Ainalem Nega

Simulation of Shakedown Behavior in Pavement's Granular Layer

While in the design of flexible pavement the significance of asphalt layers is understood, the role of granular layers supporting the asphalt layers should not be underestimated. The behavior of granular layers used in base, sub-base or subgrade layer of flexible pavement is complicated due to nonlinear elastoplastic response of materials subjected to dynamic load of traffic. Shakedown theory integrated with Mohr-Coulomb criterion is applied to simulate the response of granular layers to dynamic loading in a numerical analysis. The results of analysis is then compared to simple the results of modeling without considering shakedown effects and the conclusion is drawn.

Simulation of Shakedown Behavior for Flexible Pavement’s Unbound Granular Layer

Full-depth asphalt concrete pavements are generally designed to control fatigue cracking and reduce potential rutting when subjected to repeated heavy traffic loads. A particularly interesting question is whether a limit load exists below which excitation shakedown in the sense that the granular layer does not accumulate further deformation. Although pavement design guides give more weight to asphalt concrete layer failures, granular failure may not be ignored; especially for thin layers and/or heavy load. The behavior of granular layers used in base and, subbase layers of flexible pavement is complicated due to its nonlinear elastoplastic response when subjected to dynamic traffic loading. The objective of this paper is to present a new simplified simulation model for the shakedown behavior of granular layer in flexible pavement. This method is integrated with Mohr-Coulomb criterion, which is used and applied to simulate the response of unbound granular layers to dynamic loading in a numerical analysis. The results of analysis are then compared to simplify the results of modeling without considering shakedown effects and then, the conclusions are drawn.

Evaluation and validation of characterization methods for fatigue performance of asphalt mixes for Western Australia

The determination of appropriate pavement thickness using laboratory determined parameters is one of the key issues facing the road manager. Five different types of asphalt mixes were produced in laboratory to modify pavement performance mixture. The main objective of this study is to evaluate the characterization methods for fatigue performance of asphalt mixes to Western Australia road. In this study, laboratory test for indirect tensile modulus, dynamic creep, wheel tracking and aggregate gradation tests were taken to analyze each asphalt mixtures for a design traffic road. The results and analysis showed that AC20-75 asphalt mix blow is the most effective and efficient in pavement performance than the other asphalt mixes. AC14-75 was the second in rank to strengthen and durability of asphalt pavement. All asphalt mixes in this study can be used to strength and stable the overall stiffness of pavement, and modification rank can be described as AC20-75 Blow > AC14-75 Blow > AC14-50 Blow > AC7-50 Blow > SMA7-50 Blow in this research.

Developing Master Curves, Binder Viscosity and Predicting Dynamic Modulus of Polymer-Modified Asphalt Mixtures

The complex moduli relationship related mixture moduli to temperature and time rate of loading has been an integral part of several mechanistic-empirical (M-E) design procedures used throughout of the world. Seven asphalt concrete mixtures of different types of polymer modified binders (PMB) were produced in a laboratory to modify performance of asphalt mixture. The main role of this research is to evaluate the influence of these polymer modifiers on the pavement performance of asphalt mixture with the dynamic modulus, |E*| of hot-mix asphalt (HMA) mixture indicator in a laboratory test for Mainroad Western Australia and Fulton Hogan. In this study, the influence of temperature, loading frequency, and confining pressure on the dynamic characteristic of asphalt mixture were analysis, master curves of dynamic modulus of HMA mixtures were developed and datas were interpreted. Results showed that AC10 5.7% A35P (EVA) M7 B5, AC10 5.7% C450 M10 B5 and AC10 Multi 600/700 M5 B4 mixes method were the more efficient and effective in all categories of asphalt performance measures for strength and durability of HMA as compared to others polymer modifiers. A very good correlation (R 2 = 1) was found for each polymer modifier. This suggested that laboratory test using a various temperatures and loading frequencies can improve pavement mix design, lab and field control and assurance. A strong correlation between binder viscosity and temperature (R 2 = 1) for polymer modified asphalt mixture.

Distress Identification, Cost Analysis and Pavement Temperature Prediction for the Long-Term Pavement Performance for Western Australia

Collection and analysis of pavement distress data is a significant component for effective long-term pavement performance. Accurate, consistent, and repeatable pavement distress types evaluation can reduce a tremendous amount of time and money that has been spending each year on maintenance and rehabilitation of existing pavement distress. The main objective of this study is to identify and quantify of surface distress in a given segment of pavement, to perform details distress rating, to predict pavement temperature and cost analysis of individual pavement distress on heavily urban roads in Western Australia (WA). Field survey were conducted from three regions in WA and two approached were used to evaluate and analysis the pavement distress. First, the probabilistic network Marov-Chain Process method was used to predict the cost analysis for individual asphalt concrete surfaced pavement distress. Second, Statistical Downscaling Model (SDSM) was used to predict pavement temperature for asphalt concrete surface pavement. Meteorological data were collected from Perth, Kalgoorlie, and Albany region in WA, and data were used to develop and validation of the model. Different types of pavement distress level were identified and color photograph illustrated the asphalt concrete surfaced pavement. Results were performed and analysis. Results from this study will be useful resource to Main Roads Western Australia, Western Australia State Highways (WASH), and other pavement related users including to the National Highway System (NHS). In addition, results can be used for pavement management systems (PMSs) purpose.

Engineering Characterization of Hot-Mix Asphalt in Western Australia

The use of full depth asphalt pavement to construct and rehabilitate heavily loaded urban roads that has grown rapidly in Western Australia over the past 3 years. Five different types of asphalt mixes were produced in the laboratory according to the Australian Standard methods of sampling and testing asphalt to modify payment performance mixture. The main role of this research is to evaluate and assess the hotmix asphalt pavement performance characteristic for Western Australia road. In this study, laboratory test for tensile strength, resilient modulus, wheel tracking, asphalt binder content and Marshall Compaction test were taken and analyzed to each asphalt mixtures. Results showed that AC20-75 and AC14-75 Blow asphalt mixes were more efficient and effective in pavement performance as compared to the other mixes. In general, all the asphalt mixes that are used in this study can strength and stable the mixture stiffness of asphalt that is notable. The modification effect rank can be described as AC20-75 Blow > AC14-75 Blow > AC14-50 Blow > AC7-50 Blow > SMA7-50 Blow in this research.

Pavement Materials Characterization of Hot-Mix Asphalt Mixes in Western Australia

The use of deep strength asphalt materials characterization to construct and restore the heavily urban roads where damage has been induced is rapidly grown in Western Australia. Five different types of asphalt mixes were produced in laboratory to modify pavement performance mixture. The main role of this research is to evaluate the pavement materials characterization for Western Australia road. In this study, laboratory test for tensile strength, resilient modulus, wheel tracking, binder contents, Marshall Compaction, and air voids contents test were taken to analyze each asphalt mixtures. The results indicated that AC20-75 and AC14-75 asphalt mixes blow were in a good pavement performance as compared to other asphalt mixes. For a mix design purposed, all the asphalt mixes that are used in this study can strength and stable the stiffness of pavement that is notable, and the modification effect rank can be described as AC20-75 Blow > AC14-75 Blow > AC14-50 Blow > AC7-50 Blow > SMA7-50 Blow in this research.

A comparison between effects of linear and non-linear mechanistic behaviour of materials on the layered flexible pavement response

Modelling granular pavement materials has a significant role in the pavement design procedure. Modelling can be through an experimental or numerical approach to predict the granular behaviour during cyclic loading. The current design process in Australia is based on linear elastic analysis of layers. The analysis is performed through a well-known program CIRCLY which is applied to model bound pavement material behaviour. The KENLAYER is one of the common pavement software models used for pavement design in the United States which performs non-linear analysis for granular materials. Alternatively, a general Finite Element program such as ABAQUS can be used to model the complicated behaviour of multilayer granular materials. This study is to compare results of numerical modelling with these three programs on two sample pavement models.

A comparison between austroads pavement structural design and AASHTO design in flexible pavement

This study deals with the Austroads (2008) Guide to Pavement Technology Part 2: Pavement Structural Design on which most road pavement designs in Australia are based. Flexible pavement designs and performance predictions for pavements containing one of more bound layers derived from the mechanistic Austroads pavement design methodology and the AASHTO-2004 approach are compared for Australian conditions, with consideration of subgrade and other material properties and local design preferences. The comparison has been made through two well-known programs namely CIRCLY (5.0) and KENLAYER. The study shows that each guide has its own advantages and disadvantages in predicting stress and strain in pavement layers under different conditions. The study recommends that modifications are necessary resulting in more realistic and longer lasting pavements in Australia.