Browsing by Subject "Asphalt mixtures"

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Asphalt Mixture and Binder Fracture Testing for 2008 MnROAD Construction
(Minnesota Department of Transportation, 2009-12) Marasteanu, Mihai; Moon, Ki Hoon; Turos, Mugurel
This report summarizes the results of an experimental effort to characterize the low-temperature behavior of asphalt mixtures and binders from the recently reconstructed cells at the MnROAD facility. In depth analysis of the data was not part of this study; this will be accomplished in several concurrent research projects.
Determination of Optimum Time for the Application of Surface Treatments to Asphalt Concrete Pavements - Phase II
(Minnesota Department of Transportation, 2008-06) Marasteanu, Mihai; Velasquez, Raul; Herb, William; Tweet, John; Turos, Mugur; Watson, Mark; Stefan, Heinz G.
Significant resources can be saved if reactive type of maintenance activities are replaced by proactive activities that could significantly extend the pavements service lives. Due to the complexity and the multitude of factors affecting the pavement deterioration process, the current guidelines for applying various maintenance treatments are based on empirical observations of the pavement surface condition with time. This report presents the results of a comprehensive research effort to identify the optimum timing of surface treatment applications by providing a better understanding of the fundamental mechanisms that control the deterioration process of asphalt pavements. Both traditional and nontraditional pavement material characterization methods were carried out. The nontraditional methods consisted of X-Ray Photoelectron Spectroscopy (XPS) for quantifying aging, while for microcracks detection, electron microprobe imaging test (SEM) and fluorescent dyes for inspection of cracking were investigated. A new promising area, the spectral analysis of asphalt pavements to determine aging, was also presented. Traditional methods, such as Bending Beam Rheometer (BBR), Direct Tension (DTT), Dynamic Shear Rheometer (DSR) and Fourier Transform Infrared Spectroscopy (FTIR) for asphalt binders and BBR and Semi-Circular Bending (SCB) for mixtures were used to determine the properties of the field samples studied in this effort. In addition, a substantial analysis of measured pavement temperature data from MnROAD and simulations of pavement temperature using a one-dimensional finite difference heat transfer model were performed.
Disc shaped compact tension (DCT) specifications development for asphalt pavement
(Minnesota Department of Transportation., 2019-06) Dave, Eshan V; Oshone, Mirkat; Schokker, Andrea; Bennett, Chelsea E
The disc-shaped compact tension (DCT) fracture energy test has been shown to discriminate between asphalt mixtures with respect to their thermal cracking potential. This research refines the DCT fracture energy testing procedure, identifies needed adjustments in asphalt mixture to increase fracture energy, determines the suitability of DCT-test-based parameters as indicators of reflective cracking, and proposes threshold values to lower the potential for premature reflective cracking in asphalt overlays. A number of recommendations have been developed to implement outcomes of this research as well as to fill knowledge gaps identified through this study.
The Effect of Voids in Mineral Aggregate (VMA) on Hot-Mix Asphalt Pavements
(Minnesota Department of Transportation, 1999-09) Chadbourn, Bruce A.; Skok, Eugene L. Jr.; Newcomb, David E.; Crow, Benita L.; Spindle, Samantha
This research project investigates the level of Voids in the Mineral Aggregate (VMA) in Minnesota paving projects. Researchers analyzed 10 paving projects from 1996 to determine if a VMA decrease occurred, the magnitude of the decrease, and the potential causes of the decrease. Potential causes include the generation of fines, high-production temperatures, and long storage or cure times. Three of the 10 projects had a VMA decrease of 1.9 or more. These three projects also had the highest plant temperatures and fairly long storage times, which makes increased asphalt absorption a likely cause of the VMA decrease. Five projects showed a moderate drop in VMA. Most had some increases in fines, and some had moderately high plant temperatures and storage times. The two projects with little or no changes in VMA had very little change in gradation, and moderate to low plant temperatures and storage times.
Experimental and Computational Investigations of High-Density Asphalt Mixtures
(Minnesota Department of Transportation, 2019-10) Marasteanu, Mihai; Le, Jia-Liang; Hill, Kimberly; Yan, Tianhao; Man, Teng; Turos, Mugurel; Barman, Manik; Arepalli, Uma Maheswar; Munch, Jared
Compaction of asphalt mixtures represents a critical step in the construction process that significantly affects the performance and durability of asphalt pavements. In this research effort, the compaction process of asphalt mixtures was investigated using a combined experimental and computational approach. The primary goal was to understand the main factors responsible for achieving good density and was triggered by the success of a recently proposed Superpave 5 mix design method. First, a two-scale discrete element method (DEM) model was developed to simulate the compaction process of asphalt mixtures. The computational model was anchored by a fluid dynamics-discrete element model, which is capable of capturing the motion of aggregates in the viscous binder. The model was then calibrated and validated by a series of experiments, which included rheological tests of the binder and a compaction test of the mixture. It was concluded that the compaction process was significantly influenced by the rheological properties of the fine aggregate matrix and by the sphericity of the coarse aggregates. Finally, the mechanical properties of two high-density mixtures were determined and compared with mechanical properties of mixtures used for MnROAD 2017 National road Research Alliance (NRRA) test sections. It was found that the properties of high-density mixtures as a group were not significantly different compared to the properties of conventional mixtures.
Impact of Low Asphalt Binder for Coarse HMA Mixes
(Minnesota Department of Transportation, 2017-06) Dave, Eshan V.; DeCarlo, Christopher; Hoplin, Chelsea M.; Helmer, Benjamin; Dailey, Jay; Williams, R. Christopher
Asphalt mixtures are commonly specified using volumetric controls in combination with aggregate gradation limits, like most transportation agencies, MnDOT also uses this approach. Since 2010 onward, several asphalt paving projects for MnDOT have been constructed using coarser asphalt mixtures that are manufactured with lower total asphalt binder contents. Due to the severe cold climate conditions in Minnesota, there are concerns of premature cracking and inferior durability in asphalt mixtures with lower asphalt binder contents. This research project evaluated 13 low asphalt binder content mixes from 10 actual field projects to determine whether there is potential for poor cracking performance and high permeability. Assessment of field performance indicated an average of 7.75 years of life until 100% transverse cracking level is reached. The pavement structure played a significant factor in controlling the cracking rates. Thin overlays showed almost ten times inferior transverse cracking performance as compared to asphalt wearing courses on full-depth reclamation. Asphalt mixture volumetric factors did not show a statistically significant effect on cracking rates; however, the asphalt binder grade did show a strong effect. Eight out of the 13 coarse asphalt mixtures evaluated in this study have higher permeability than the typical dense graded asphalt mixtures. Performance evaluations using lab measured properties predicted poor thermal cracking performances. No discernable trends were observed between measured or predicted cracking performance and mix volumetric measures. Use of performance tests based on specifications for design and acceptance purposes is reinforced through this study.
Investigation of Asphalt Mixtures Compaction Using a Novel Approach Based on Tribology
(Center for Transportation Studies, University of Minnesota, 2020-12) Yan, Tianhao; Turos, Mugurel; Kumar, Ravi; Marasteanu, Mihai
Compaction is one of the most important factors that affects the durability of asphalt pavements. Many studies have been focused on developing methods to improve compaction. Previously, the authors found that the addition of small percentages of Graphite Nanoplatelets (GNPs) significantly increase the compactability of asphalt mixture. Traditional viscosity test results show that the increase in compactability is not a result of viscosity reduction, which implies that other mechanisms are responsible for the increase in compactability of GNP modified mixtures. This study investigates the lubricating behavior of the binder. A new test method, referred to as a tribological test, is conducted to evaluate the lubricating behavior of binders modified with different percentages of GNP (0%, 3%, and 6%). To better simulate the roughness of the aggregate surface, the tribological fixture is modified using textured contact surfaces instead of smooth ones. The results of rough surface tribological tests show that the addition of GNPs increases the lubrication behavior of the thin film binder between rough surfaces. It is hypothesized that the increase in compactability can be attributed to the increase in the lubricating behavior of the binder due to the addition of GNP.
Investigation of Cracking Resistance of Asphalt Mixtures and Binders
(Minnesota Department of Transportation, 2019-01) Marasteanu, Mihai; Turos, Mugurel; Ghosh, Debaroti; Matias de Oliveira, Jhenyffer Lorrany; Yan, Tianhao
In this study, the viability of using three test methods for asphalt mixtures and one test method for asphalt binders are investigated. These test methods are: Bending Beam Rheometer (BBR) for creep and strength of asphalt mixtures; low temperature Semi Circular Bend (SCB) test for fracture energy of asphalt mixtures; Dynamic Modulus (E*) test of asphalt mixtures using the Indirect Tensile Test (IDT) configuration; and BBR strength test of asphalt binders. The materials used in the experimental work were used in MnROAD cells constructed in the summer of 2016 as part of the MnROAD Cracking Group (CG) experiment, a 3-year pooled-fund project. The results show that the testing methods investigated provide repeatable results that follow trends similar to the one observed using traditional methods. The results also show that the properties are highly temperature dependent and the ranking observed at one temperature can change at a different temperature. In addition, it is observed that materials with similar rheological properties, such as complex modulus absolute value |E*|, creep stiffness S, and m-value, do not necessarily have the same fracture resistance. These results confirm one more time the need for a fracture/strength test for correctly evaluating cracking resistance of asphalt materials.
Investigation of Large-Stone Mixtures
(1993-12) Newcomb, Dave; Wei, Zhang; Stroup-Gardiner, Mary
This report presents the results of a one-year study on large-stone asphalt mixtures (LSAM). A thorough review of the existing technology regarding materials, mix design, and performance is included. This study expanded upon the body of knowledge by exploring an easier means of mixture design and explaining the fundamental properties of large-stone mixtures with respect to the aggregate gradation. It was found that a dense LSAM gradation possesses better strength and durability properties than a more open LSAM gradation. Furthermore, a mix design methodology is presented wherein the optimum asphalt content for the mixture may be determined on the basis of aggregate and compacted sample properties. This eliminates the need for cumbersome Marshall stability and flow measurements. The frequency dependency of large-stone mixtures is more pronounced at low temperatures than that of a conventional mixture. The tendency for thermal cracking should be lower for a LSAM than for a conventional mixture. Finally, recommendations are made to develop a permissive specification for LSAM, and to adopt the volumetric mixture design procedure outlined in the report.
Investigation of Low Temperature Cracking in Asphalt Pavements National Pooled Fund Study 776
(Minnesota Department of Transportation, 2007-10) Marasteanu, Mihai; Zofka, Adam; Turos, Mugur; Li, Xinjun; Velasquez, Raul; Li, Xue; Buttlar, William; Paulino, Glaucio; Braham, Andrew; Dave, Eshan; Ojo, Joshua; Bahia, Hussain; Williams, Christopher; Bausano, Jason; Gallistel, Allen; McGraw, Jim
Good fracture properties are an essential requirement for asphalt pavements built in the northern part of the US and in Canada for which the predominant failure mode is cracking due to high thermal stresses that develop at low temperatures. Currently, there is no agreement with respect to what experimental methods and analyses approaches to use to investigate the fracture resistance of asphalt materials and the fracture performance of asphalt pavements. This report presents a comprehensive research effort in which both traditional and new experimental protocols and analyses were applied to a statistically designed set of laboratory prepared specimens and to field samples from pavements with well documented performance to determine the best combination of experimental work and analyses to improve the low temperature fracture resistance of asphalt pavements. The two sets of materials were evaluated using current testing protocols, such as creep and strength for asphalt binders and mixtures as well as newly developed testing protocols, such as the disk compact tension test, single edge notched beam test, and semi circular bend test. Dilatometric measurements were performed on both asphalt binders and mixtures to determine the coefficient of thermal contraction. Discrete fracture and damage tools were utilized to model crack initiation and propagation in pavement systems using the finite element method and TCMODEL was used with the experimental data from the field samples to predict performance and compare it to the field performance data.
Investigation of Low Temperature Cracking in Asphalt Pavements National Pooled Fund Study – Phase II
(Minnesota Department of Transportation, 2012-08) Marasteanu, Mihai; Buttlar, William; Bahia, Hussain; Williams, Christopher; Moon, Ki Hoon; Teshale, Eyoab Zegey; Falchetto, Augusto Cannone; Turos, Mugurel; Dave, Eshan; Paulino, Glaucio; Ahmed, Sarfraz; Leon, Sofie; Braham, Andrew; Behnia, Behzad; Tabatabaee, Hassan; Velasquez, Raul; Arshadi, Amir; Puchalski, Sebastian; Mangiafico, Salvatore; Buss, Ashley; Bausano, Jason; Kvasnak, Andrea
The work detailed in this report represents a continuation of the research performed in phase one of this national pooled fund study. A number of significant contributions were made in phase two of this comprehensive research effort. Two fracture testing methods are proposed and specifications are developed for selecting mixtures based on fracture energy criteria. A draft SCB specification, that received approval by the ETG and has been taken to AASHTO committee of materials, is included in the report. In addition, alternative methods are proposed to obtain mixture creep compliance needed to calculate thermal stresses. Dilatometric measurements performed on asphalt mixtures are used to more accurately predict thermal stresses, and physical hardening effects are evaluated and an improved model is proposed to take these effects into account. In addition, two methods for obtaining asphalt binder fracture properties are summarized and discussed. A new thermal cracking model, called "ILLI-TC," is developed and validated. This model represents a significant step forward in accurately quantifying the cracking mechanism in pavements, compared to the existing TCMODEL. A comprehensive evaluation of the cyclic behavior of asphalt mixtures is presented, that may hold the key to developing cracking resistant mixtures under multiple cycles of temperature.
Laboratory Performance Test for Asphalt Concrete
(Center for Transportation Studies University of Minnesota, 2015-06) Dave, Eshan
The asphalt mixture design and acceptance procedures for Minnesota Department of Transportation are currently governed primarily by the mixture composition requirements put forth through use of various volumetric measures (such as, air content, asphalt film thickness, aggregate gradation etc.). The asphalt binder has been required to meet performance criteria through the Superpave asphalt binder specifications. This study looked at use of laboratory performance test for asphalt mixtures. The study was conducted in three phases, first phase focused on merging the asphalt mix design records with the pavement performance data to determine effects of mix design parameters on asphalt pavement cracking performance. Second and third phase used a series of field sections across Minnesota to conduct field performance evaluations as well as laboratory tests on field cored samples. The testing for second and third phase of the study focused on using disk-shaped compact tension (DCT) fracture energy test as a laboratory performance test. The findings form he first phase of study indicated that the asphalt binder type as defined by the Superpave performance grade (PG) plays an important role in affecting the field cracking performance, majority of mixture design parameters did not indicate a consistent effect on field cracking performance, this reinforces the need for use of laboratory performance test as a mixture design tool as well as acceptance parameter. The DCT testing results showed trends consistent with previous and other on-going research studies, whereby the asphalt mixtures with higher fracture energies corresponded with pavements with lower amount of transverse cracking.
A Mechanistic Design Approach for Graphite Nanoplatelet (GNP) Reinforced Asphalt Mixtures for Low-Temperature Applications
(Minnesota Department of Transportation, 2018-01) Le, Jia-Liang; Marasteanu, Mihai; Hendrickson, Rebecca
This report explores the application of a discrete computational model for predicting the fracture behavior of asphalt mixtures at low temperatures based on the results of simple laboratory experiments. In this discrete element model, coarse aggregates are explicitly represented by spheres, and these spheres are connected by bonds representing the fine aggregate mixture, a.k.a. FAM, (i.e. asphalt binder with the fine-size aggregates). A literature review examines various methods of computational modeling of asphalt materials, as well as the application of nanomaterials to asphalt materials. Bending beam rheometer (BBR) tests are performed to obtain the mechanical properties of the fine aggregate mixture (FAM) at low temperatures. The computational model is then used to simulate the semi-circular bend (SCB) tests of the mixtures. This study considers both the conventional asphalt materials and graphite nanoplatelet (GNP) reinforced asphalt materials. The comparison between the simulated and experimental results on SCB tests shows that by employing a softening constitutive model of the FAM the discrete element model is capable of predicting the entire load-deflection curve of the SCB specimens. Based on the dimensional analysis, a parametric study is performed to understand the influence of properties of FAM on the predicted behavior of SCB specimens.
Moisture Sensitivity in Asphalt Concrete Mixtures
(Minnesota Department of Transportation, 1995-11) Stroup-Gardiner, Mary; Newcomb, David E.; Crow, Benita; Kussman, William; Wegman, Dan
The research performed for this report was intended to recommend alternative mix design procedures and parameters for evaluation of asphalt mixture sensitivity, with more of an emphasis on volumetric relationships. Three Mn/DOT projects were selected to represent the following durability issues: 1) debonding of asphalt from aggregate, 2) cohesion problems, and 3) mix design problems. Materials were obtained from these construction projects and evaluated in the laboratory. Gradations were varied from the project specifications so that mixtures with more and less asphalt were evaluated along with the project mixture. Testing included the temperature susceptibility and moisture sensitivity of the mixtures, in addition to the net adsorption test on the aggregates. The results suggested means for identifying moisture sensitivity mechanisms in mixtures during the mixture design phase, although these need to be confirmed through more extensive investigation. Aggregate mineralogy, gradation, and mixture proportioning can all play a role in improving the durability characteristics of asphalt mixtures. Recommendations are made for continued research and implementation of an improved approach to asphalt mixture design.
Optimizing Asphalt Mixtures for Low-volume Roads in Minnesota
(Minnesota Department of Transportation, 2023-08) Barman, Manik; Dhasmana, Heena; Manickavasagan, Vishruthi; Marasteanu, Mihai
Minnesota has a large number of low-volume asphalt roads. These roads typically fail because of environmental factors, such as frigid temperatures, freeze-thaw cycles, and seasonal and daily temperature variations. The goal of this study was to suggest modifications to asphalt mixture designs currently used for low-volume roads in Minnesota to improve the resistance of the mixes against the environmentally driven distresses. The study was conducted by accomplishing multiple tasks, such as a literature review, online survey, fieldwork studying the cause of the asphalt pavement distresses, laboratory work comparing asphalt mixtures designed with Superpave-4, Superpave-5, and regressed air voids methods, and studying the field compaction of Superpave-5 mixes. The mechanical performance of the asphalt mixes was studied by conducting Disc-Shaped Compact Tension (DCT), Indirect Tensile Strength (ITS), and Dynamic Modulus (DM) tests. The study included both laboratory- and plant-produced mixes. The study found that asphalt layers for the low-volume roads did not get enough densification, which augments environmentally driven distresses, such as thermal cracks, and longitudinal joint cracks. The Superpave-5 method holds considerable promise for the design of asphalt mixtures for low-volume roads in Minnesota, which may likely increase the asphalt layer densification and mitigate some of the common distresses.
Rheology of Granular-Fluid Systems and Its Application in the Compaction of Asphalt Mixtures
(2019-04) Man, Teng
The United States has more than 2.7 million miles of paved roads, of which 94\% are surfaced with asphalt pavement. The resilience and durability of asphalt materials have important consequences for transportation safety. Previous research showed that the porosity, i.e. the fraction of air voids in an asphalt pavement, which is largely influenced by the compaction during the installation process, has a significant influence on the durability of installed asphalt pavements. Therefore, understanding the compaction process of asphalt mixtures has become an essential topic of research. However, the existing modeling approaches are mostly phenomenologically based. Very few studies have focused on developing a physics-based predictive model for the compaction of asphalt mixtures. The development of a physics-based computational model is complicated by the complexity and variability of the asphalt mixture. Asphalt mixtures consist of (1) aggregates (sand, pebbles, and rocks) up to 3\ cm in size, (2) fine aggregate mixtures or FAM consisting of the sand portion of the aggregates, asphalt binder, and other additives coats. During the compaction process, the FAM surrounds the coarser aggregates and ultimately as the mixture cools and solidifies, binds them like glue. The details of each component vary considerably across the country. Part of the difficulty in modeling the compaction of such a complex multiphase mixture is to developing reliable rheology for the constitutive behavior of the mixture. In this study, we developed a multi-scale discrete element method (DEM) model for compaction of asphalt mixtures. The model is anchored by the representation of the asphalt as a two-phase mixture: (1) liquid-like FAM and (2) individual gravel particles. On the macroscopic level, only coarse (large) aggregates are considered in the simulation as non-spherical particles. The interaction between these aggregates is mediated both by the coarse particle properties and the properties of the interstitial fluid-like slurry FAM. We derive the dependence of the FAM rheology to the fluid properties of the asphalt binder and the solid properties of the finer particles using discrete element model (DEM) simulations. We use larger scale DEM simulations with coarse aggregates and the modeled FAM to model the gyratory compaction process of hot mixed asphalt with different viscosity of asphalt binder and different aggregate size distributions. The results of the thesis are comprised of three primary components described in this thesis: (1) the small scale model of particles and fluid which provide more macroscale and particle scale information about slurry flow behavior; (2) the larger multi-scale model framework of the asphalt compaction process itself as a process. The results can provide a systematic method for improving the mix design of asphalt mixtures and the compaction procedures toward a more efficient compaction process.

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