Developing New Low-Temperature Admixtures for Concrete
A Field Evaluation
CHARLES KORHONEN, BRIAN CHAREST, AND KURT ROMISCH
Conventional practice
INTRODUCTION
Current winter concreting practices have re-
mained unchanged for many years. Concrete in-
During March 1994, an innovative way of pro-
gredients must be heated to melt all ice and to
tecting fresh concrete from freezing was field
create a mix temperature that is well above freez-
tested in northern Michigan at the Soo Locks in
ing; the substrate on which fresh concrete is
Sault Ste. Marie (run by the U.S. Army Engineer
placed must be thawed; and the concrete must be
District, Detroit). Instead of using the customary
kept warm and moist long enough to assure ade-
insulation or heated enclosures, special chemical
quate strength.
compounds were added to the concrete to help it
Construction standards require that normal
gain strength while its internal temperature was
concrete be kept at or above 5C (ACI 1988) until
below the freezing point of water. Two prototype
it has cured. As temperatures drop to this mark,
chemical formulations, antifreeze admixtures,
finishing operations take longer and forms can-
were developed as part of the Corps Construc-
not be stripped as fast as they can during the
tion Productivity Advancement Research
summer. The strength gain of concrete is slowed.
(CPAR) program. This field test intentionally al-
At a few degrees below zero, not only is the hy-
lowed fresh concrete to cool below freezing with-
dration rate of cement slow, the mix water begins
out any attempt being made to insulate or heat it.
to turn into ice. At 3C, 90% of the water will
freeze (Korhonen 1990). If freezing occurs, the
BACKGROUND
concrete may lose half its strength. Figure 1
shows the effect of temperature on the strength
Construction Productivity Advancement
of normal concrete.
Research (CPAR) program
Freezing, however, is a threat for only a short
CPAR allows Corps research laboratories,
time. As concrete matures and water chemically
such as CRREL, to work with private industry on
combines with cement, the quantity of freezable
Research and Development that has potential for
water diminishes to the point that freezing the
advancing the art of construction and for being
concrete once will not damage it. Most concrete
of value to Corps activities. The intent of CPAR is
develops this level of self-protection by the time
to catalyze improved construction technology
it reaches a compressive strength of 3.5 MPa
through cooperative, cost-shared ventures. Such
(ACI 1988), which, for normal concrete cured at
a venture resulted in the development of the two
10C, can happen in a day.
admixtures described in this report.
The procedures used today to protect concrete
These admixtures were developed under two
from freezing and to assure adequate strength do
independent projects--Master Builders, Inc.,
produce concrete that meets construction needs
and W.R. Grace & Co. entered into separate con-
for strength and durability. However, this protec-
tracts with CRREL in 1991. Each project was suc-
tion can be expensive. It has been estimated that
cessful in bringing a practical antifreeze admix-
the U.S. construction industry spends 0 mil-
ture to the threshold of commercialization.
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