Abstract:
Experimental research was undertaken to exploit the use of an innovative laser
scanning tool and to apply the equipment to the study of (G1) road construction
aggregate obtained from crushed rock quarry sources. The aim of the research was to
better quantify particle shape and surface texture characteristics and an attempt was
made to relate these to the shear strength properties of the materials investigated. By
obtaining a better understanding of the effects that particle shape and texture have on
the shear strength properties of a material, the overall efficiency of construction
aggregate may be improved. Physical material properties and possible effects related
to the (geological) origin of the materials were also considered.
In order to assess the particle data obtained from scan results, models were derived
which could sort individual particles in order, based on their shape and/or surface
texture. These models were created by experimental modelling of physical particle
properties (i.e. dimensions, volume and surface area) obtained from scan results. A
total of 1149 particles scan data were collected. After experimentation, at least two
working concept models were proposed using the scan data, one of which was
ultimately abandoned as the model was affected by the elongation (i.e. shape) of
particles. The second model proved to be better than the first and was further refined
to develop a reference system for each particle size to enable comparison of particle
textures.
After developing the comparative models described above, the aggregate texture
value (ATV) was conceived and refined. A system was developed whereby an
aggregate texture value was derived for the elongated and regular constituents of an
aggregate sample, after separating particle data based on the particles shape. The
aggregate texture value weighed in the average model value calculated based on the
grading analysis of a particular sample as well as the percentage of elongated particles
in a specific size constituent of a sample. The newly developed aggregate texture value was then related to limited tri-axial
shear test results to establish whether there is a correlation between the parameter and
the shear strength properties of the aggregate.
Findings indicate that the models developed and the newly derived aggregate texture
value hold significant potential in better quantifying the shear behaviour of
aggregates. While this research is based on a limited sample size and data, it is
considered a pilot project and the preliminary results justify further, extensive data
accumulation and model refinement.
