Date of Graduation

1-2016

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering (MSCE)

Degree Level

Graduate

Department

Civil Engineering

Advisor

Andrew F. Braham

Committee Member

Kevin D. Hall

Second Committee Member

Ernest Heymsfield

Keywords

Social sciences; Applied sciences; Asphalt; Pavement; Poisson's ratio; Transportation

Abstract

Poisson´s ratio can be defined as the negative ratio of strains perpendicular to the load direction to the strains parallel to the loading direction. If elastic or viscoelastic models are used, Poisson´s ratio, together with elastic modulus, is a main input used to predict distresses in flexible pavement structures such as rutting and cracking. In asphalt concrete, Poisson’s ratio is commonly measured using two different testing configurations: indirect tension (IDT) and uniaxial. However, results from these two testing configuration can potentially have differences. Design methodologies such as the Mechanistic Empirical Design Guide (MEPDG, now PavementME) have been shown to be very sensitive to variations of Poisson’s ratio. The objective of this research is to determine whether or not there are significant differences between the values of Poisson’s ratio measured in indirect tension configuration and uniaxial configuration. This work also aims to investigate the potential variations of values of Poisson’s ratio among a number of asphalt mixture treated with different types of asphalt modifiers: poplyphosphoric acid (PPA) alone and in combination with liquid anti-stripping agent (LAA). Cylindrical shaped samples specified in AASHTO T 342 were used to measure Poisson’s ratio in uniaxial configuration, and disc shaped samples specified in AASHTO T 322 were used to measure Poisson’s ratio in an IDT configuration. Samples were tested at each combination at the following temperatures, -10 C, 4 C, 21 C, 37 C, and 54 C, and frequencies, 25 Hz, 10 Hz, 5 Hz, 1 Hz, 0.5 Hz, and 0.1 Hz. No statistical difference was found in values of Poisson’s ratio measured within each testing configuration. IDT Poisson’s ratio were significantly different to those of uniaxial configuration (3:1). This reduction of Poisson’s ratio by about 60% could lead to an increment of predicted distresses, such as longitudinal cracking, using PavementME by more than 400% of its design limit.

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