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Common problems in F-number measurement arise on many jobs. Following ASTM E 1155 "Standard Test Method for Determining FF Floor Flatness and FL Floor Levelness Numbers," is essential.
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During the summer of 1999, a concrete contractor placed an exterior parking lot for a commercial building in the Midwest. The concrete was air entrained and received a broomed finish, followed by 3 days of moist curing with plastic-coated burlap. Because some of the concrete set at a different rate...
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In structures for which rebar corrosion isn't an issue, calcium chloride is the most economical and effective accelerating admixture. It's widely used in a liquid solution in unreinforced pavements, residential foundation walls, and floors placed in cold weather. It helps concrete set and gain...
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Many building owners and contractors have reported experiencing project delays while waiting for slabs made with lightweight concrete to dry to the moisture-vapor-emission rate typically required by floor-covering manufacturers (3 pounds per 1000 square feet in 24 hours). Though we couldn't find...
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More than 441 million cubic yards of concrete will be placed in 2000. And the total in-place concrete cost? A whopping $88 billion dollars. That's up almost 13% from 1999. We gathered cement and concrete statistical data from several sources. Then, with the help of the Portland Cement Association...
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When constructing a floor, concrete contractors often unroll a sheet of plastic vapor retarder over the subbase and cover it with a blotter layer of compacted granular fill before placing concrete on the fill. But how effectively do vapor retarders resist punctures during construction operations?
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In bidding a job, concrete contractors have to estimate the duration of each concrete placement, which requires estimating the concrete's setting time. When cold weather, admixtures, or other factors delay setting and increase the time finishers must wait, the contractor starts losing money. But...
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Owners and engineers increasingly demand low-shrinkage concrete to reduce the number of cracks, crack width, and curling. Some engineers even specify shrinkage limits for submittals of concrete proportions.
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Over the years, we've had many contractors describe what they believed to be inferior specifications, but it was hard for us to tell if the problem was widespread. To evaluate a broad sampling of concrete specifications, we visited plan rooms in Baltimore, Denver, Detroit, San Diego, and Seattle...
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For contractors who place concrete floors that require coverings, the results of moisture-vapor emission tests can mean the difference between a project that remains on schedule and one that falls weeks behind. Consider the following scenario.