concrete from freezing when other chemicals are
concrete from damage when the weather gets bit-
not available. Although concrete made with these
terly cold. Normal concrete is damaged as soon as
chemicals may not develop much strength early
the temperature drops a fraction of a degree below
on, Table 5 shows that the concrete recovers at
freezing.
least 75% of its potential strength once thawed. In
For long-term applications, antifreeze admix-
the situation where concrete can be placed and re-
tures should be studied for their effect on the
turned to when the weather turns warm, these
freezethaw resistance of concrete. Preliminary
chemicals should not be overlooked.
data at CRREL and elsewhere suggest that the
The chemicals shown in Table 4 are used in a
addition of certain chemicals into concrete can sig-
wide variety of manufacturing processes, from
nificantly increase its freezethaw resistance. One
pharmaceuticals to food additives and, as such,
explanation for this improvement is that much of
are readily available most anywhere. Using them
the antifreeze probably remains in the pore water
or the ones in Tables 3 and 5 in concrete is quite
solution; it may not combine with the hydration
simple. Weigh enough water for one batch of con-
products. This, in turn, depresses the freezing
crete, dissolve the appropriate chemical or chemi-
point of the concrete so that it experiences fewer
cals in that water, one chemical at a time, and then
freezethaw cycles than would normal concrete
follow standard concrete mixing procedures after
exposed to the outside environment. Another pos-
that. Once the concrete is placed, consolidated,
sible mechanism is that the dissolved particles
and finished, cover it with a sheet of plastic for 37
somehow prevent the mixing water from fully
days to minimize evaporation. Because of differ-
expanding, even when fully frozen. Laboratory
ences in cements and how they react with various
measurements of freezing mortars show that mor-
chemicals, the field results could vary from those
tars containing antifreeze produce less expansive
of this report. Thus, concrete mixes made with any
pressure than do normal mortars. Less expansion
chemical shown in this report should be tested
translates into less damage. Thus, antifreeze admix-
before use. It is recommended that trial batches of
tures might have the residual benefit of making con-
the concrete to be used in the field be made with
crete more durable.
the chemicals and evaluated for strength gain at
Data also suggest that antifreeze chemicals can
the temperatures expected in the field. Until fur-
increase the salt-scaling resistance of concrete
ther work is done, it is recommended that a mini-
pavements, bridges, and other structures subject
mum of 363 kg of Type I portland cement be used
to deicing salts. Preliminary studies conducted
per cubic meter of concrete, and that the w/c ratio
elsewhere show that concrete made with an anti-
should be no higher than those used in this report.
freeze admixture is more resistant to freezethaw
The aggregates should be ice-free.
cycling in salt water than is normal concrete. Osmo-
sis is one explanation for salt scaling. Deicing salts
create highly concentrated solutions on bridge
WHAT WE STILL DON'T KNOW
decks, for example. To equalize these concentra-
Additional work should be done to make opti-
tion differences, water may try to flow out of the
mal the combinations of chemicals used in this
concrete, creating considerable pressures and
study to improve concrete performance at lower
causing the concrete surface to spall. Finding the
temperatures. The work should include not only
right chemical dosage to reduce this pressure may
reformulating these chemicals and testing them
translate into huge savings in reduced repair bills.
for the best dosages, but it should include a search
Current guidance forbids placement of fresh
for other chemicals that can make concrete set up
concrete onto a frozen substrate to prevent a bot-
fast. Specific attention should be given to combin-
tom layer of concrete from freezing. Preliminary
ing the Table 5 chemicals with others to enhance
studies (Korhonen et al. 1997a) showed that con-
their performance in concrete.
crete can be placed on very cold crushed stone
An effort should also be made to determine the
without problem. Guidance on when normal con-
minimum chemical dosage required for protection
crete can be placed on frozen substrates needs to
against frost damage. Such a dosage would not be
be developed, both to avoid any freezing and to
expected to promote much strength at low tem-
determine how to thicken the concrete should
peratures, but it might become routinely used in
freezing be unavoidable. Work should also be
all winter concreting as a vaccine against unex-
done define the effect of various substrates on an-
pected cold. The findings in this study suggest
tifreeze concrete.
that even small dosages of some chemicals protect
Finally, the relationship between the tempera-
8
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