33
d
&
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MAY-JUNE 2015
AGGREGATE
WASHING
produced.”
“In theUKby contrast, it is joinedup
very intelligently, in fairness. TheAggregates
Levy is creating funds that arebeingput
into recycling, there are schemes such as
Aggregain andWRAP that arewell funded
andwell set up that provide information and
research findings, andmany government
contracts in theUK require theuseof 20%
recycledmaterial. The result is amarket and a
demand for thismaterial.”
Hewent to say that local virginmaterial
cost has amajor impact on the acceptance of
recycled aggregate– if it is high, therewill be
ademand for recycledbut if it is low, there
will be littleor nodemand.
Perhaps theUK aggregates recyclingmodel
is one that other countries could emulate, in
thatwhile often anational governmentmight
wish for increaseduseof recycledmaterial in
new constructionprojects, theremight not
be a framework inplace to in essence force
construction companies touse thatmaterial,
whether it be by taxation, grand aidor other
elements.
SMALL TO LARGE SCALE
Somemight think that the relatively small
throughput ademolition contractormight
expect in a recyclingoperationwhen
compared to virgin aggregateproduction
mightmake it not cost-effective to employ a
washplant. IainWalker certainlybelieves that
this is not the case.He told
D&Ri
that: “The
systems are scaled. Iwould say thatwehave
everything from40 tonnes per hour upwards
anddependingon the typeofmaterial,
that is not necessarilyhigh volume. So for
demolitionwaste applications, itwouldgo
through that veryquickly. Wehave found
that the recyclingmarket inFrance tends to
be for smaller volumes and capacities, in the
40 tonneper hour range, soourAggwash
machine, which is a logwash integrated
with screening and recycling is a really good
solutionbecause it’s a single chassis but quite
a smallmachine, so there is amarket sector
comingup for that.”
Hewent on: “In theUK, the recyclingof
demolitionwaste ismore established andwe
find that typical applications aremore in the
70 to120 tonnes per hour range, and that is
reasonably typical of someotherEuropean
markets. And even further afield, I’vebeen
involvedwith enquiries from countries such
asEgypt andotherMiddleEast states, and
thesehave averaged100 tonnes per hour. The
types of systemweoffer are appropriate for
these volumes.”
He continued: “If you take the larger
‘depot’ approach [transfer station] to
recycling, you can install larger plant in a
fixed installation. The interestingpoint to
this, and especially in theUK, is thatwith
landfill costs growing year on year, it is now
commercially viable to considermaking the
necessary investment in largerwashplant.”
In fact TWSdoes havemachines in it is
range that specifically tuned to the recycling
role. Iain said: “We bundle construction,
demolition and excavationwaste together
whenwe talk about our systems because each
of thesematerials is highly variable soour
systems have tobe able to copewith this. In
our process, we arehandlingmaterial of 100
mm (4 inch) down andbasicallywhat our
higher level
with the largermaterial retained as a ‘good
enough’ low valueproduct. The rejected
material is getting increasingly expensive to
dispensewithplus there is ademand for it
providing it is of sufficient quality.”
“If you take thewashing approach, you can
remove thepaper, plastic andwood, you can
remove the clays, so theproduct youhave at
the endof theprocess ismuch,muchhigher
quality so it fetches abetter price. In addition,
you arenot throwing the -20mmor -10
away, you are capturing that as an additional
product. Iwould estimate that 40% less of the
feedmaterial goes to landfill at the endof the
washingprocess, which is ahuge cost saving.
Theother 60% is the aggregate thatwould
havebeenproduced anyway, but it is ofmuch
higher quality andhence of greater value.”
He continued: “Oneof thebarriers to the
useof recycled aggregate is that often there
is not a joinedup approach. Agovernment
maywant to see a lot of recyclingbut theydo
not do enough to incentivise it or themarket
is not ready touse recycledmaterials. As an
example, inQatar theywanted to recycle
waste, the government found a company
to take on a contract todo it, but in the
end the contractor found that the country’s
building standards said that you couldnot use
recycledmaterial innew construction so it
was impossible for him to sell thematerial he
The first stage in the aggregatewashing process –
pre-screening the feedmaterial to remove fines
Metal in the feedmaterial can be removed by an overbandmagnet, just aswithmobile crushers and screens
