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Title:Mechanistic characterization of thin asphalt overlays for pavement preservation
Author(s):Dhasmana, Heena
Director of Research:Al-Qadi, Imad L
Doctoral Committee Chair(s):Al-Qadi, Imad L
Doctoral Committee Member(s):Tutumluer, Erol; Lambros, John; Sehitoglu, Huseyin; Ozer, Hasan
Department / Program:Civil & Environmental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Thin Overlays
Pavement Preservation
Pavement Maintenance
Flexible Pavements
FEM Modeling
Abstract:Thin asphalt concrete (AC) overlays are generally used as a preservation treatment for rigid and flexible pavements to improve ride quality, extend service life, and reduce noise levels on pavements. However, compared to the conventional methods of mechanistic analysis, analyzing thin AC overlay is complicated as these layers are directly exposed to vehicular loading and environmental stimulations. The gradients of material properties resulting from aging and moisture damage, in addition to mix heterogeneity and complex microstructure, violate some of the basic assumptions of pavement evaluation used to date. The proposed research work aims to estimate the performance of thin AC overlays using a mechanistic approach addressing some of the existing complexities. Three-dimensional (3D) finite element (FE) simulations are developed, taking into account features such as vehicular loading, different layer thickness of the thin AC overlay, variation in material parameters, existing pavement condition, underlying layer condition, and temperature changes. Changes in the behavior of critical response parameters in the pavement structure give an idea about the characteristic features of the AC mixes used and the properties of layers when subjected to external loads. Asphalt concrete mix domains near the surface are analyzed to determine the impact of vehicular traffic on the durability of the mix used in thin overlay layers. As expected, higher compression in the thin overlay was observed which gradually changed to a tensile behavior. For the thinnest overlay, high vertical strains were observed at the top of the subgrade layer. For all the responses evaluated, it was noticed that with an increase in the thickness of thin overlay, magnitude of the strains decreased. It was concluded from this analysis that overlay thickness is the principal factor affecting the performance of thin AC overlays. In contrast to a fixed path analysis, domain analysis is an appropriate technique to quantify overlay damage. A study of subdomains created in the pavement layers proved that the zone nearest to the surface had higher compressive as well as shear strains. In addition, the bottom of the AC layer showed relatively high shear and tensile strains. A comparison with a pavement with no thin AC overlay showed that the overlaid pavement had lower compressive strains and lesser value of the average shear strains. With an increase in thickness of the thin overlay, a decrease in compressive and shear strains in the near surface region was observed. Majority of the AC layer displayed higher shear strains with increasing overlay thickness. For the region lying at the bottom of the subdomain, a decrease in the magnitude of pavement responses was recorded. When the existing condition of the pavement was considered, an increase in shear strains within the AC layer was noticed. In general, thin overlays may not contribute significantly to enhancing the structural performance of the pavement because of insufficient bulk strength. Hence, when thin overlay is used as a maintenance option, the pavement structure should be calculated carefully, considering traffic and environmental factors. A model was presented to calculate thin overlay service life.
Issue Date:2020-01-24
Type:Thesis
URI:http://hdl.handle.net/2142/108082
Rights Information:Copyright 2020 Heena Dhasmana
Date Available in IDEALS:2020-08-26
Date Deposited:2020-05


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