Date of Award

12-2023

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

Committee Chair/Advisor

Dr. Brad Putman

Committee Member

Dr. Prasad Rao Rangaraju

Committee Member

Dr. Kalyan Piratla

Abstract

Since the 1970s, South Carolina has employed open graded friction courses (OGFC) on high-speed asphalt roadways to enhance wet weather safety. While these mixes have indeed enhanced safety, they still grapple with durability issues, particularly concerning raveling. This research aimed to assess the prolonged performance of OGFC pavements in South Carolina, with a specific emphasis on isolated raveling occurrences. In 2012, the South Carolina Department of Transportation (SCDOT), constructed the first Warm Mix OGFC test section in South Carolina on I-20 Eastbound in Kershaw County, spanning 3.9 miles, using the Evotherm additive and excluding fibers. Following the success of this project, contractors continued to opt for warm mix OGFC in their bids, mostly using the Evotherm additive. After almost 10 years since its first application in 2012, Evotherm has been used in WMA OGFC applications across multiple sections of I-20, I-26, I-385, I-77, I-85, I-95. This led to a need to do a comparative analysis of performance between the previously used HMA OGFC mixes and the WMA OGFC mixes. A comprehensive visual evaluation covered 70 pavement sections, spanning a total of 1,304 lane-miles. Google Earth aided in pinpointing the onset year of each raveling instance. These sections were divided into two groups: 35 HMA sections (434 lane miles) and 35 WMA sections (870 lane miles). The results of this study showed that despite accounting for age differences, hot mix asphalt (HMA) sections displayed increased raveling compared to warm mix asphalt (WMA) 3 counterparts. Raveling instances emerged as early as one year after completion, with an average onset of around six years. Notably, raveling was more pronounced at bridge departures than approaches, with HMA bridges exhibiting a fivefold increase and WMA bridges a threefold rise. Transverse joint locations experienced more frequent raveling than mid-shift sites, a trend that varied between older HMA sections emphasizing mid-shift raveling, and WMA sections following the overall pattern. Additionally, transverse joint raveling was initiated about a year earlier than mid-shift occurrences. These findings provide insights that can help to optimize OGFC surface durability and effectiveness in South Carolina. This study found WMA mixes had lower binder content (0.2% less) and finer gradations than HMA mixes. WMA's lower temperature range (265-285°F) versus HMA (320-350°F) could improve road durability by reducing oxidative aging during production and construction.

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