Petrographic examinations
are commonly performed on fine and coarse
aggregates used in concrete. These
examinations follow the guidelines of ASTM
C295. Petrographic
examinations may be performed on concrete
aggregates for a number of reasons.
A full petrographic examination can be
performed to completely characterize the
aggregate source. This examination
will determine the amounts of the various
rock and mineral constituents present in
the aggregate. This examination will
also characterize the quality, condition
and chemical stability of the individual
constituents. This type of
examination is often performed to
determine if a particular aggregate source
is suitable for use in concrete. More
focused petrographic examinations can also
be performed on concrete aggregates.
Some examples of this are given below:
-
Determination
of the amount of a given constituent (ie.
pyrite, chert, coal, shale) present in
an aggregate sample
-
Determination
if an aggregate source contains
constituents that may be susceptible
to alkali-silica reactions in
concrete.
-
Identification
of constituents that may be
susceptible to pop-out distress when
used for concrete in freeze/thaw
environments.
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