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Feasibility of Gravel Road and Shoulder Recycling

Project Details
STATUS

In-Progress

PROJECT NUMBER

TR-685

START DATE

01/01/15

END DATE

04/30/18

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Jeramy Ashlock

Faculty Affiliate

Co-Principal Investigator
Charles Jahren

Associate Director, Construction Materials and Methods / Asset Management

About the research

Unpaved gravel road surfaces and shoulders frequently experience extensive damage due to degradation of materials under heavy traffic loading and winter/spring freeze-thaw cycles. Additionally, substantial amounts of material are typically lost to whip-off and dusting. The damage results in several problems, including surface deterioration, loss of crown, surface water erosion, rutting, and potholes. Unfortunately, the most unfavorable scenarios usually occur during spring thaws and rainy seasons, when gravel roads are heavily used by planting and harvesting traffic. Current maintenance practice typically involves covering the entire damaged road surface using virgin aggregate without compaction. However, due to the continually increasing price and scarcity of virgin aggregates, this is not the most sustainable and economical solution.

Most previous research on gravel road stabilization has primarily focused on using costly chemical stabilizers or geosynthetics to improve performance and durability. However, the gradation, angularity, and plasticity of surface course, subgrade, and shoulder materials are also important influence factors that evolve with time due to weathering, erosion, and abrasion by traffic loads.

More cost-effective solutions may be realized by focusing on recycling and processing the existing materials to return them to the optimum gradation, angularity, and plasticity index, while minimizing the amount of virgin aggregates required. Recycling of existing materials could also be used in conjunction with chemical and mechanical stabilizers for improved performance where necessary.

This project aims to develop recycling methods to restore the performance of gravel roads by recovering their original gradations and plasticity indexes while reducing the use of virgin aggregate.

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