint. Talc used in the formulation increases the water resistance of the dried film. The wetting agent is an important additive added primarily to improve application properties when applied with mortar.

New and Dry Exterior Concrete Surfaces

At the stages following construction, new and dry exterior concrete surfaces will be obtained when there is no excess moisture remaining on the cement surface. This formation interval will depend on the cross-sectional thickness of the concrete or plaster and the severity of the external environmental conditions, and this period can be in 1-12 month intervals. At this stage, there are no limitations in the types of paints that can be applied to concrete surfaces. However, as protective measures against unwanted wetting and the reactivation of alkali salts, the paint systems to be applied must have alkali resistance. Where alkyd resins of this type with inherently low alkali resistance, such as vegetable-oil-modified alkyds, are to be applied, a resistant binder primer or undercoat should be applied. These binding primers also have an important role in consolidating weathered cement surfaces. Three main classes of paints are applied to dry cement surfaces. These are chlorinated rubber-based paints, vinyl copolymer-based paints, generally used where high durability and water impermeability are required, and textured or non-textured emulsion paints as previously described.

Other paint types such as epoxy, polyurethane and alkyd-based can also be applied, but their use is not widespread compared to the classes mentioned above.

However, in general, the use of these polymers does not cause any particular problem in wall paints and are normally all formulated as low-build paint systems as satin or matt topcoats. It is clear that in general-purpose use as paints applied to concrete or plastered walls, emulsion-based systems are the most frequently used systems. Chlorinated rubber and vinyl systems, on the other hand, are used in specially desired main applications requiring high resistance to water and contaminants and exceptional durability. The formulation of textured emulsion paints for new and dry cement surfaces is approximately the same as that for paints used on damp surfaces. However, in non-textured emulsion paints, since high permeability to moisture is not required, lower pigment volume concentration levels of approximately 30-35% are acceptable. This reduction in pigment volume concentration for dry cement surfaces enables better durability properties to be achieved. A pigment volume concentration of 28% is given in Table 3 for a white exterior facade emulsion paint formulation. M. Namık Kayaalp / Chemical Engineer / Ecelak Boya Kimya Ltd. Şti.

References 1. Flick, E.W., Water-based Paint Formulation Noyes Data Corp. New Jersey, 2. Newton, D.S. (Ed.), Paint Technology Manual Part 4, Chapman and Hall, London 3. Paint Formulation, J.Boxal, George Godwin Ltd.-London 1980.