There are over 1.6 million miles of unpaved gravel roads (53% of all roads) in the United States. Increased development, and its associated increases in traffic and vehicle loads, have put significant pressure on local governments to upgrade these roads at considerable expense. There is a strong interest in developing effective, convenient, and economic methods to upgrade these roads. One solution being considered is to stabilize the existing unpaved roadway in situ using self-cementing coal combustion products (CCPs) and then to overlay the stabilized material with hot mix asphalt (HMA). In situ stabilization of the existing material is attractive because the construction can be done rapidly and at low cost. The high strength and stiffness of the stabilized material is expected to provide good support for the HMA and enhance resistance to frost action. Despite these advantages, this high volume application of coal combustion products (CCPs) has received little attention to date. For instance, the FHWA/USEPA publication Fly Ash Facts for Highway Engineers does not list fly ash stabilization of gravel roads for paving purposes as one of its highway applications. Due to the large number of gravel roads awaiting improvement, this application can be expected to have major impact on CCP markets once it is shown to work effectively and a rational design procedure is made available.
The objective of the proposed study is to develop a generalized background and design methodology for in situ stabilization of gravel roads with self-cementing CCPs based on quantitative laboratory and field data. The study would consist of a laboratory experimental program and monitoring of a field demonstration project previously constructed by the PIs. The field project consists of a segment of gravel road (County Road, CR, 53) in Minnesota that was stabilized in situ with fly ash and then overlain with HMA pavement. This roadway will be monitored for two years as part of the proposed study.
The proposed study is divided into five main tasks: (i) collection and characterization of gravel and CCP samples, (ii) stabilization assessment (mechanical tests to define the level of stabilization achieved with CCPs when mixed with gravel, durability tests to evaluate the improvement relative to frost action and to wet-dry cycles, and long-term tests to determine the rate at which stabilization occurs over time), (iii) environmental impact assessment through leach testing and analysis of field leaching data collected from a lysimeter installed at CR 53, (iv) continuing monitoring of CR 53 to quantitatively establish field behavior and durability, and (v) analysis and reporting.
Tuncer Edil
University of Wisconsin
750 University Avenue
Madison, WI 53706
608-262-3225 Telephone
608-262-5199 Fax
edil@engr.wisc.edu