Effects of chromite ore-processing residue on concrete structures

In the 1960s, a number of industrial and commercial buildings in the Kearny, New Jersey, area were constructed on or adjacent to locally produced chromite ore-processing residue (COPR). This residue, which has the properties of a sandy/silty soil, was used as a fill material to reclaim the indigenous swampy ground conditions, known locally as the "Meadowlands". Generally, the fill stratum is between 4 and 10 ft thick and contains varying amounts of hexavalent and trivalent chromium. It has been alleged that chromium causes damage to structures through various mechanisms. The authors have considered these allegations through research and review of the literature, field investigations of over 100 structures built on or near COPR, field studies involving concrete exposed to COPR, and laboratory studies. The results of the investigations and studies are discussed in this article. It has been found that the existing distress on building and bridge structures is no different from the types and magnitudes of distress seen on other similar structures founded on non-COPR soils. The distress observed was attributable to such things as normal weathering, impact lack of maintenance, improper design or construction, and application of deicer salts. The field experiments for the effects of COPR on concrete have shown no correlation between the level of hexavalent or trivalent chromium and the deterioration of concrete. The single most important factor to the deterioration of concrete was the quality of the concrete mixture. Similarly, the laboratory experiments on corrosion of reinforcing steel in concrete or soil showed no effects of COPR on corrosion.