trial admixture produced a set time that was 20
existing admixtures used by the concrete indus-
min longer than that achieved with the Pozzutec
try today.
20 admixture. Other admixtures acted as set re-
10. At the 100-mL/kg (150 fl oz/cwt) dosage,
tarders, producing concrete set times in excess of
the EY-11 admixture produced a concrete that
those produced by admixture-free concrete. These
easily passed the ASTM C 666, Procedure A,
comparisons were drawn from mortar cured at
freezethaw test. The EY-11 concrete had a dura-
room temperature and made with 365 kg/m3 (611
bility factor of 96 at the end of 300 cycles of freez-
lb/yd3) of Type I cement.
ing and thawing compared to a durability factor
3. Pozzutec 20 did not contribute to the corro-
of 99 for admixture-free concrete.
sion of reinforcing steel embedded in concrete
11. At dosages of 60 and 100 mL/kg (90 and
submerged in sodium chloride solution. This was
150 fl oz/cwt), EY-11 was not found to contribute
true for both the 60- and 100-mL/kg (90 and 150 fl
to corrosion of steel reinforcing embedded in con-
oz/cwt) dosage.
crete submerged in calcium chloride solution.
4. At its maximum permissible dosage of 60
12. EY-11 was determined to be equivalent to
mL/kg (90 fl oz/cwt), Pozzutec 20 did not reduce
55.9 mm (2.2 in.) of insulation when the ambient
temperature is as low as 1C (30F).
the freezethaw durability of standard concrete
beams tested according to ASTM C 666, Proce-
13. The negative aspect of the EY-11 admixture
dure A. At that dosage, the durability factor of
is that it did not promote short set times as effec-
concrete made with Pozzutec 20 following 300
tively as did Pozzutec 20. The set time of EY-11
cycles of freezing and thawing was 99 compared
was approximately half an hour longer than that
to control concrete, which was also 99. A durabil-
with Pozzutec 20. Also, the EY-11 admixture did
ity factor of 80 is considered passing. At a dosage
not promote enhanced strengths to the same de-
of 100 mL/kg (150 fl oz/cwt), the durability fac-
gree as did Pozzutec 20 when concrete was cured
tor of the concrete dipped below 80 after 204 cycles
at room temperature. These are considered im-
of freezing and thawing.
portant productivity factors.
5. Pozzutec 20 at a dosage of 60 mL/kg (90 fl
14. The field tests clearly demonstrated that
oz/cwt) was determined to be equivalent to plac-
working with EY-11 required no new skills. The
ing 50 mm (2 in.) of fibrous glass insulation over
concrete was easily mixed at low temperature,
the concrete. This is the thickness of insulation
the admixture was dosed into the truck, as is
that admixture-free concrete would require to re-
normally done with some admixtures today, and
main above freezing for seven days at an air tem-
the concrete was finished in the usual manner.
perature very near freezing.
The major benefit was that, once finished, the
6. The critical freezing strength of concrete
concrete was not damaged by exposure to freez-
made with Pozzutec 20 is considered the same for
ing temperatures. The only protection used was a
admixture-free concrete. Pozzutec 20 does not
plastic sheet to cover exposed areas to minimize
adversely affect the strength at which concrete
moisture loss during curing. Because external heat
can first be frozen.
was not needed to protect the concrete, a tremen-
7. When used at its maximum permissible dos-
dous amount of thermal energy was conserved.
age of 60 mL/kg (90 fl oz/cwt), Pozzutec 20 was
The resulting concrete quality was excellent.
unable to promote strength in concrete cured at
15. The potential effect of being able to place
5C (23F) at the same rate as that in admixture-
concrete at temperatures below freezing is sig-
free concrete cured at 5C (41F). This finding
nificant. Pushing the winter concreting envelope
from the current 510C limit to 5C (23F) can
prompted the search for an improved low-tem-
perature admixture.
extend the "normal" construction season by over
8. The prototype admixture, code named EY-
two months in northern Michigan, such as at the
11, was selected as the potential improvement to
Soo Locks. Since the climate at the Soo is similar
Pozzutec 20 for use in freezing temperatures.
to that of the coldest areas in the conterminous
9. EY-11 at a dosage of 100 mL/kg (150 fl oz/
United States, the construction season should be
cwt) was able to promote strength in concrete
extendible by at least two months in the United
cured at 5C (23F) at the same rate as that devel-
States by using an admixture with the low-tem-
oped in admixture-free concrete cured at 5C
perature capability of the experimental admix-
(23F). This is considered a major advantage over
ture EY-11.
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