CICEET Progress Report for the period 9/01/01 through 3/01/02

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.

As reported in the last progress report, the tasks scheduled for this reporting period were as follows:

• Investigate heavy metal (As, Cu, Cd, Cr, Pb, Hg, and Zn) leaching characteristics of the various forms of dredged material (DM) produced (raw slurry containing DM, DM portland cement clinker, as well as the DM itself and concrete product from DM-cement clinker) using pH-static testing. These tests are conducted using an automatic titrator that keeps a certain sediment sample at a constant pH for a given amount of time. Knowing how contaminant concentrations vary with pH will lead to a better understanding of the phases and availability of the contaminants.
• Use acid digestion procedures to approximate the total contaminant content of each material previously mentioned. The gathered information will be combined with the leaching results to support assessments of human and environmental risks.
• Manufacture portland cement clinker with varying proportions of DM (0%, 1.5%, 6.63%, and 12.5%) at bench-scale in laboratory.
• Use x-ray powder diffraction (XRPD) to evaluate the quality of the clinkers manufactured with varying percentages of DM and look at the major clinker phases present, as well as any unusual ones that may affect the performance of the portland cement.
• Investigate the impact of the high chloride concentration of the DM. This will be done through discussions with experts from cement plants, literature reviews, and experiments in the lab.

Progress on Tasks
The graduate students working on this project, Jennifer Dalton and Mindy Weimer, continue to review literature sources relevant to this topic within their respective areas of study. As a structural/materials student in civil engineering, Jennifer has been focusing on the manufacture of Portland cement, particularly at the laboratory-scale, and the use of waste and alternative materials in this manufacturing process. Meanwhile, Mindy, an environmental engineering student, has been concentrating on literature sources related to the fate of contaminants Î particularly those typically found in dredged sediments Î during high temperature processes such cement manufacture.

The pH-static test data to this point has been compiled (see "Preliminary Data") and more data continues to be collected to improve the accuracy of these results. Total contaminant concentrations have been determined via acid digestion procedures, to assess a material mass balance and ultimately quantify volatilization. Evaluation of contaminant phases using XPS is at hand and will confirm conclusions from pH-static work.

Raw feed slurries containing varying amounts of DM (0%, 1.5%, 6.63%, and 12.5%) were proportioned, measured, blended, and then ground in a ceramic ball mill in the laboratory. These slurries were then used to manufacture small amounts of portland cement clinker with a muffle furnace in the laboratory at the bench scale. The clinkers produced were ground again in a ball mill and analyzed with XRPD (see results in "Preliminary Data").

The high chloride concentration of the DM, and subsequently the raw slurry and clinker produced with the DM has been investigated. This has been done through literature review and discussions with "experts" from cement plants, as well experiments in the lab. To date it has become apparent that high chloride contents are mostly a problem with the cement manufacturing process as the chlorides volatilize during the heating process and cause problems with scaling in the kiln and pollution control devices. As a result there is no definite chloride limit in the cement slurry; it is more a function of the manufacturing facility's components as well as the process used- wet or dry. Mixing ammonium nitrate into the raw mix to complex with the chlorides and cause them to volatilize at lower temperatures was investigated. The presence of the ammonium nitrate did not appear to result in volatilization of chloride at 400°C as expected. Results from this investigation are reported in Section E "Preliminary Data".

Dissemination Activities
Jennifer presented this work in an oral presentation at the Recycled Material Resource Center's "Beneficial Use of Recycled Materials in Transportation Applications," held in Washington D.C. November 13-15, 2001. Bryan Magee also gave a presentation at the International Conference on Remediation of Contaminated Sediments in Venice, Italy on October 10-12, 2001. Mindy will present at the "Third Specialty Conference on Dredging and Dredged Material Disposal" conference in Orlando, FL, May 5-8, 2002. Three manuscripts were also produced:

Weimer, M., J. Dalton, K.H. Gardner, B.J. Magee, "Beneficial Use of Contaminated Materials in Portland Cement Manufacture for Sustainable Resource Management," Environmental Engineering and Policy (Submitted 9/01).

Dalton, J., M. Weimer, K.H. Gardner, B.J. Magee, "Engineering Aspects Governing the Beneficial Use of Dredged Materials in Cement Manufacturing," In Beneficial Use of Recycled Materials in Transportation Applications, T.T.Eighmy Eds., Air and Waste Management Association Press (In Press).

Gardner, K.H., B.J. Magee, M. Weimer, J. Dalton, "Beneficial Use of Dredged Materials in Portland Cement Manufacture," International Conference on Remediation of Contaminated Sediments, Venice, Italy, October, 2001.

Difficulties Encountered
None.

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 Results
Research continues on Portland cement mixes manufactured at the laboratory scale using a muffle furnace. To analyze the cement manufactured with 6.63% NY/NJ sediment, the NY/NJ sediment itself, as well as ordinary Portland cement, extraction Method 3050B (using repeated additions of HNO₃ and H₂O₂), analyzed by Method 6010B, was followed. The results are considered to represent the maximum environmentally available contaminant levels. The data thus far was used to show the effect of manufacturing cement with dredged material by comparing cement mixed with 6.63% dredged material (i.e. the dredged material was not heated in the latter experiment but just mixed with cement). This comparison shows a reduction of the environmental availability of contaminants after manufacturing dredged material and other raw materials into cement (see Figure 1).

Further studies of contaminant availability are underway by means of pH-static testing. Clinker mixes as well as slurry mixes have been tested; Figures 2-4 show initial clinker results. It is not surprising that at extreme pH conditions yield the highest contaminant availability. Cadmium availability, as shown in Figure 2, appears not to change significantly with pH changes. Figure 3 shows lead availability increases in the high pH range when clinker is made with dredged material. Leaching of zinc from the clinker mixes (Figure 4) all follow a similar pattern aside from the outlier. More data collection is in progress to improve the confidence of contaminant availability conclusions.

To quantify the amount of trace heavy metal contaminants volatilized through manufacturing Portland cement, extraction Method 3050B analyzed by Method 6010B was again followed. 3g samples of each: dredged material (DMA), control slurry, control clinker, high clinker (12%), medium clinker (6.5%), and low clinker (1.5%), were analyzed by Resource Laboratories in Portsmouth, NH, to find total contaminant concentrations, shown in Table 1.

Using the DMA and Slurry Control values, different slurry mixtures were proportioned as follows:

0.015 * DMA + 0.985 * Slurry Control = Low Slurry

This calculation example was followed for each element, and for both the Medium and High Slurry mixes (see Table 2) Volatilization was calculated by subtracting predicted total contaminant concentration (Table 1) from measured total concentrations in the clinker (Table 2). This assumes that if we start with the amount in the slurry and end with the amount in the clinker, the remainder volatilized. Table 3 shows the results of these volatilized quantifications. The Control reported in Table 3 represents the Control Slurry and Control Clinker analysis.

The negative values represent an increase in contamination as opposed to the expected decrease due to volatilization. It is important to keep in mind some possible sources of errors:

• Heterogeneity of the dredged material.
• Small sample size.
• Clinkers were cooked with lids.
• Slight disproportionality of the raw mix materials.

To insure clinker quality, X-ray powder diffraction (XRPD) analysis was conducted. A plot of XRPD scans of the clinker samples manufactured with varying amounts of dredged material compared to the control is shown in Figure 5. The XRPD patterns suggest that there are no significant differences in cement composition as a result of the addition of dredged material into the manufacturing process. The minimal variations do not follow a pattern and are more likely due to normal fluctuations in clinker formation.

Results of the NH₄NO₃ experiment are reported in Figure 6. The chloride concentration of the samples after heating to 400°C are shown on the y-axis with the corresponding molar ratio of NH₄NO₃:Cl^- on the x-axis. After seeing that the presence of NH₄NO₃ appeared to have no affect on the volatilization of the chloride in the slurry after heating the samples to 400°C, it was decided to heat the samples to higher temperatures. Figure 7 shows the chloride concentrations in the "A" (control) and "E" batches of slurry after heating the samples to 400, 600, 800, and 1000°C. This plot shows that the chloride does decrease after the slurry is heated to higher and higher temperatures as expected, with the exception of a slight increase between 800 and 1000°C. Both slurry batches show similar chloride concentrations which further reinforces the observation made after the first phase of this experiment: the presence of NH₄NO₃ has no affect on the temperature at which the free chloride volatilizes. The sample from slurry batch E heated to 1000°C does show a slight decrease in free chloride concentration compared to the control, but this is likely not significant.

Tasks and activities for next reporting period

Tasks for the next reporting period
The tasks scheduled for the next (and final) reporting period of this research project are as follows:

• Continue pH-static leaching investigation;
• Begin study of contaminant phases that control the availability of contaminants from DM-clinker and DM-concrete material.
• Finalize XRPD results to allow for more distinct conclusions on clinkers manufactured in the muffle furnace with varying percentages of DM.
• Manufacture portland cement clinker containing 11.25%DM at pilot-scale using a rotary kiln. This process more closely resembles the full scale manufacture and will be done through a subcontract to Construction Technology Laboratory (CTL) in Skokie, IL (the research arm of the Portland Cement Association).
• Use ASTM tests to evaluate the soundness of the cement produced (including compressive strength and setting time). These tests have not been possible until now due to the small amounts of clinker produced in the muffle furnace.

Work plan to accomplish tasks
Refer to details of the tasks mentioned above.

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.