Before the inception of this research, a number of methods existed for testing these properties.
These had been developed to assess the key properties of SCC before it is placed, to ensure
that the fresh concrete will indeed be ‘self-compactable’ and will also, when hardened,
achieve the required uniformity in engineering properties. Much more is demanded of SCC in
its fresh state than of conventional vibrated concrete – SCC, though it has to have flowing
characteristics, is not the same as conventional super-plasticised concrete – and it is therefore
more important to verify its properties. Often, the existing tests had been developed in
commercial secrecy for specific applications, and there had been no attempt to ensure that
they were more generally applicable. These tests were largely in the public domain, but
because of the circumstances in which they were developed there was no agreement on which
was the most suitable for general purposes, and there was certainly no immediate prospect,
anywhere, of a standardised test. This hindered the increased use of SCC since it was difficult
to validate mix designs except by full-scale trials (feasible in special projects only), and
confidence in the material was undermined. Establishment of a standardised test, therefore,
was considered an essential prerequisite to realising the potential benefits of SCC and to
facilitating its widespread use in general construction.
The consortium believed that Europe had the opportunity to establish a world-wide lead, since
no country had yet agreed this necessary standard – even Japan, where SCC was first
developed, did not then have any national standards for SCC testing. There, the Institutes of
Civil Engineers and Architects and the Ready-Mixed Concrete Association had different
recommendations on test methods – exactly the situation that this research was intended to
by-pass in Europe. Similarly, in North America there were no co-ordinated proposals for
standardisation. Canada had been more active in research than the USA but, even there, work
had proceeded in individual institutions, not on a national basis.
The tests that had been devised include slump flow, the L-box, the V-funnel, the U-test, the
Orimet, the ‘static sieving’ test, and the J-Ring. In addition some researchers had used
rheometers of different types to make a more fundamental investigation of SCC behaviour.
These tests were considered unsatisfactory for a number of reasons:
• Individually, these tests look at one or two of the three key properties, but none is capable
of assessing all three, nor was there any agreement on which combination of tests might
best be used.
• In particular, none of them was adequate for assessing resistance to segregation.
• Because of the non-standardisation of these methods, there had been large variations in
the ways these tests had been used; there was no consensus on the materials from which
the sets of apparatus have been constructed or on their dimensions. For instance, some of
the tests attempted to reproduce the flow of concrete between reinforcement bars, and
include such bars in their design, but different researchers had used quite different bar
widths and spacing.
• Where concrete in a test was required to flow through a piece of apparatus, the ‘wall
effect’, the constraint on flow imposed by the containing surfaces, had a significant effect
on the results. This effect is dependent on the size of the apparatus, but, again, different
researchers had used different dimensions, so that results could not be compared or
reproduced. Even if the dimensions were the same, the use of a smooth material like steel
or plastic produced different flow characteristics from the use of rougher plywood.
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