- Listed: April 3, 2019 12:48 am
What’s more, a surface retarder will give you greater control over the depth of exposure, allowing you to achieve the desired finish. Unlike concrete set retarders, they allow the rest of the concrete to cure normally, without affecting the setting rate or strength gain. When you are ready to expose the aggregate by hosing or high-pressure washing, the depth of aggregate reveal is more uniform with minimal pop-outs. The best time to apply surface retarder is after you’ve completed all finishing operations and the bleedwater has dissipated. Apply surface retarder evenly over the surface using a low-pressure sprayer or roller.However, if extreme wind or rain is expected, you should protect the surface with plastic sheeting.
An easy way to visually monitor where you’ve sprayed is to use a pigmented surface retarder, which contains a tracer dye that allows you to see your progress. How do you know when it’s time to wash off the surface?
Generally, the window is anywhere from 12 to 24 hours after application. If the depth is greater than desired or the aggregates begin to come loose, wait a bit longer before exposing the aggregate. The depth can also be affected by the length of time the retarder remains on the surface, concrete finishing methods, and the amount of water pressure and scrubbing action used during removal.
Glow In The Dark Rocks Glass Aggregate In Concrete Countertop | Duration 4 Minutes 8 Seconds
Using a wood float or broom finish will allow the retarder to penetrate more deeply and give you greater exposure. Because surface retarders are water-based, they can be safely applied outdoors and in areas with low ventilation. Any spilled product or overspray can be washed away with water or soaked up with absorbent material. Another application is to facilitate the polishing of newly placed concrete. Do not use surface retarders on vertical concrete or on surfaces treated with shake-on color hardeners.
You can also apply surface retarders to integrally colored concrete to achieve striking color contrast with the exposed aggregate. Get other ideas for achieving special effects with exposed aggregate. If you’ve never used a surface retarder before, here are some basics to help get you started. Surface retarders, also called surface “deactivators,” are applied to fresh concrete to chemically delay the set of the surface mortar. Because surface retarders work their magic by stopping the hydration process down to a controlled depth, the underlying concrete will harden properly while allowing easy removal of the surface paste later. Don’t seal the concrete first or apply curing compounds, which could prevent the retarder from doing its job.
Test a small area to determine if the depth of retarded mortar is at the desired level. Once the concrete is ready, remove the surface paste with a garden hose, a stiff broom, or a pressure washer. If you allow the surface to harden longer, aggregate exposure will become difficult and may require sandblasting. The depth of exposure will primarily depend on the surface porosity of the concrete when the retarder is applied, with deeper exposures produced on more open or porous concrete. What precautions should you take when using surface retarder?
In addition to exposing aggregate, surface retarders can also be used to create a roughened bonding surface for the application of concrete toppings. A surface retarder will soften the surface cement paste, reducing polishing time and the amount of heavy grinding needed. The dense surfaces produced by color hardeners will inhibit retarder penetration. However, you can still expose the aggregate on existing concrete by abrasive blasting. In addition to aggregate, surface retarders can also be used to expose other embedments, such as crushed shells or glass.
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It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. The term basalt is at times applied to shallow intrusive rocks with a composition typical of basalt, but rocks of this composition with a phaneritic (coarse) groundmass are generally referred to as dolerite (also called diabase) or gabbro.
It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. The most common uses for this rock are as aggregate in highway construction, railroad ballast, and tile.
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