Concrete sealer should only be placed on a concrete slab, not brick, tiles or stone. The properties in the concrete sealer work only for the porous surface of a properly poured concrete patio. The sealant protects the finish and also keeps moisture from migrating to the surface. Various products have different application times and may depend on whether the concrete patio is outdoors or under a covered roof. Some sealants may not be applied if the concrete patio has a color agent in the mix. In these cases the colorant must be fully cured.
Two Types of Sealer
There are two basic types of concrete sealer, acrylic- and solvent-based. Acrylic-based sealers seal the top of the concrete and do not penetrate into the patio. Solvent-based sealers literally work their way into the pores of the concrete. Multiple coats of the sealer can penetrate the full depth of the concrete patio in some product applications. In most applications a solvent sealer allows the patio to breath or exchange air from below the slab to the surface. The solvent sealer stops the movement of the moisture. Acrylic sealers stop all air movement and water from entering the top of the concrete patio. Check the manufacturer's specifications for the type of sealer for your application. A general rule of thumb is to use an acrylic sealer for slabs that have added color in the concrete. Solvent sealers may interfere with the colorant and cause an unappealing chemical reaction to the color.
When to Apply Solvents
Typically, solvent sealers are sprayed onto the surface of the concrete patio before it is fully cured. This may be as soon as the concrete is finished and is still soft to the touch. Other solvents may not be applied until several days later, but the concrete still appears green in color. The patio should be covered with a plastic sheet to retain the sealer and cause the concrete to dry or cure very slowly. The manufacturer's directions must be followed for the desired results.
Acrylic sealers, because they create a top seal on concrete, may be applied well after the concrete patio is cured. Applying the top sealer too soon can trap moisture inside the slab, and cracks or breaks can form. Concrete patios that have a colorant may take even longer to fully cure before any seal can be used. If the acrylic sealant is applied too soon to a colored patio, the acrylic may bleed into the dye and cause an unwanted reaction. This could result in muted colors or a bleaching effect to the patio. Bleaching is when a white powder-like substance forms on the top surface of the cured concrete patio. Acrylic sealer often is left exposed to the air so it can cure rapidly. In most cases, the new patio must be fully cured before any acrylic top sealer can be applied. Curing rates of concrete patios or slabs will depend on environmental conditions. Dry, hot areas cure concrete faster than cool, wet climates.
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