|  Retarders
Retarders, as the name would imply, act just the opposite
from accelerators. They slow down the set to allow for proper
placement or to overcome the faster hydration that would be
expected in war- weather, helping to assure quality. The PCA
notes that the many problems contractors face in the field
- trucks held up by traffic, onsite delays and equipment malfunctions
- are other reasons to consider the use of retarders.
Retarders are used by decor contractors
to give them mom time to do stamping and finish work. Ralston
says that his company is realizing the advantages of step
retardation, using the prepackaged admixture on site when
second loads come in. "The guys are like ants on a Sugar
Daddy waiting around to do the work," he says. "And
you can use admixtures to get better control of local weather
conditions - if your concrete is coming from 50 miles away,
they may not know your local situation and you'll have to
adjust for it on site."
Scofield's Harris, who has worked on
installations with Ralston, explains it this way: A third
of the concrete can be poured, then a retardant added to the
rest. After a second third is poured, mom retardant is added
to the remained. This allows time to do finish and detail
work.
Costs
Ojeda adds that use of step retardants can also help contractors
avoid short load charges. Indeed, the costs of admixtures
must be considered when planning a project. When it comes
to costing out a project, says Ojeda, the cost of the concrete
represents 10%-20%, and the cost of the admixture is about
5%-10% of that, so the total cost of admixtures represents
only a small portion of the project. However, he says, this
small investment can modify the concrete to meet the total
needs of the project, saving time and labor and helping eliminate
expensive callbacks and repair work. "So don't cut corners,"
Ojeda says. "If it will help, use an admixture."
Admixtures vary widely in cost, adds
Seymour, but ultimately, the cost is immaterial, as the specifications
of the job are paramount. When it comes to concrete, he says,
"performance is key."
Levig would agree. "When I use
an admixture," he says, "I do not think of how to
cut costs but rather how to get a higher quality concrete."
Getting
the right product
"Them is something we call putting the concrete to sleep,
and admixtures can give you flexibility of set time so you
can dictate what you need to do," says Harris.
When it comes to knowing what
to use and how to use it, suppliers are key. Lafarge's Seymour
notes that decor contractor should work with suppliers to
get the right mix design for the job.
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