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Title:Investigation on the mechanisms of block cracking in asphalt pavements
Author(s):Wang, He
Director of Research:Buttlar, William G.
Doctoral Committee Chair(s):Buttlar, William G.
Doctoral Committee Member(s):Tutumluer, Erol; Reis, Henrique; Roesler, Jeff
Department / Program:Civil & Environmental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Block cracking
Asphalt Pavements
Abstract:Block cracking in asphalt pavements is a primary form of surface cracking but has been the subject of very few scientific investigations. The extensive nature of this cracking form often leads to significant maintenance costs and reduces the ride quality and service life of the pavement surface. Although this deterioration mode is covered in many pavement evaluation guides and condition rating systems, the underlying mechanisms of block cracking have not been fully investigated. Therefore, understanding the mechanisms behind block cracking and tailoring preventive solutions merits rigorous investigation. In this thesis, a three-dimensional analytical elastic model of a two-layer pavement system subjected to constant thermal stresses, a two-dimensional discrete element viscoelastic and heterogeneous micromechanical model, and a three-dimensional discrete element viscoelastic and inhomogeneous micromechanical pavement model subjected to thermal straining were developed. Analytical solutions of displacement and stress fields are presented in equation and graphical form, and the use of the model as a tool for block crack size prediction was demonstrated. A typical PG 64-22, dense-graded Illinois asphalt surface mixture was adopted as the baseline material in the discrete element model because it typically experiences block cracking later in its service life. The mechanisms of block cracking patterns were investigated as a function of the dimension of pavement segments, relaxation capacity and aging state of materials, including spatial gradients, cooling rate and pre-existing crack presence using the aforementioned discrete element models. Discrete element simulations showed that both rectangular and hexagonal shaped cracking could occur under the same assumption, with initial block cracking primarily occurring in the upper one-to-two centimeters of the surface which agreed with field observations. In addition, it was found that block cracks formed at warmer temperatures than those associated with the onset of traditional thermal (or transverse) cracking. This implied that current test criteria for thermal cracking mitigation may need to be updated or supplemented in order to control block cracking. Finally, possible candidates for preventive maintenance and tailored maintenance techniques were discussed.
Issue Date:2018-12-03
Rights Information:Copyright 2018 He Wang
Date Available in IDEALS:2019-02-06
Date Deposited:2018-12

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