Reuse of industrial aggregates is still hindered by concern for their long-term properties.
This paper proposes a laboratory method for accelerated ageing of steel slag, to predict
environmental and technical properties, starting from fresh slag. Ageing processes
in a 10-year old asphalt road with steel slag of electric arc furnace (EAF) type in
the subbase were identified by scanning electron microscopy (SEM) and leaching tests.
Samples from the road centre and the pavement edge were compared with each other and
with samples of fresh slag. It was found that slag from the pavement edge showed traces
of carbonation and leaching processes, whereas the road centre material was nearly
identical to fresh slag, in spite of an accessible particle structure. Batches of
moisturized road centre material exposed to oxygen, nitrogen or carbon dioxide (CO2)
were used for accelerated ageing. Time (7-14 days), temperature (20-40 degrees C)
and initial slag moisture content (8-20%) were varied to achieve the carbonation (decrease
in pH) and leaching that was observed in the pavement edge material. After ageing,
water was added to assess leaching of metals and macroelements. 12% moisture, CO2
and seven days at 40 degrees C gave the lowest pH value. This also reproduced the
observed ageing effect for Ca, Cu, Ba, Fe, Mn, Pb, Ca (decreased leaching) and for
V, Si, and Al (increased leaching). However, ageing effects on SO4, DOC and Cr were
not reproduced.