Date of Award

12-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Civil Engineering

Committee Member

Bradley J. Putman, Committee Chair

Committee Member

Amirreza Esmaeilpoursaee

Committee Member

Nadarajah Ravichandran

Abstract

Understanding how the aggregate structure changes during mixing andcompacting are critical for the performance of open graded asphalt designs. Open gradedfriction course (OGFC) consists of approximately 94% aggregate and if breakdownoccurs, the desired properties of the finished product will vary. The purpose of this studywas to investigate the influence of the Los Angeles (LA) abrasion value of the aggregateon the performance of open graded friction course mixtures. Aggregate from nine different sources in South Carolina, with LA abrasion valuesranging from low-20s to mid-50s, were used to create a 12.5mm nominal maximumaggregate size (NMAS) open graded design. Specimens, both with and without theinclusion of binder, were mixed then compacted using a Superpave gyratory compactorand re-analyzed for gradation change. Durability performance was measured using theCantabro abrasion test while functional performance was measured by porosity. Substantial degradation was exhibited after both mixing and compacting foraggregates having higher LA values. All aggregate sources sustained breakdown,especially in the #4, #8 and #30 sized fractions. The inclusion of binder increased theaggregate breakdown rate more so than the aggregate mixtures tested without binder.Higher LA aggregate exhibited a decrease in specimen height and porosity whileimproving the Cantabro abrasion resistance. The aggregate source used in open-graded mixtures will affect the functional anddurability performance of the finished pavement. Under current specifications, there are many opportunities for variability between paving projects using aggregate from different sources. Degradation from mixing and compacting can be predicted if the aggregate behavior is known, therefore, appropriate corrections should be made to OGFC gradations to account for this breakdown of aggregate and enhance the pavement quality.

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