Assessing Cryogenic Testing of Aggregates
for Concrete Pavements
CHARLES KORHONEN AND BRIAN CHAREST
INTRODUCTION
numerical durability factor that, when used as a
Despite the remarkable advances made in con-
criterion for aggregate selection, helped improve
crete technology over the past several decades,
pavement performance. The MDOT (1989) freeze
freezing and thawing deterioration of concrete
thaw method MTM 115 evaluates the dilation of
pavements is still of great concern to state high-
concrete beams subjected to an environment con-
way officials. The development of air-entrained
forming to ASTM C 666, Procedure B (ASTM 1990).
concrete in 1938 and more recently the introduc-
The method cycles nine moist-cured concrete spec-
tion of mineral and chemical admixtures to the
imens between 4.5 and 17.8C and back again by
concrete market have dramatically improved the
freezing them in air and thawing them in water in
performance of cement paste. However, there are
3 hours. Cycling continues until the concrete is
other important factors affecting the durability of
exposed to 300 cycles or until it expands beyond a
concrete besides those pertaining to the paste.
certain limit, whichever occurs first. Much of
When water in coarse aggregate freezes, it can
MDOT's coarse aggregate comes from glacial de-
create sufficient stress within the aggregate itself
posits, which means that physical properties and
or within the surrounding cement paste to cause
therefore freezethaw characteristics of the aggre-
the pavement to crack. Therefore, materials engi-
gate may change from location to location within
neers, faced with the problem of finding durable
a given borrow pit. Thus, relying on a freezethaw
aggregates, have made this a focus of considerable
test method that can require up to 70 days to run
research. Nevertheless, freezethaw induced crack-
becomes impractical when answers may be need-
ing continues to happen on fairly new highways,
ed each day.
resulting in extensive and costly rehabilitation.
During the fall of 1990, CRREL and MDOT en-
Usual methods of identifying aggregates able
tered into a cost-sharing partnership to explore
to endure freezethaw rely on service records and
innovative ways for rapidly differentiating dura-
on laboratory testing. A growing problem with
ble from frost-susceptible aggregates. This part-
service records is that sources of aggregate known
nership was made possible through the authority
to be freezethaw durable are being depleted,
of the U.S. Army Corps of Engineers Construction
particularly in densely populated areas. Added to
Productivity Advancement Research (CPAR) Pro-
this, the quality of aggregate from even a proven
gram. Working with assistance from Michigan
source can change and environmental laws con-
Technological University (MTU), MDOT was to
cerning the mining of aggregates are becoming
select aggregates from 20 different sources and
more restrictive. Thus, laboratory testing is be-
conduct conventional freezethaw evaluations,
coming increasingly essential, but the time re-
concentrating on aggregate moisture condition-
quired to run current test methods frequently
ing and aggregate size. The CRREL portion was to
exceeds the available design period. A faster and
test samples from the same 20 sources using a
simpler test method would be better.
proposed accelerated test method that freezes the
The Michigan Department of Transportation
aggregate particles by immersion in liquid nitro-
(MDOT) started freezethaw testing of coarse ag-
gen and thaws them by immersion in hot water.
gregates in 1954 and by 1976 had established a
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