The objective of this study is to evaluate the rheological properties and chemical bonding of nano-modified asphalt binders blended with nanosilica In this study, the nanosilica was added to the control asphalt at contents of 4% and 6% based on the weight of asphalt binders Superpave binder and mixture tests were utilized in this study to estimate the characteristics of the nano-modifed asphalt binder and mixture The rotational viscosity (RV), dynamic shear rheometer (DSR), bending beam rhometer (BBR), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), asphalt pavement analyzer (APA), dynamic modulus (DM) and flow number (FN) tests were used to analyze rheological properties and chemical bonding changes of the nano-modified asphalt binder and the performance of the nano-modified asphalt mixture In addition, the performance of nano-modified asphalt after rolling thin-film oven (RTFO) short-term and pressure-aging vessel (PAV) long-term aging was assessed as well

Rheological Properties and Chemical Bonding of Asphalt Modified with Nanosilica

The findings of an extensive literature review on bitumen and asphalt mixture ageing test methods are presented in the paper. The primary factors affecting the durability of bituminous paving mixtures, assuming they are constructed correctly, are age hardening and moisture damage. Ageing of the bituminous binder is manifested as an increase in its stiffness (or viscosity). Water damage is generally manifested as a loss of cohesion in the mixture and/or loss of adhesion between the bitumen and aggregate interface (stripping). Short-term ageing is primarily due to volatilisation of the bitumen within the asphalt mixture during mixing and construction, while long-term ageing is due to oxidation and some steric hardening in the field. Of the tests used to simulate short-term ageing, the extended heating procedures of the thin film oven test (TFOT) and the rolling thin film oven test (RTFOT) are the most frequently used binder methods. In regard to long-term binder ageing, the oxidative pressure ageing vessel ...

State of the Art Report on Ageing Test Methods for Bituminous Pavement Materials

Rutting has been considered the most serious distress in flexible pavements for many years. Flow number is an explanatory index for the evaluation of the rutting potential of asphalt mixtures. In this study, a promising variant of genetic programming, namely, gene expression programming (GEP), is utilized to predict the flow number of dense asphalt-aggregate mixtures. The proposed constitutive models relate the flow number of Marshall specimens to the coarse and fine aggregate contents, percentage of air voids, percentage of voids in mineral aggregate, Marshall stability, and Marshall flow. Different correlations were developed using different combinations of the influencing parameters. The comprehensive experimental database used for the development of the correlations was established on the basis of a series of uniaxial dynamic-creep tests conducted in this study. Relative importance values of various predictor variables were calculated to determine their contributions to the flow number prediction. A multiple-least-squares-regression (MLSR) analysis was performed to benchmark the GEP models. For more verification, a subsequent parametric study was carried out, and the trends of the results were confirmed with the results of previous studies. The results indicate that the proposed correlations are effectively capable of evaluating the flow number of asphalt mixtures. The GEP-based formulas are simple, straightforward, and particularly valuable for providing an analysis tool accessible to practicing engineers.

Nonlinear Genetic-Based Models for Prediction of Flow Number of Asphalt Mixtures

The objective of this study was to characterize hot-mix asphalt (HMA) viscoelastic properties at intermediate and high temperatures and to incorporate laboratory-determined parameters into a three-dimensional finite element (FE) model to accurately simulate pavement responses to vehicular loading at different temperatures and speeds. Results of the developed FE model were compared against field-measured pavement responses from the Virginia Smart Road. Results of this analysis indicated that the elastic theory grossly underpredicts pavement responses to vehicular loading at intermediate and high temperatures. In addition, the elastic FE model could not simulate permanent deformation or delayed recovery, a known characteristic of HMA materials. In contrast, results of the FE viscoelastic model were in better agreement with field measurements. In this case, the average error in the prediction was less than 15%. The FE model successfully simulated retardation of the response in the transverse direction and rapid relaxation of HMA in the longitudinal direction. Moreover, the developed model allowed predicting primary rutting damage at the surface and its partial recovery after load application.

Viscoelastic Modeling and Field Validation of Flexible Pavements

In laboratory testing of asphalt mixtures, the relationship between the number of load repetitions and permanent deformation has been found to include three distinct stages, namely the primary, secondary and tertiary stages. Similar permanent deformation behavior has also been observed in the field accelerated pavement testing data. It is argued that the three-stage permanent deformation behavior is a basic material property and to comprehensively model asphalt layer behavior, it is necessary to develop a model that accurately characterizes this behavior. In this paper, each of the well-known models critically reviewed appears that they are limited to characterizing only the primary stage. Therefore, a new three-stage model is proposed to describe all three stages. Moreover, an algorithm is established to determine the model parameters from typical laboratory data. The algorithm can also be used to identify the transition point between stages, such as flow number. The proposed model and algorithm are demonstrated through laboratory test results. The analysis results match the field performance.

Verification and modeling of three-stage permanent deformation behavior of asphalt mixes

This report presents the findings of a research task to identify a simple test for confirming key performance characteristics of Superpave volumetric mix designs. In this initial phase of the work, candidate tests for permanent deformation, fatigue cracking, and low-temperature cracking were identified and recommended for field validation in the next phase of work. The report will be of particular interest to materials engineers in state highway agencies, as well as to materials suppliers and paving contractor personnel responsible for design and production of hot mix asphalt.

Simple performance test for superpave mix design

This manual presents the procedures for an Asphalt-Aggregate Mixture Analysis System (AAMAS) developed under NCHRP Research Project 9-6(1). The procedures included in the manual are intended to be used for the design and evaluation of dense-graded hot-mixed asphalt concrete mixtures, based on performance-related criteria for high-volume roadways. This manual is the first of three documents, and constitutes the Procedural Manual for mixture design and AAMAS. This manual is divided into four parts. Part I (Selection of Mixture Components) presents the guidelines and criteria recommended for selecting the mixture components, Part II (Mixture Design) is the mixture design procedure, Part III (Mixture Analyses) discusses the test procedures that are required for AAMAS, and Part IV (Mixture Performance Evaluation) discusses the mechanistic-empirical procedures used to predict mixture behavior under traffic and environmental loads.

Asphalt-aggregate mixture analysis system: aamas

This study was conducted as an important subtask work effort within the National Cooperative Highway Research Program (NCHRP). The study objective was to determine, using specimens fabricated in the Superpave Gyratory Compactor, the minimum test specimen dimensions that provide measured responses and material properties that are independent of the test specimen size and aggregate size. The work was carried out in two parallel experiments addressing specimen size and geometry effects in uniaxial compression and constant height shear tests. Both experiments were designed as full factorials using nominal aggregate size, aspect ratio, and diameters the controlled variables and included mixtures with nominal aggregate sizes of 12.5, 19, and 37.5-mm. Several parameters from two tests: complex modulus and repeated load permanent deformation were used to evaluate specimen geometry and aggregate size effects. The complex modulus tests were used to evaluate these effects for low strain responses, while the permanent deformation tests were used to evaluate these effects for large strain measurements. The full factorial experiments were analyzed using analysis of variance to determine the significance of the effects of specimen dimensions on the measured material properties. Additionally, graphical analyses were performed to investigate the rationality of the observed effects and to aid in establishing the limiting specimen dimensions, which the material properties are independent of specimen dimensions. An analysis test variance was conducted for critical parameters. The variability and statistical results were then combined to arrive at minimum recommended sample sizes. For uniaxial compression tests, the study concluded that a sample size of 100-mm in diameter and 150-mm in height is adequate to accurately characterize fundamental dynamic modulus and permanent deformation responses.

Specimen geometry and aggregate size effects in uniaxial compression and constant height shear tests

Major changes in the asphalt pavement industry have occurred in the last 10 years. Potential changes in the next 10 years will be substantial and highly positive to technology. This paper presents an overview of recent research efforts undertaken to recommend a fundamentally based laboratory "Simple Performance Test" (SPT) for permanent deformation evaluation of asphalt mixtures. The test is intended to be used within the newly adopted "Superpave" volumetric mixture design procedure, and to provide accurate correlation to field rutting performance. The laboratory testing program included mixtures and performance data from three major experimental sites: the Minnesota Road Project (MnROAD), the Federal Highway Administration (FHWA) Accelerated Loading Facility Study (ALF), and the FHWA Performance Related Specifications Study (WesTrack). Eleven test types and over eighty test response parameters were evaluated. This paper focuses on three selected candidate tests for the rutting evaluation: the dynamic modulus, static creep, and the repeated load permanent deformation tests.

Pursuit of the simple performance test for asphalt mixture rutting

This report presents a recommended "Guide for Pavement-Type Selection." The guide includes practical, logical, and transparent processes for conducting systematic evaluations of pavement alternatives and for making decisions on pavement-type selection. These processes can be used for both agency-based and contractor-based type selections and may be applied to different pavement types and structures. These processes are supplemented by examples to illustrate the application of the recommended guide for the commonly encountered scenarios of alternative bidding and design-build of operations and maintenance projects. The material contained in the report will be of immediate interest to state pavement engineers, design consultants, paving contractors, and others involved in project design and pavement-type selection.

H L Von Quintus

Papers

Simple performance test for superpave mix design

Asphalt-aggregate mixture analysis system: aamas

Specimen geometry and aggregate size effects in uniaxial compression and constant height shear tests

Pursuit of the simple performance test for asphalt mixture rutting

Guide for Pavement-Type Selection