Date of Award

Summer 1998

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering - (M.S.)

Department

Civil and Environmental Engineering

First Advisor

Jay N. Meegoda

Second Advisor

Dorairaja Raghu

Third Advisor

David Washington

Abstract

This research investigated the pilot scale feasibility of the remediation of chromium contaminated soil through cold top ex-situ vitrification and the reuse of the vitrified products as highway construction aggregates. There are more than two million tons of chromite ore residues from the chromate extraction manufacturing leftover in Hudson County, New Jersey. They contained both un-leached hexavalent and unoxidized trivalent chromium. Hexavalent chromium is well known as a group A human carcinogen. It is also considered an environmental and health hazard. Of the many ex- situ and in-situ physical, chemical, and biological treatment technologies for chromate production waste, the ability to reduce hexavalent chromium to trivalent chromium and at the same time inhibit the reversal back to hexavalent chromium as well as being able to demonstrate long-term, low toxic metal leaching characteristics is a critical criteria for technology evaluation.

Cold top ex-situ vitrification has been identified to satisfy the above criteria as a highly cost effective and environmentally sound physical treatment. The toxicity characteristic leaching process (TCLP) test results confirmed the effectiveness of the treatment technology. This research describes test results of the use of the vitrified material as aggregate in hot mix asphalt.

The physical properties of vitrified chromium contaminated soils were compared with the New Jersey Department of Transportation (NJDOT) specifications for aggregates to evaluate the reuse potential as a construction material. The crushed vitrified contaminated soils met all the desired NJDOT specifications for aggregates. The inclusion of those aggregates in hot mix asphalt concrete produced NJDOT acceptable mix. The freeze/thaw and wet/dry durability tests and permeability tests produced acceptable values for specimens made from both mixes at optimum asphalt contents. From the test results it can be concluded that the vitrified material can be used in the production of asphalt concrete providing less than 60% vitrified material is included in the mix.

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