by Clayton DeKorne
Concrete is a heavy material and
any steps taken to make it easier to
work with are understandable. Unfortunately,
many finishers achieve
greater workability by asking the
driver to add more water to the mix.
When the slab cracks, the blame
passes from the contractor to the finisher
and, ultimately, to the supplier,
who usually winds up shouldering the
responsibility.
Suppliers go to great lengths to
avoid this problem. Most routinely
use air-entrainment agents, chemical
admixtures that form air bubbles, to
help decrease segregation (see "Glossary"
at the end of this article for italicized
terminology) of the mix. Many
automatically add superplasticizers,
another type of chemical admixture
that retards setting times and produces
concrete that flows better. In
hot weather,