Retired Racehorses

Laboratory Performance Testing
Composition testing has the distinct limitation that it only describes the material, not the results
which occur from the composition of the material. For surfaces which may have unique local sand or
clay, this is particularly problematic since the performance of the track may not be consistent with other
tracks which have similar composition. As a result, there is a need for both laboratory performance
testing to evaluate the performance of the components of the track material and to determine if the
composition produces values similar to other racing surfaces. In addition the in‐situ performance testing
should be used to describe the overall performance of the material when combined with the design of
the track.
Shear strength
The shear strength of the cushion material is the most fundamental characteristic of the
performance of the track. A material with high cohesion will reduce the slide during the impact phase of
the gait; low shear strength will keep the track from supporting the hoof during the propulsion phase of
the gait resulting in cupping out. Finally, during breakover on many materials the toe of the hoof will
penetrate into the track which is also characterized by the shear strength of the material. Figure 3 shows
the configuration of the test cell used for the shear strength testing which is based on a standard test
method (ASTM D4767, 2004). In the case of traditional materials the testing is done at a range of
moisture contents, whereas the track material temperature is controlled for the synthetic materials.
Figure 3: Configuration of the triaxial test cell used for the determining the triaxial shear strength of
track cushion materials
In the triaxial shear the test is performed using a cylinder of the test material which is
surrounded by a pressurized fluid. The top of the cylindrical test specimen is loaded and the deflection
of the sample is measured. The point at which the sample begins to fail is the shear strength at a
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