13. Type of Report and Period Covered 14. Sponsoring Agency Code 15. Supplementary Notes AbstractThis report investigates the viability of using volcanic ash deposited from the eruption of Mt. Mazama as a natural pozzolan and substitute for the more conventional methods of soil stabilization and unpaved roadway improvement, including dust abatement. Chemical analyses show that Mt. Mazama volcanic ash has similar chemistry to that found in many pozzolanic materials. Standard and modified ASTM strength activity index (SAI) testing was performed on a variety of mixtures containing volcanic ash, hydrated lime, crushed volcanic ash and portland cement at different percentages. A gravel wash sieve test and a slurry mix test were devised in order to determine how the ash could be used to both penetrate into compacted gravel layers and bind material together for the prevention of dust mitigation as defined by the EPA. These new procedures indicate that Mt. Mazama ash can be effective as a supplement to portland cement for binding compacted gravel layers and reducing the dust particulate percentage. Mt. Mazama ash, mixed with highly compressible and organic soil, does not increase unconfined compressive strength. Sustainability studies show that any replacement of portland cement with volcanic ash reduces carbon dioxide emissions and embodied energy.

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