ambient temperatures down to 7C (20F) with an
ded steel reinforcement, or to steel on which
application dosage of up to 60 mL/kg (90 fl oz/
concrete is placed
cwt).
Be cost-effective
In an effort to expand upon the success of
Further, to avoid the necessity of conducting
Pozzutec 20 and to develop the long-sought freez-
long-term testing of experimental admixtures to
ing protection admixture, Master Builders and
determine that they meet these requirements, the
the U.S. Army Cold Regions Research and Engi-
decision was made that only chemicals currently
neering Laboratory entered into a cooperative re-
being used in concrete be considered for initial
search project. This project was conducted under
evaluation. This decision provided us with rea-
the authority of the Corps of Engineers Construc-
sonable assurance that the chemicals have already
tion Productivity Advancement Research (CPAR)
been tested for their effect on concrete. As experi-
program. Because the Federal Government is a
ence was gained with this new technology, other
big buyer of construction services and the Corps
chemicals could be added to the study. It was also
of Engineers uses a lot of concrete, a new winter
decided that the initial low-temperature goal
would be set at 5C (23F), with 10C (14F)
admixture would produce savings for the Gov-
ernment and provide a benefit to the U.S.
being a possible ultimate objective, and that the
economy. This is the final report of Fiscal Year
concrete cured at these low temperatures should
1990 project "Freezing Temperature Protection
gain strength at least as rapidly as normal con-
crete at 5C (40F), the accepted low-temperature
Admixture for Portland Cement Concrete."
limit for winter concreting in the United States
(ACI 1988).
Objectives
The two prime objectives of this study were to
Finally, to ensure reasonable continuity during
explore the low-temperature performance of
the nearly two years of laboratory testing, both
Pozzutec 20 and to develop a prototype admix-
MB and CRREL used the same cement, air en-
ture that would protect fresh concrete from freez-
training agent, and plasticizer. The cement se-
ing while increasing the rate of cement hydration
lected was an ASTM Type I cement from Blue
when the internal temperature of the concrete is
Circle Cement, Tulsa, Oklahoma, with a Blaine
below 0C (32F).
fineness of 3460 cm2/g (Table 1). A Type III ce-
One important constraint in developing low-
ment was used at CRREL for some Phase I mix-
temperature admixtures for concrete is that no
tures (Table 1). The air entraining agent was a
standards of acceptance criteria are available.
neutralized vinsol resin, MB-VR, and the plasti-
Chemical admixtures are currently classified by
cizer was a high-range water reducer, Rheobuild
1000 (naphthalene sulfonate-formaldehyde con-
ASTM C 494 into seven categories of set-control-
densate, calcium salt), both from Master Builders.
ling and water-reducing admixtures. The catego-
Each party used its local aggregates and water.
ries include Type C, accelerating, and Type E,
The coarse and fine aggregates used by CRREL
water reducing and accelerating admixtures, each
tested at 23 1.7C (73 3F), well above freez-
ing. It was therefore necessary at the start of this
Table 1. Chemical composition
project to define a freezing protection admixture.
of Type I and Type III cement.
Freezing protection admixtures were defined as
chemicals that should:
Type I
Type III
Depress the freezing point of water
Compound
(%)
(%)
Promote strength gain of concrete at low
SiO2
20.85
20.95
temperatures
Al2O3
4.75
5.44
Not interfere with concrete strength gain
Fe2O3
2.26
2.36
at normal, above-freezing temperatures
CaO
63.92
62.57
K2O
0.70
0.75
Maintain workability of the concrete in
MgO
2.34
2.16
freezing conditions
SO3
3.14
4.20
Achieve reasonable concrete set times
C3S
58.0
43.6
(this does not necessarily mean accelerated
C2S
16.0
27.2
set times)
C3A
9.0
10.4
C4AF
7.0
7.2
Produce freezethaw-durable concrete
LOI
1.18
1.09
Not react unduly with silica aggregate
Na2O (Eq)
0.87
0.80
Not contribute to corrosion of embed-
2
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