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The slump test was made-up by Chapman in 1913. Initially he used a cylinder, but because the concrete became fixed in the cylinder, particularly if it was stiff or cohesive, he put a taper on the cylinder and the slump cone has remained the same measurement ever since – 100mm diameter at the top, 200mm diameter at the bottom and 300mm in height.
Amusingly, if the slope angle of the cone is changed the recorded slump will remain the same. This was celebrated by R.V.Watson in 1973 when he did an evaluation of the slump test as his thesis for the Advanced Concrete Technology Examination, an obligation for membership of the Institute of Concrete Technology.
But the slump is more associated to the overall rheological properties of the concrete. For example a concrete with a slump of 100mm made from 20mm crushed rock aggregate will be extra workable than a slump of 100mm in concrete made from crushed rock 10mm aggregate. This is because of particle interlock playing a fraction in the way the concrete slumps and flows when the cone is lifted off the molded concrete. Likewise concrete made with a rounded aggregate will have a better slump for the same mix proportions.
THE ABRAMS SLUMP TEST
The slump test was made-up by Chapman in 1913. Initially he used a cylinder, but because the concrete became fixed in the cylinder, particularly if it was stiff or cohesive, he put a taper on the cylinder and the slump cone has remained the same measurement ever since – 100mm diameter at the top, 200mm diameter at the bottom and 300mm in height.
Amusingly, if the slope angle of the cone is changed the recorded slump will remain the same. This was celebrated by R.V.Watson in 1973 when he did an evaluation of the slump test as his thesis for the Advanced Concrete Technology Examination, an obligation for membership of the Institute of Concrete Technology.
Watson did slump tests on especially made cones with a different slope angle as part of his evaluation of the test. Soon after its invention it was popularized by Duff Abrams in 1917 and in some text it is referred to as the ‘Abram’s Cone’ although it is called a workability test the slump is really a measure of the consistence of the concrete. If batches of the same concrete are produced with nominally the same or similar values of slump, the concrete can be said to be consistent, in that the batches are containing an approximately identical amount and proportion of ingredients per cubic meter. Ultimately the slump is a measure of workability because the higher the slump the easier the concrete is to place and compact.
But the slump is more associated to the overall rheological properties of the concrete. For example a concrete with a slump of 100mm made from 20mm crushed rock aggregate will be extra workable than a slump of 100mm in concrete made from crushed rock 10mm aggregate. This is because of particle interlock playing a fraction in the way the concrete slumps and flows when the cone is lifted off the molded concrete. Likewise concrete made with a rounded aggregate will have a better slump for the same mix proportions.
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