Evaluation of Laboratory Test Used to Assess Rut Potential in the Hot Mix Asphalt and the Effects of Compaction Methods


Book Description

Evaluates various laboratory test methods to assess rutting potential in the hot-mix asphalt (HMA) and the effects of compaction methods. To achieve this objective, rutting potential of HMA samples prepared and compacted in the laboratory, and in the field was evaluated using different laboratory test methods under a range of temperatures and loads.




Evaluation of Warm Mix Asphalt Versus Conventional Hot Mix Asphalt for Field and Laboratory-compacted Specimens


Book Description

A recent joint study by Arizona State University and the Arizona Department of Transportation (ADOT) was conducted to evaluate certain Warm Mix Asphalt (WMA) properties in the laboratory. WMA material was taken from an actual ADOT project that involved two WMA sections. The first section used a foamed-based WMA admixture, and the second section used a chemical-based WMA admixture. The rest of the project included control hot mix asphalt (HMA) mixture. The evaluation included testing of field-core specimens and laboratory compacted specimens. The laboratory specimens were compacted at two different temperatures; 270 °F (132 °C) and 310 °F (154 °C). The experimental plan included four laboratory tests: the dynamic modulus (E*), indirect tensile strength (IDT), moisture damage evaluation using AASHTO T-283 test, and the Hamburg Wheel-track Test. The dynamic modulus E* results of the field cores at 70 °F showed similar E* values for control HMA and foaming-based WMA mixtures; the E* values of the chemical-based WMA mixture were relatively higher. IDT test results of the field cores had comparable finding as the E* results. For the laboratory compacted specimens, both E* and IDT results indicated that decreasing the compaction temperatures from 310 °F to 270 °F did not have any negative effect on the material strength for both WMA mixtures; while the control HMA strength was affected to some extent. It was noticed that E* and IDT results of the chemical-based WMA field cores were high; however, the laboratory compacted specimens results didn't show the same tendency. The moisture sensitivity findings from TSR test disagreed with those of Hamburg test; while TSR results indicated relatively low values of about 60% for all three mixtures, Hamburg test results were quite excellent. In general, the results of this study indicated that both WMA mixes can be best evaluated through field compacted mixes/cores; the results of the laboratory compacted specimens were helpful to a certain extent. The dynamic moduli for the field-core specimens were higher than for those compacted in the laboratory. The moisture damage findings indicated that more investigations are needed to evaluate moisture damage susceptibility in field.




Advances in Interlaboratory Testing and Evaluation of Bituminous Materials


Book Description

This STAR on asphalt materials presents the achievements of RILEM TC 206 ATB, acquired over many years of interlaboratory tests and international knowledge exchange. It covers experimental aspects of bituminous binder fatigue testing; the background on compaction methods and imaging techniques for characterizing asphalt mixtures including validation of a new imaging software; it focuses on experimental questions and analysis tools regarding mechanical wheel tracking tests, comparing results from different labs and using finite element techniques. Furthermore, long-term rutting prediction and evaluation for an Austrian road are discussed, followed by an extensive analysis and test program on interlayer bond testing of three different test sections which were specifically constructed for this purpose. Finally, the key issue of manufacturing reclaimed hot mix asphalt in the laboratory is studied and recommendations for laboratory ageing of bituminous mixtures are given.







Evaluation of Laboratory Conditioning Protocols for Warm-Mix Asphalt


Book Description

Warm-Mix Asphalt (WMA) refers to the asphalt concrete paving material produced and placed at temperatures approximately 50°F lower than those used for Hot-Mix Asphalt (HMA). Economic, environmental and engineering benefits have boosted the use of WMA technology across the world during the past decade. While WMA technology has been successfully utilized as a paving material, several specifications and mix design protocols remain under development. For example, currently, there is no consistent laboratory conditioning procedure for preparing WMA specimens for performance tests, despite being essential for mix performance. Based on previous studies, several candidate conditioning protocols for WMA Laboratory Mixed Laboratory Compacted (LMLC) and off-site Plant Mixed Laboratory Compacted (PMLC) specimens were selected, and their effects on mixture properties were evaluated. Mixture stiffness evaluated in a dry condition using the Resilient Modulus (MR) test (ASTM D-7369) was the main parameter used to select a conditioning protocol to simulate pavement stiffness in its early life. The number of Superpave Gyratory Compactor (SGC) gyrations to get 7±0.5% air voids (AV) was the alternative parameter. Extracted binder stiffness and aggregate orientation of field cores and on-site PMLC specimens were evaluated using the Dynamic Shear Rheometer (DSR) (AASHTO T315) and image analysis techniques, respectively. In addition, mixture stiffness in a wet condition was evaluated using the Hamburg Wheel-Track Test (HWTT) (AASHTO T324) stripping inflection point (SIP) and rutting depth at a certain number of passes. Several conclusions are made based on test results. LMLC specimens conditioned for 2 hours at 240°F (116°C) for WMA and 275°F (135°C) for HMA had similar stiffnesses as cores collected during the early life of field pavements. For off-site PMLC specimens, different conditioning protocols are recommended to simulate stiffnesses of on-site PMLC specimens: reheat to 240°F (116°C) for WMA with additives and reheat to 275°F (135°C) for HMA and foamed WMA. Additionally, binder stiffness, aggregate orientation, and overall AV had significant effects on mixture stiffness. Mixture stiffness results for PMFC cores and on-site PMLC specimens in a wet condition as indicated by HWTT agree with those in a dry condition in MR testing. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/148143




Advances in Interlaboratory Testing and Evaluation of Bituminous Materials


Book Description

This STAR on asphalt materials presents the achievements of RILEM TC 206 ATB, acquired over many years of interlaboratory tests and international knowledge exchange. It covers experimental aspects of bituminous binder fatigue testing; the background on compaction methods and imaging techniques for characterizing asphalt mixtures including validation of a new imaging software; it focuses on experimental questions and analysis tools regarding mechanical wheel tracking tests, comparing results from different labs and using finite element techniques. Furthermore, long-term rutting prediction and evaluation for an Austrian road are discussed, followed by an extensive analysis and test program on interlayer bond testing of three different test sections which were specifically constructed for this purpose. Finally, the key issue of manufacturing reclaimed hot mix asphalt in the laboratory is studied and recommendations for laboratory ageing of bituminous mixtures are given.










Modeling of Hot-mix Asphalt Compaction


Book Description

Compaction is the process of reducing the volume of hot-mix asphalt (HMA) by the application of external forces. As a result of compaction, the volume of air voids decreases, aggregate interlock increases, and interparticle friction increases. The quality of field compaction of HMA is one of the most important elements influencing asphalt pavement performance. Poor compaction has been associated with asphalt bleeding in hot weather, moisture damage, excessive aging and associated cracking, and premature permanent deformation. This study was conducted to develop a model within the context of a thermomechanical framework for the compaction of asphalt mixtures. The asphalt mixture was modeled as a nonlinear compressible material exhibiting time-dependent properties. A numerical scheme based on finite elements was employed to solve the equations governing compaction mechanisms. The material model was implemented in the Computer Aided Pavement Analysis (CAPA-3D) finite-element (FE) package. Due to the difficulty of conducting tests on the mixture at the compaction temperature, a procedure was developed to determine the model's parameters from the analysis of the Superpave® gyratory compaction curves. A number of mixtures were compacted in the Superpave® gyratory compactor using an angle of 1.25 degrees in order to determine the model's parameters. Consequently, the model was used to predict the compaction curves of mixtures compacted using a 2-degree angle of gyration. The model compared reasonably well with the compaction curves. FE simulations of the compaction of several pavement sections were conducted in this study. The results demonstrated the potential of the material model to represent asphalt mixture field compaction. The developed model is a useful tool for simulating the compaction of asphalt mixtures under laboratory and field conditions. In addition, it can be used to determine the influence of various material properties and mixture designs on the model's parameters and mixture compactability.