A Veeraragavan

According to the definition of the American Association of State Highway and Transportation Officials (AASHTO), a Pavement Management System (PMS) is a set of tools or methods that assist decisionmakers in finding optimum strategies for providing, evaluating and maintaining pavements in a serviceable condition over a period of time. The purpose of pavement management systems is to help in making cost-effective decisions related to pavements. It has been shown that, implementing properly designed and developed PMS depends mainly on three factors: Reliable data, realistic models for processing the data and user-friendly software for organizing the inputs and presenting the outputs. This paper presents the development of pavement performance prediction models for the selected arterial and sub-Arterial roads in Tiruchirappalli city of Tamil Nadu, India. Road inventory data, pavement condition data and roughness data of the study area were collected periodically during pre monsoon and post monsoon seasons for five years from 2010 to 2015. The Pavement Condition Index is calculated for the road sections. A quadratic regression model is developed to represent the pavement deterioration characteristics and various maintenance activities have been identified for treatment. The Optimization model was developed using the GAMS (Generic Algebraic Modeling System) software after formulating the objective function and the constraints.

The performance of a pavement depends on factors like the characteristics of the materials in different pavement layers, traffic, climates, environments, construction quality, etc. Though a pavement is designed for 15 years, conventionally, the pavement reaches the threshold level of performance before the design life, warranting minor and major rehabilitation treatments because of factors beyond the control of the designer. However, the maintenance and rehabilitation treatments during the design life of a pavement are not considered in the design process. The performance of a pavement is defined in terms of the various distresses, i.e., cracking, rutting, roughness, potholes, etc. The performance of the pavement also depends on the strength properties of different pavement layers and their thicknesses, quality of construction, traffic, climate, etc. The level of influence of these parameters on each of the distresses is different. In this study, the Mechanistic Empirical Pavement Design Guideline design tool AASHTOWare is used to simulate the data for cracking (percentage of bottom up fatigue cracking), rutting (total rutting), and roughness in terms of the International Roughness Index. A sensitivity analysis is carried out to study the influence of the design parameters on the distresses. From the results of AASHTOWare simulations, a relationship is established between design input parameters and distress growth using multiple linear regression. While this model gives the estimate of distress over time with respect to the design parameters, the year at which the first preservation activity has to be carried out is to be determined. Considering the pavement as a system, the system dynamics concept could be well suited to study the influence of various factors on the performance of the pavement. A system dynamic model is formulated and implemented using system dynamic software POWERSIM. This study identifies the optimal intervention year for the pavement preservation strategies that depend on traffic level, design layer thicknesses, and modulus (strength) of the pavement layers.

This paper presents the results of investigations on the rheological properties of modified asphalt binders and their influence on the performance of asphalt mixes. Asphalt mixes with modified binders such as styrene butadiene styrene polymer, crumb rubber, natural rubber, and waste plastics were evaluated for their rheological properties and compared to the properties of asphalt mixes with unmodified VG30 (viscosity grade) asphalt binder. The dynamic modulus values and rutting characteristics of the asphalt mixes were studied with due consideration to different levels of aging and temperature variations. Studies on the rheological properties showed that the energy dissipated by unmodified asphalt (VG30) binder is higher than that of modified asphalt binders. Long-term aged natural rubber and waste plastic modified asphalt binders showed significant increase in the properties compared to unmodified asphalt binder (VG30). Reduced temperature susceptibility of polymer modified asphalt binder showed that only polymer modification can enhance both high temperature rutting resistance and low temperature thermal cracking resistance of asphalt mixes. The transient nature of polymer modified asphalt mix from viscoelastic solid-like to viscoelastic fluid-like condition is significantly shifted to higher temperature compared to that of the mix with unmodified asphalt binder. Aging and rutting indices showed that rubber modified asphalt mixes are highly susceptible to aging. Statistical analysis of test results showed that the process of modification of asphalt binder, aging, and temperature during the test influence the rheological and rutting characteristics of asphalt mixes significantly. Correlation between the asphalt binder properties and its influence on the rutting resistance are found to be statistically significant. The analysis using least significant difference showed that polymer modified asphalt binder significantly improves the aging and rutting resistance of asphalt mixes compared to unmodified asphalt binder. Copyright © 2012 by ASTM International.

In this work, pavement cross-section as stipulated by the Indian Roads Congress code of practice for pavement design was used in the stress-analysis. Typically, two types of asphalt layers are laid over three to four layers of granular materials for pavements constructed for heavy traffic volume in India. Asphalt mixtures pertaining to these top two layers were fabricated with polymer modified and unmodified asphalts in the laboratory. These mixes were tested in the simple performance test equipment at temperature of 60°C under a wide range of frequencies. A four parameter Burgers' model was used for fitting the experimental data for both the asphalt layers. A two-dimensional finite element model of the pavement structure was used within the ABAQUS computing environment. The granular base, subbase and subgrade granular layers were assumed to be elastic. The pavement model was subjected to cycles of periodic loading and the stresses and strains were monitored at all the critical locations. This was used to quantify the influence of modifiers on the mechanical response of the pavement and parametric analysis was carried out to find out enhanced service life of the asphalt layers that could be achieved due to the use of high-performance materials. © 2011 ASCE.

A laboratory investigation was conducted to capture the influence of confinement pressure and specimen air voids on the creep and recovery response of asphalt concrete (AC) mixtures. AC specimens were fabricated at 2% and 7% air voids and tested at three temperatures (20, 40 and 55°C) and at unconfined and confined conditions (100 and 200 kPa). A total of 20,000 repetitions of a repeated trapezoidal loading and recovery cycle were applied. The resulting creep curves showed four distinct patterns of the three-stage creep curve depending on the loading condition and specimen density. To quantify the mechanical response during the secondary stage where the response was found to be linear, linear viscoelastic modelling was carried out. Using creep time, energy stored and energy dissipated, which were determined from model parameters; the influence of air voids and confinement pressure was quantified.

The rationale behind an asphalt mix design is optimizing the binder content for the desired aggregate gradation to satisfy the specified volumetric and strength requirements. The designed asphalt mix should be durable and cost effective. The mechanical behavior of a designed asphalt mix is affected by the traffic loading and climatic variations. To improve the mechanical properties of asphalt mixes, additives are added to the base asphalt binder. These binders are called modified asphalt binders. The objectives of the present study are to compare the performance of asphalt mixes with different binders by two different mix design methods and to optimize the asphalt binder type to achieve the desired performance. Two methods of mix design namely, Marshall and Superpave mix design methods are considered. The performances of asphalt mixes viz., tensile strength, moisture damage, densification and rutting resistance were compared. The results indicated a statistically significant difference in the optimum asphalt binder content from the two mix design methods. The Marshall method of asphalt mix design is found to yield lower optimal asphalt binder content when compared to the Superpave method of mix design. The moisture susceptibility and construction densification index of asphalt mixes designed using Superpave method were found to be significantly lower than that of the mixes designed by Marshall method. Optimization using a Mixed Integer Linear Program (MILP) indicated that the polymer modified asphalt binder outperforms the requirements of engineering properties when compared to other commercial binders used in the study. © 2010 Elsevier Ltd. All rights reserved.

Cold in-place recycling technology for reclaimed material in pavement rehabilitation holds promise as a solution to resource scarcity. This paper reports results of a systematic experimental investigation of the material produced by this technique and in particular the role of cement and air void content. The internal structure is characterized using computed tomography and environmental scanning electron microscopy. A tension and tension-compression test is carried out to characterize the response of the material at 15 and 45°C. From microscopy, it is seen that the addition of cement did not result in formation of hydration compounds, but instead aids in densifying the material substantially. From the mechanical experiments, it is seen that the response of the material is clearly viscoelastic at the temperatures at which it is tested. The experimental data are used to find relevant linear viscoelastic parameters, and a methodology to compute these parameters directly is presented.

The pavement maintenance is a critical component of the pavement life cycle. The effective pavement maintenance needs the pavement performance under do-nothing scenario as well as under various treatment choices. The performance of a pavement is characterized in terms of the various distresses viz., functional distress and structural distress. When a pavement is intervened for maintenance, each treatment offer varied levels of effectiveness for different distresses. These are expressed in deterioration models and treatment effectiveness models. As pavement behaves as a system, the system dynamics concept can be adopted to study the interaction of deterioration progression and treatment effectiveness on traffic loading over a period of time. Integrating the above components with the agency cost, a system dynamic model is formulated and implemented using system dynamic software POWERSIM. Optimization is performed using evolutionary principle in the software. This study identifies the minimum agency cost required for optimal scheduling of pavement maintenance for a planning period of 9 years.

Sensitivity analyses are important parts of both studying complex systems and measuring the variation in input parameters on the response. They are useful to decision makers for understanding the robustness of the optimal solution that they are to adapt to variations of the parameters of the problem. The sensitivity of the optimal solution of a project-level pavement management problem is analyzed, and the robustness of the optimal solution to the interventions and the timing, cost, and benefit are investigated. The input parameters, which affect the optimal maintenance solution, are identified as the structural and functional condition parameters (defined in terms of deflection and roughness, respectively, at the beginning of the analysis period), traffic volume, growth rate, and discount rate. The problem of computing the optimal treatment and timing for a given budget level is modeled as a mixed integer nonlinear optimization problem and solved by using a computationally efficient network-optimization technique. The benefits are evaluated by considering the pavement performance and are quantified as the area between the performance curve and the threshold values. The optimal budget required for pavements in different structural and functional conditions as well as traffic levels is presented. The effect of initial pavement condition on the optimal maintenance actions as well as their timings is studied. The result of the sensitivity analysis showed that the cumulative standard axle loads and traffic growth rate have a significant effect on the selection and timing of rehabilitation and preventive maintenance actions. The effect of the discount rate on the maintenance management decisions is also presented.

Proper assessment of flooded pavement is very critical for reducing the risk and ensuring the safety of construction crews, department of transportation personnel and the public. The objective of this paper is to present a rational procedure for the assessment of vulnerability of asphalt pavements to flood-induced damage. A system dynamics-based methodology was developed to determine the critical time (Tcritical) for full saturation of the unbound base and for failure of the bound surface layer. The methodology and the web-based simulation tool presented here will help the users to identify potentially vulnerable stretches of highway prior to flooding and either take action to improve them or monitor them closely to obtain preflood conditions which can be compared against post-flood conditions to detect deterioration; it will help them decide whether emergency and non-emergency vehicles can be allowed during and immediately after flooding, and in planning post-flooding investigative actions.