© 2006 by Taylor & Francis Group, LLC

96 Corrosion Control Through Organic Coatings
by the fact that, as the chromium concentration in the blasting debris
increased, the TCLP chromium concentration also increased.
• The authors noted that the sequential acid leaching found in their testing
was much more harsh than concrete is likely to experience in the field;
however, it does hint that stabilization of toxic metals with portland
cement will work only as long as the concrete has not broken down.
5.4.3 PROBLEMS WITH ALUMINUM IN CONCRETE
Not all metals can be treated with portland cement alone; aluminum in particular can
be a problem. Khosla and Leming [31] investigated treatment of spent abrasive containing
both lead and aluminum by portland cement. They found that aluminum particles
corroded rapidly in the moist, alkaline environment of the concrete, forming hydrogen
gas. The gas caused the concrete to expand and become porous, decreasing both its
strength and durability. No feasible rapid-set (to avoid expansion) or slow-set (to allow
for corrosion of the aluminum while the concrete was still plastic) was found in this
study. (Interestingly, the amount of lead leaching was below the EPA limit despite the
poor strength of the concrete.) However, Berke and colleagues [32] found that calcium
nitrate was effective at delaying and reducing the corrosion of aluminum in concrete.
5.4.4 TRIALS WITH PORTLAND CEMENT STABILIZATION
In Finland, an on-site trial has been conducted of stabilization of blasting debris
with portland cement. The Koria railroad bridge, approximately 100 m long and 125
years old, was blasted with quartz sand. The initial amount of debris was 150 tons.
This debris was run through a negative-pressure cyclone and then sieved to separate
the debris into four classes. The amount of ‘‘problem debris” — defined in this pilot
project as debris containing more than 60 mg of water-soluble heavy metals per
kilogram debris —remaining after the separation processes was only 2.5 tons. This
was incorporated into the concrete for bottom plates at the local disposal facility [33].
The U.S. Navy has investigated ways to reduce slag abrasive disposal costs in
shipyards and found two methods that are both economically and technically feasible:
reusing the abrasive and stabilizing spent abrasive in concrete. In this investigation,
copper slag abrasive picked up a significant amount of organic contamination (paint
residue), making it unsuitable for portland cement concrete, for which strength is a
requirement. It was noted, however, that the contaminated abrasive would be suitable
in asphalt concrete [34].
5.5 OTHER FILLER USES
Blasting debris can also be incorporated as filler into asphalt and bricks. Very little
is reported in the literature about these uses, in particular which chemical forms the
heavy metals take, how much leaching occurs, and how permanent the whole
arrangement is. In Norway, one company, Per Vestergaard Handelsselkab, has
reported sales of spent blasting media for filler in asphalt since 1992 and for filler
© 2006 by Taylor & Francis Group, LLC