Testing - Concrete Mix Design, Quality Control and Specification - page 134

The second of these assumptions will be examined in detail later.
The first assumption is probably correct in so far as the purpose of the
test is to detect quality variations but is not necessarily correct if the pur-
pose is to establish whether the concrete is basically satisfactory based on
non-strength-related performance parameters such as freeze-thaw resis-
tance, shrinkage, or penetrability, which will be discussed later in this
chapter.
It may well be impracticable on most projects to use other forms of
testing for quality control purposes, although rapid wet analysis and
simple resistivity testing has been so used. However, especially when we
are dealing with standard mixes from a premix plant or a special mix
designed for a specific purpose, it is certainly practicable to carry out
a much wider range of tests to initially verify a new mix design and to
repeat a wide range of tests at say annual, or six monthly, intervals for
standard mixes. An excellent example of this is the shrinkage of concrete
in the Melbourne, Australia. For many years structural designers had been
concerned about excessive shrinkage but the only action resulting from
this concern was to prohibit the use of pumped concrete on some proj-
ects and limit sand percentages on others. However, in 1977-1978 CSIRO
(the Australian Government Commonwealth Scientific and Industrial
Research Organisation) carried out shrinkage tests on a range of standard
Melbourne area pump mixes and showed a wide range of variation with
clearly definable causes. It then became practicable to specify a limiting
shrinkage and in most cases to permit the use of pumped concrete since
the tests showed that some pumped mixes had a lower shrinkage than
some nonpump mixes (the factor involved being the influence of the coarse
aggregate).
Similar action is now needed in respect of splitting strength, permeability,
durability, abrasion resistance and also workability (other than slump),
segregation resistance, bleeding, and surface finish characteristics. These
were all matters on which we were flying as blind as we used to be on
shrinkage at the time of writing the first edition. In the intervening years
there has certainly been substantial action in respect of durability and
penetrability (with the latter seen as the best available criterion of the
former).
7.3 COMPRESSION TESTING
Considering now the accuracy and convenience of compressive strength
as a routine control, the situation is not as simple as was thought 20 or
30 years ago. In Australia we are fortunate to have the world's first and
most highly developed NATA. We have a better system than most other