MPC
Research Projects (2006-07)

Identifying Number

MPC-274

Project Title

Beneficial Use of Waste Tire Rubber in Low-Volume Road and Bridge Construction, Year 1

University

Colorado State University

Project Investigator:

Dr. J. Antonio Carraro, CSU
carraro@colostate.edu

External Project Contact

N/A

Project Objective

The main objectives of this project are: (1) to evaluate the geotechnical properties of expansive soil-rubber (ESR) mixtures required for the mechanistic design of low-volume road embankments and bridge abutments, (2) to design a typical low-volume road embankment cross-section using a computer model, (3) to construct a pilot road section and monitor its performance to demonstrate the feasibility of the proposed technology, and (4) to disseminate the project findings through the publication of technical papers and by holding a one-day workshop involving state, county, and city engineers as well as students and professionals interested in the technology.

Project Abstract

Untreated native soil with high swell potential has been identified as one of the major contributing factors in the development of premature longitudinal cracking and other pavement distresses in Colorado (Ardani et al, 2003). Unique regional factors such as a semi-arid climate and widely-occurring expansive soil deposits have made cost-effective maintenance and rehabilitation of bridges and pavements a challenging task in the region. Although excessive movement of pavement and bridge structures has been reported in both rural and urban areas in Colorado, this issue represents a particular burden for local governments due to the higher costs typically associated with the construction, maintenance, and rehabilitation of low-volume roads and bridges founded on expansive soils. Increasing costs of conventional (e.g. gravel, sand) and alternative (e.g. fly ash) road construction materials and heavier truck and farm equipment loads have only added up to the problem.

While waste tires and waste tire rubber have been used in many engineering applications such as highway embankments and retaining wall backfills, most of these previous works have dealt with rubber-sand mixtures (e.g. Lee et al., 1999). Among the few studies that have focused on rubber-clay mixtures (e.g. Ahmed and Lovel, 1993; Edil and Bosscher, 1994; Tatlisoz et al 1997), none of them have investigated the effect of rubber on the engineering properties of highly-expansive clays such as the ones found in rural and urban areas of Colorado. In this study, we will address the beneficial use of waste tire rubber on the swelling potential mitigation of local expansive soils and characterize the mechanical response of ESR mixtures through a systematic experimental investigation. The adequacy of ESR mixtures as an alternative road construction material will be evaluated through computational modeling of sections of highway embankments designed with these mixtures. Pilot field-scale road section(s) will be constructed and monitored with the assistance of public transportation agencies, counties and local municipalities in Northern Colorado. It is hypothesized that the improved properties of properly designed and compacted ESR mixtures will reduce the overall costs associated with the construction, maintenance, and rehabilitation of low-volume roads in the region.

Task Descriptions

1. Literature review. Comprehensive review of the literature on the project's topic: compilation of a source availability map for all waste tire rubber suppliers in Colorado and their proximity to major expansive soil deposits.
2. Laboratory testing. Sample collection, physical characterization (grain-size distribution, specific gravity, plastic and liquid limits) of the materials tested; mixture design and determination of the standard (ASTM D698) and modified (ASTM D1557) compaction parameters, swelling percent and pressure, unconfined compressive and tensile strengths of the ESR mixtures; consolidation and triaxial testing (at effective confining stress levels typically encountered in road embankments) to determine the consolidation, shear strength, and small-strained parameters of the ESR mixtures.
3. Mechanistic pavement design. A computer program will be used to design typical cross-sections of low-volume road pavements based on the mechanical properties and parameters determined in task 2. ESR pavement sections that present reasonable engineering properties and adequate mechanical response (i.e. tolerable compression strain in the sub-grade, tolerable tensile strain in the surface layer, and acceptable swell percent), and maximize the beneficial use of waste tire rubber will be considered for the demonstration activities described next.
4. Construction of pilot pavement sections: Full-scale pavement test sections containing mechanistically-designed base, and/or sub-base, and/or sub-grade made of ESR mixtures, will be constructed by external partners with supplementary financial assistance provided by the Colorado Waste Tire Program (CDOLA, 2006), which is administered by the Colorado Department of Local Affairs (CDOLA).
5. Monitoring of the pilot pavement section. Full-scale pavement sections constructed by the project partners will be monitored to quantify distresses typically observed in pavements constructed on expansive soils. The "Distress Identification Manual for the Long-Term Pavement Performance Project - SHRP-P-338" (NRC, 1993), will provide the basic guidelines for this task.
6. Cost benefit analysis. Evaluate the economic and environmental adequacy of the proposed technology. Relevant factors that will help assess both economic and environmental benefits imparted by the proposed technology include determination of the amount of waste tire rubber recycled per unit volume of pavement, costs associated with the landfill space freed due to the adoption of the proposed technology, and construction and maintenance costs for the pilot sections.
7. Report writing. Write up of the interim and comprehensive final technical reports.
8. Technology transfer. A one-day workshop will be held at the end of the project at Colorado State University to disseminate the findings among state, county and city engineers, and other local geotechnical and transportation engineering professionals and students interested in the proposed technology.

Milestones, Dates

Starting Date: July 1, 2006
Ending Date: June 30, 2007

Yearly and Total Budget

$84,946

Student Involvement

One graduate student

Relationship to Other Research Projects

N/A

Technology Transfer Activities

The project outcomes will be presented and discussed during a one-day workshop. The target workshop audience will be comprised of state, county and city engineers, and local geotechnical and transportation engineering professionals and students. A set of two TLN 1-2 hour videoconferences will be given by the graduate student to provide practical information on the experimental research findings to practicing state, county and city engineers and students from other MPC universities.

Potential Benefits of the Project

The products of the project will comprise (1) mentoring of a qualified graduate student; (2) publication of a graduate thesis and peer-reviewed journal paper(s); (3) written MPC interim report; and (4) written MPC final technical report. The construction of full-scale test section(s) will allow close collaboration with local county and city engineers and establishment of a long-term partnership with local governments.

TRB Keywords

Low Volume Roads and Bridges, Waste Tires, Rubber, Expansive Soil, Recycling