Date of Award

Winter 2009

Project Type

Thesis

Program or Major

Civil Engineering

Degree Name

Master of Science

First Advisor

Jeffrey Melton

Abstract

In United States, every year approximately 300 million cubic yards of sediments are dredged in order to improve the shipping navigation and deepen the harbors. Out of these dredged sediments, approximately 3--12 million cubic yards sediments are contaminated. Disposal of clean sediments has various possibilities but contaminated sediments require special and expensive treatments.

The current research aims at utilization of mildly contaminated sediments in positive way in order to find better management techniques. Ideally, solidification and stabilization of the sediments would allow them to be used in beneficial use application. Artificial aggregates were prepared using accelerated carbonation technique in which mixture of sediments, water and portland cement was carbonated in 100% carbon dioxide atmosphere. Accelerated carbonation technique facilitated sequestration of carbon dioxide, thereby enhancing the properties of the material. Statistical technique was applied to analyze various artificial aggregate mixtures. In order to determine the key process parameters for process optimization, small scale experiments were performed. The optimum mixture obtained was 55% sediments, 25% portland cement and 20% water. The mixture was carbonated for 2 hours in tumbler to produce artificial aggregates. Full scale experiments were carried out on optimum mixture taking into consideration key process parameters. For the suitability of these artificial aggregates in highway environment different kinds of analyses were performed to ensure solidification and stabilization of contaminated sediments. The characterization of artificial aggregates included particle size analysis, modified Proctor test, California Bearing Ratio test scanning electron microscopy, Thermogravimetric analysis and pH dependent leaching test. Particle size analysis revealed that artificial aggregates were uniformly graded. The CBR value of 40.4 was obtained which was within the range of GW type material. Scanning electron microscopy along with Thermogravimetric analysis suggested that higher percentage of clay in the sediments caused formation of two distinct layers in an aggregate obstructing the uniform formation of CaCO3. The pH dependent leaching test results showed reduction in the release of metals in carbonated artificial aggregates that uncarbonated raw sediments. Finally, it was concluded that artificial carbonation of contaminated sediments can create artificial aggregates and they can be used in beneficial use application.

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