Using the right concrete mix
Concrete is typically easier to place and finish with slumps greater than those either specified, designed, or both. While specifications for large commercial projects often limit how much water can be added to the concrete mix, there are often no slump limits or controls over the amount of water added for small commercial and residential projects.
Adding water to the concrete mix
Many times, three or more gallons of water per cubic yard is added to the concrete to improve workability, with the intent of making it easier to place and finish. However, the addition of this much water causes any number of problems, including segregation, reduced strength and durability, and increased shrinkage and cracking.
Use of admixtures
Some concrete producers add mid- or high-range water reducers to the mix to help mitigate these risks. Although this is an improvement, these mixes may still result in some form of segregation if the slump is excessive. Increased segregation causes headaches for contractors because it makes the concrete more difficult to pump and finish.
Control Flow Concrete
Control flow concrete is a new category of concrete that was designed to alleviate these concerns. It gives concrete producers the ability to create a flowing concrete (with a slump flow between 16-25 inches), using standard mix proportions. These mixes do not require special aggregates or increases in powder contents, and are not as sensitive as some self-consolidating concrete mixes.
It’s also easier for concrete contractors to work with control flow concrete. There’s no need to add water on the job site, since the concrete is designed from the start to meet a specific flow level. Control flow concrete eliminates unwanted segregation, which improves finishability and pumpability. This helps provide the owner with more durable, quality concrete with increased strength and reduced shrinkage and cracking. CONCERA® admixtures enable the production of control flow concrete.
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