CICEET Progress Report for the period 8/01/02 through 2/01/03

Project Title: Development of Beneficial Use Alternatives for the Management of Dredged, Contaminated Sediments
Principal Investigator(s): Kevin H. Gardner

Accomplishments
Scheduled Tasks:
The long term goal of this project is to investigate the feasibility of the beneficially use of contaminated dredged sediments as partial feedstock materials to manufacture portland cement.

The scheduled tasks for this research project are almost complete. Jennifer Dalton, one of the two graduate students working on the project, successfully defended her Master’s thesis in August, 2002. The environmental studies on the manufactured materials are continuing presently, and will conclude in May, 2003. It is expected that the second student working on the project will complete her Master’s degree by this time. The scheduled tasks were :

• Complete X-ray photoelectron spectroscopic studies of metal-doped clinkers to provide direct evidence of phase distribution of heavy metals in clinkers and concrete materials.
• Complete pH-dependence leaching tests on concretes produced using clinkers manufactured with dredged materials.
• Conduct geochemical modeling of leaching process to gauge ecological or human health impacts from use of dredged materials.
• Prepare Final Report.

Progress on Tasks
The above tasks are all complete except for the geochemical modeling work (70% complete) and the final report.

Dissemination Activities
Gardner, K.H., M. Weimer, J. Dalton, J.C.M. Spear, "Beneficial Use of Dredged Material as an Ingredient in Cement Manufacturing," Emerging Technologies, Tools, and Techniques To Manage Our Coasts in the 21st Century, EPA Technology Transfer Conference, Cocoa Beach, FL, January 27-31, 2003.

Gardner, K.H., M. Weimer, J. Dalton, "Beneficial Use of Contaminated Dredged Material in Conventional Portland Cement Manufacture," The Society of American Military Engineers: Sediment Decontamination and Its Role in an Overall Dredged Material/ Contaminated Sediment Management Strategy, Newark, NJ November 21, 2002.

Seager, T.P., K.H. Gardner, "Development of a Multicriteria Assessment Framework for Management of Contaminated Sediments," 5th International Symposium on Sediment Quality Assessment, Chicago, Illinois, October 16-18, 2002.

Difficulties Encountered
The XPS work did not end up providing any useable information for this research. The primary problem was the detection limit of the instrument. Clinker samples were prepared with 1% by mass of various heavy metal contaminants (Pb, Cd, Cr, etc.) , however, even at these extreme concentrations, which compromise the quality of the clinker produced, solid-phase elemental speciation could not be determined.

Anticipated Success in Meeting Project Objectives in Scheduled Project Period
It is anticipated that the project objectives will be met in the scheduled project period.

Preliminary data
The focus of the research the past six months has been to characterize the environmental behavior of the cement and cement products produced using dredged material. There are a number of issues that were a concern to us and a number of different materials that have been investigated. To characterize any occupational health risks, it was important to understand the leaching behavior of the clinker being produced. Long-term environmental risks also needed to be characterized by studying the leachability from the hydrated material (i.e. the material state when made into concrete). The final materials evaluated were spiked, that is, contaminants were added to the materials so they would be present in much higher concentrations. This was done to facilitate direct observation of speciation in the solid phase material using spectroscopic techniques, which aren’t able to analyze the very low levels present in the material without spiking.

Figure 1 shows the results from a pH-dependent leaching test. These tests have been used extensively in this work to characterize leachability over the entire range of likely environmental pH values and also give an indication of what solid phase precipitates control the availability of the contaminants. Figure 1 demonstrates the effect that hydration of the sample has on lead (Pb) availability by comparing Pb leaching in clinker to Pb leaching from hydrated paste (cement in the glue in concrete, and sets when it becomes hydrated by addition of water). In the neutral pH range, the clinker and paste materials have similar behavior, but at the highest pH (12), the clinker is notably releasing a greater amount of Pb. Pb typically will show this behavior (increase in availability at high pH), so it is expected with the clinker but the fact that Pb leaching does not increase in the paste is noteworthy, suggesting it may be contained within a phase formed during the hydration process.

Figure 2 compares spiked and hydrated material to hydrated material that is not spiked. In order to be truly useful, the spiked material should behave similarly to the other materials so that any phases identified spectroscopically could be assumed to have relevance to the materials with lower contaminant levels. Figure 2 demonstrates the materials do not behave in a similar manner except in the pH 8 to 10 range where Pb is at its minimum solubility. Figure 3 depicts a similar situation with the clinker (not hydrated) samples. The control clinker material and the "medium clinker" (produced using 6.5% dredged material) show very similar lead leaching across the pH range, with some deviation at the highest pH. The spiked material, once again, shows greater availability at lower and higher pH values than the 8-10 minimum solubility range.

Figure 4 contains X-ray diffraction spectra for the control clinker and two spiked clinker materials. From these spectra, various possible Pb phases have been identified, which are given in Table 1. This information is being used in the final phase of this part of the research which is to conduct equilibrium speciation modeling of contaminant availability (all of these graphs and tables also exist for a suite of heavy metal contaminants). If we are able to identify the existence of solid phase materials, the leaching behavior, and can model these results numerically, we can have an excellent indication of the environmental behavior of these cement and concrete materials. This is true not only for the cement product and the concrete produced, but also for the long-term leaching of, for example, the second and third lives of a recycled concrete product.

Tasks and activities for next reporting period

Tasks for the next reporting period
The final tasks to complete are:

• Geochemical modeling of leaching process to gauge ecological or human health impacts from use of dredged materials.
• Final Report preparation and submission.

Concerns or Difficulties
No potential concerns or difficulties are predicted at this time.

Expenditures
Expenditures at this time are in the range anticipated for the work accomplished to date.