Publication Date

5-2023

Date of Final Oral Examination (Defense)

March 2023

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Civil Engineering

Department

Civil Engineering

Major Advisor

Yang Lu, Ph.D.

Advisor

Nick Hudyma, Ph.D.

Advisor

Dave Zhai, Ph.D., industry expert

Advisor

Alex Rosales, M.S., industry expert

Abstract

Interest in sustainable practices have increased in several industries, including civil engineering pavement materials. The incorporation of Recycled Asphalt Pavement (RAP) into new pavement mix design is a popular method of application for sustainable practice and is accompanied by numerous economic and environmental benefits. There is significant interest in using large amounts of this RAP material in pavement design to maximize the benefits, but several problems arise when utilizing “high” amounts of this material (more than 25% RAP replacement) due to aged and oxidized binder that negatively impacts the properties. The use of rejuvenators (RAs) and Balanced Mix Design (BMD) are some solutions that are used to minimize negative impact on overall mix properties. RAs are added to high RAP-inclusive mixes to revitalize the RAP binder properties to allow for the best mix characteristics. BMD has quickly gained traction and popularity over the Superpave mix design method, as BMD considers the interaction effects of recycled materials and additives while also balancing performance testing results and designing pavement to a specific area condition. The application of sustainable practices such as high RAP mix design must result in a pavement that fulfills its purpose, and service life, and does not suffer from premature failure in the field for it to be worthwhile. Continuous research in this area of interest is crucial for the future of pavement materials.

This research project aims to provide a methodical approach to high RAP mix design that can be applied to pavement design for future works. It also works to evaluate the performance of two RAs in RAP mixes at 25%, 50%, and 70% RAP replacement. The performance tests assess the rutting and cracking resistance with the goal of balancing these two so both perform adequately well. Additionally, two different RA doses are compared for RA1 (bio-based). A simple cost savings analysis is reviewed for the mix options per ton. Finally, a brief exploration of the chemical analysis comparison for different binder blends provides some insight into the different performance test results. The results of this research indicate a successful process of high RAP mix design and promising savings for the use of RAP in HMA mix design. The bio-based RA (RA1) performed the best overall of the two RAs, and the dose selection contrast of results reinforces that the initial method of RA dose selection is promising.

DOI

https://doi.org/10.18122/td.2071.boisestate

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