Bricks, Masonry, Asphalt and Concrete - aggregate concrete
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10-01-00, 04:40 PM
How to do decrative aggregate concrete steps
10-02-00, 11:18 PM
Depending on elevation preciseness the form work is either set dead on or a little low. In the first instance the mix is struck off below the forms (how much varies with the size of the aggregate). In the latter case the added aggregate raises the elevation.
The aggregate is seeded (sprinkled) into the still plastic mix. It's floated (and steel troweled depending on the timing) to fully embed it and cover it with a slip coat. Seed timing varies with the size of the aggregate. Large aggregate is seeded after strike off and before bullfloating or darbying. Small aggregate is seeded near the time when finishing would normally occur. Two treatments for exposing exist. Retarder is sprayed on and exposing occurs the next morning. Wait 2-4 hours for initial set then using a garden hose with a fine mist nozzle start exposing the aggregate. Done at the proper time the slip will wash away in a milky stream. Too soon and sand or the aggregate are dislodged (the same for too much water or pressure). As exposing continues a fine soft broom is used to assist the process. Wait too long and a powerwasher is needed to expose the aggregate.
Another option is to order exposed aggregate mix. Seeding is not necessary, but, it is more expensive and the aggregate selection is fixed. (Colored aggregates can cost as much as $700.00 per ton, so custom batching may be out of the question. Otherwise custom batching may be an alternative).
Free advice: put some time into aggregate selection. Slippery stone can be a killer when wet or with wet soles. If a sealer is used ensure that it's rated for exposed aggregate.
The aggregate is seeded (sprinkled) into the still plastic mix. It's floated (and steel troweled depending on the timing) to fully embed it and cover it with a slip coat. Seed timing varies with the size of the aggregate. Large aggregate is seeded after strike off and before bullfloating or darbying. Small aggregate is seeded near the time when finishing would normally occur. Two treatments for exposing exist. Retarder is sprayed on and exposing occurs the next morning. Wait 2-4 hours for initial set then using a garden hose with a fine mist nozzle start exposing the aggregate. Done at the proper time the slip will wash away in a milky stream. Too soon and sand or the aggregate are dislodged (the same for too much water or pressure). As exposing continues a fine soft broom is used to assist the process. Wait too long and a powerwasher is needed to expose the aggregate.
Another option is to order exposed aggregate mix. Seeding is not necessary, but, it is more expensive and the aggregate selection is fixed. (Colored aggregates can cost as much as $700.00 per ton, so custom batching may be out of the question. Otherwise custom batching may be an alternative).
Free advice: put some time into aggregate selection. Slippery stone can be a killer when wet or with wet soles. If a sealer is used ensure that it's rated for exposed aggregate.