BENEFICIATION
MIX DESIGN PROCESS
GETS FACELIFT
Much Asphalt uses Afrisam’s Rooikraal quarry, near Vosloorus, for about 95% of the
aggregate required at its Benoni flagship plant.
By Eamonn Ryan
An important redesign process is currently underway regarding asphalt mix design for road
building. Industry-driven, it aims to help roads withstand potentially hotter climatic conditions for
greater durability.
U
ntil flying cars become
ubiquitous, asphalt roads will be
here to stay and even then we’ll
need parking lots. Asphalt manufacturing
uses an average 5% of the total aggregate
produced on quarries, but it’s a
disproportionately vital 5% that affects our
everyday lives.
30_QUARRY SA| JANUARY/FEBRUARY 2019
In a Forrest Gump aphorism, ‘making
asphalt is like baking a cake’, you measure
all the right ingredients, mix them up and
heat it to get the final product. Asphalt
starts with a mixture of aggregate, then
bitumen is heated and combined with
stones and dust. Each one of these steps
is a science in itself, because raw material
standards are exacting. After all, these are
high-volume roads being made and the
pavement material must be kept pliable for
proper installation. Asphalt facilities must
therefore be located near paving sites.
Aggregate comprises about 95% of
the raw material of asphalt, and the
asphalt market is normally four to five