Low-Cost Rural Surface Alternatives: Tech Transfer Summary
Freezing and thawing action induces damage to unbound gravel roads in Iowa resulting in maintenance costs for secondary road departments. Some approaches currently used by County Engineers to deal with this problem include temporarily spreading rock on the affected areas, lowering or improving drainage ditches, tiling, bridging the area with stone and geosynthetic covered by a top course of aggregate or gravel, coring boreholes and filling them with calcium chloride to melt lenses and provide drainage, and re-grading the crown to a slope of 4% to 6% to maximize spring drainage. However, most of these maintenance solutions are aimed at dealing with conditions after they occur. This study was tasked with identifying alternative approaches in the literature to mitigate the problem. An annotated bibliographic record of literature on the topic of frost-heave and thaw-weakening of gravel roads was generated and organized by topic, and all documents were assessed in terms of a suitable rating for mitigating the problem in Iowa. Over 300 technical articles were collected and selected down to about 150 relevant articles for a full assessment. The documents collected have been organized in an electronic database, which can be used as a tool by practitioners to search for information regarding the various repair and mitigation solutions, measurement technologies, and experiences that have been documented by selected domestic and international researchers and practitioners.
Out of the 150+ articles, 71 articles were ranked as highly applicable to conditions in Iowa. The primary mitigation methods identified in this study included chemical and mechanical stabilization; scarification, blending, and recompaction; removal and replacement; separation, and reinforcement; geogrids and cellular confinement; drainage control and capillary barriers, and use of alternative materials. It is recommended that demonstration research projects be established to examine a range of construction methods and materials for treating granular surfaced roadways to mitigate frost-heave and thaw-weakening problems. Preliminary frost-susceptibility test results from ASTM D5916 are included for a range of Iowa materials.
Conducted by the Center for Earthworks Engineering Research (CEER)
See also InTrans Project Reports (http://lib.dr.iastate.edu/intrans_reports/) for the 4-page summary related to this technology transfer summary: Low-Cost Rural Surface Alternatives: Literature Review and Recommendations.
Also known as Iowa Highway Research Board (IHRB) Project TR-632