Date of Award

8-2013

Degree Name

Master of Science

Department

Geosciences

First Advisor

Dr. Daniel Cassidy

Second Advisor

Dr. Duane Hampton

Third Advisor

Dr. David Barnes

Access Setting

Masters Thesis-Open Access

Abstract

Powdered activated carbon (PAC) is often added with cement to enhance the stabilization and solidification (S/S) of materials contaminated with organic compounds. Adsorption of organic contaminants onto PAC can reduce leaching of organic contaminants. Simultaneous addition of PAC and cement reduces soil handling costs, but cement hydration reactions coat PAC with Ca(OH)2 before contaminants can be adsorbed onto PAC. Laboratory studies were done on four aged, contaminated soils from manufactured gas plant sites to compare the performance of S/S treatment with simultaneous addition of PAC and cement vs. cement addition after preconditioning with PAC to enhance contaminant adsorption. Performance was evaluated by quantifying the leaching of BTEX and naphthalene with the synthetic precipitation leaching procedure, and by measuring unconfined compressive strength in amended soil samples. Ordinary (Type I) Portland cement, quicklime, and Class C fly ash were the cementing agents tested. A period of 15 to 25 weeks was required for a 1% PAC amendment to optimally reduce contaminant leaching. Adding cement after a 20-week PAC preconditioning time dramatically enhanced leaching and strength compared with adding cement and PAC simultaneously. The results from this work suggest that PAC is only effective when allowed sufficient preconditioning time before cement addition.

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