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Class 3: Quantitative fundamental, to be used strictly in accordance with the definitions

in BS 5168: Glossary of rheological terms, e.g. viscosity, mobility, fluidity,
yield value.1

Such a division is helpful in that it clearly exposes the limitations of many of the terms,
and it will be useful to keep this in mind when reading this chapter.

1.2.2 Measurement of workability by quantitative
empirical methods

Many tests have been devised and used over many years to produce quantitative empirical
values in Class 2 above. They give a single measurement, and are therefore often referred
to as ‘single-point’ tests, to distinguish them from the ‘two-point tests’ which give two
measurements, and which we will describe later.

As long ago as 1947, twenty-nine single-point tests were described as the more important
of those developed up to that time (Glanville et al., 1947). A recent compendium of tests
has included sixteen single-point tests, and therefore at least this number are likely to be
in current use (RILEM, 2002). Few, if any, of the tests described are suitable for the
complete range of workabilities used in practice. Indeed, many have been developed in
the past two decades in response to the use of increasingly higher workability concrete,
including, most recently, self-compacting concrete.

Four tests have a current British Standard: slump, compacting factor, Vebe and flow
table (or more simply, flow), and will now be discussed together with the slump flow test,
an adaptation of the slump test for self-compacting concrete, and the degree of compactability
test, which has replaced the compacting factor test in the recent European Standards. The
tests are shown and described in Figures 1.1–1.6. Table 1.1 gives the principles on which
they operate, and some comments on their use.

The slump test (Figure 1.1), which is simple, quick and cheap, is almost universally
used for nearly all types of medium and high workability concrete. As well as the drawbacks
listed in Table 1.1, there are also some differences in practice with its use in different
countries, particularly with respect to the British and American standards.

First, the British and European Standards specify that the slump should be measured
to the highest point of the concrete, whereas the American standard specifies measurement
to the displaced original centre of the top surface of the concrete (as shown in Figure 1.1).
Clearly, the same test on the same concrete can give different values depending on where
it is performed.

Second, the British standard only recognizes values from a true slump as valid, and
does not allow recording of values from either shear or collapsed slump (Figure 1.1); the
American standard includes a similar restriction for shear slump, but allows measurements
of a collapsed slump, and values of 250 mm and above are often reported. The recent
European standard states that the test is sensitive to changes in consistency corresponding
to slumps between 10 and 200 mm, and the test is not considered suitable beyond these
extremes.

The flow table (Figure 1.4) test was introduced initially to German standards when
superplasticizers and high workability flowing concrete (i.e. collapsed slump) started to

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