Dominant Aggregate Size Range Research Articles

Study on stochastic behavior of particle system in hot mix asphalt mixture from a meso-structural perspective

The variability and uncertainty bring great trouble to the application and in-depth research of asphalt mixture. This study aimed to detect the microstructural differences between the asphalt specimens after fixing the experimental and environmental inputs. To this end, the digital image correlation (DIC) method was utilized to propose reliable skeletal and disruptive meso-parameters. Besides, the close packing theory and digital sieving technique were combined to classify the internal particles of the mixture structure. Afterward, the stochastic behaviors of the particle systems containing the dominant aggregate size range (DASR) and interstitial component (IC) aggregates were thoroughly discussed. Finally, the disruption effect of IC on the skeletal structure was also investigated. The analysis results show that the microstructure of the asphalt mixture was a typical random system with a great deal of contingency. The aggregate contact index (ACI) was the most variable among the overall skeletal parameters, with a variation coefficient (COV) of 13.24 %. Besides, almost all the microstructural indexes indicated that about 4% of the specimens in parallel tests showed significant variability behavior, e.g., Na,13.2 > Na,16.0. Besides, the microstructural uncertainty of the minority class, e.g., the 16-mm aggregates with a 4% ∼7% COV higher than the other classes, was particularly significant. Finally, the interference effect was proven to focus on the contact behavior of DASR particles, thus damaging the DASR-based system. This study not only emphasizes the impact of variability but provides implications for controlling the performance of asphalt pavement.

Mix design of large-stone asphalt mixtures for heavy-traffic roads

Heavy traffic and high temperatures are a common cause of rutting in paved areas, which reduces the time needed between pavement maintenance interventions. Large-stone asphalt mixtures (LSAMs) can reduce rutting when used as intermediate layers in pavement rehabilitation. LSAM is asphalt concrete with a nominal maximum aggregate size of at least 25 mm. In this study, we provide a brief literature review of the historical use of LSAMs, as well as the relevant characteristics of LSAM design. Three LSAMs were designed using different compaction methods: (i) Marshall compaction; (ii) rolling compaction; and (iii) Superpave gyratory compaction (SGC) by varying the compaction energy in 75, 100, and 125 gyrations. Depending on the mix design method used, the designed asphalt content ranged from 3.0 to 4.3%. The locking point from the SGC was evaluated at different gyratory compaction energies, which were related to the porosity of the dominant aggregate size range. These parameters are considered to be of great value when evaluating the LSAM design.

Gradation characteristics-based interlayer mixture design method for enhanced rutting resistance of asphalt pavements

The major role of interlayer mixtures is to mitigate reflective cracking by absorbing or dissipating concentrated stress, and relatively low-stiffness materials are typically used. However, there is a concern that interlayer mixtures may increase the risk of rutting because of these low-stiffness materials. The dominant aggregate size range (DASR) porosity has been successfully applied for structural mixtures to ensure enhanced rutting performance. This study mainly focused on developing new DASR porosity requirements for interlayer mixtures that ensures acceptable rutting performance in the mix design phase. Ten interlayer mixtures with a broad range of DASR porosities were evaluated using the asphalt pavement analyzer test. Our results indicated that the gradation characteristics of interlayer mixtures played an important role in rutting performance. Also, a relationship between DASR porosity and the rutting potential of interlayer mixtures was identified that resulted in the establishment of the preliminary DASR porosity requirements.

Laboratory Evaluation and Design of Construction and Demolition Wastes for Granular Base

Using recycled aggregate from construction and demolition (C&D) wastes as a construction material is a potential method for solving the disposal of C&D wastes, which can reduce the exploitation of natural aggregate. In this study, extensive laboratory tests were carried out to investigate the reliability of the C&D wastes used as road base material. Meanwhile, the gradation design and the dominant aggregate size range were considered, and a physical disposal method was proposed to enhance the structural performance of the recycled material by replacing the skeleton of the recycled aggregate (RA) with high-quality limestone. The test results showed that (1) given the high absorbency and fragility of C&D wastes, its RA was not enough to provide the strength and stability required by the base; (2) the compaction characteristics of the RA are quite different from that of the limestone aggregate, but the final compaction effect is basically the same; (3) the replacement treatment proposed in this study is an effective approach to improve the performance of the recycled granular base because the breakage rate decreased by at least 28.2% and the mechanical properties increased by approximately 50% compared with that of the untreated specimen; and (4) when the limestone content reached 75%, the California bearing ratio and the resilient modulus of the graded B specimen exceeded 120% and 200 MPa, respectively, satisfying the pavement requirement in medium traffic.

A tool to design rutting resistant asphalt mixes through aggregate gradation selection

This work focuses on the proposition of a simple tool to evaluate the quality of the grain size distribution and its potential to produce rutting resistant asphalt mixes. The tool is based on the hypothesis of the existence of a main aggregate structure responsible for absorbing and transmitting stresses without developing plastic deformation. Two parameters were proposed in this paper to characterize such a structure: α and C ratios. The first characterizes the degree of interlocking of this structure, called the Dominant Aggregate Size Range (DASR), while the latter is related to the amount of relatively bigger particles within this structure. The Flow Number (FN) was adopted as an indicator of the rutting resistance of 27 investigated asphalt mixes, varying in grain size distribution, aggregate origin, binder type, and binder content. The proposed parameters α and C are established as characteristic parameters of the aggregate skeleton of the asphalt mix, and are well correlated with FN, indicating they have the potential for being useful tools. However, they do not capture the importance of the asphalt binder for the rutting resistance. A third index, κ, is then established as a characteristic parameter of the asphalt mix associated with the rutting resistance. It is a combination of the gradation parameters (α and C), binder content and binder viscosity. An excellent correlation was observed between the FN and the κ index. Finally, criteria for the κ index were suggested as a function of traffic level, as it is conventionally done for FN values. Results from this work contribute to the development of rational tools to design resistant and stable aggregate gradation compositions for higher quality pavements.

Monitoring permeability potential of hot mix asphalt via binary aggregate packing principles correlated with Bailey ratios and porosity principles

Asphalt mix designs tend to optimise the load transfer via aggregate skeletons as main mechanism to provide rut resistance, often to the detriment of durability. Permeability, as a significant durability indicator, is more difficult to measure in the field than in the laboratory. Voids in the asphalt mix have a critical zone where an increase in voids is exponentially linked to permeability. This zone is where voids start to become increasingly interconnected. The aggregate grading envelope characteristics can provide an indication of the interconnectedness of the voids to enhance quality control. New rational Bailey Method Ratios (BMRs) were defined with contiguous aggregate fractions in the numerator and denominator. This allows also for porosity calculation using the Dominant Aggregate Size Range (DASR) method. The Binary Aggregate Packing (BAP) triangle porosity diagrams provide insight into the link between porosity and interconnected voids. The wall and the loosening effects create additional porosity (voids) with increased probability of interconnectedness. Clear threshold zones of interconnected voids can be determined with BAP coarse/fine mass ratios. The latter is the inverse of the rational BMRs. It allows for simple spreadsheet calculations of porosity and coarse/fine mass ratio as a screening tool for probable permeability via benchmark analysis. Reworked data sets demonstrated how the inverse of BMRs could show potential for interconnectedness of voids and, therefore, permeability propensity.

Fracture-Tolerant and Shear-Resistant Interlayers for Mitigation of Reflective Cracking

Reflective cracking is frequently reported as the most common distress affecting resurfaced pavements. An asphalt rubber membrane interlayer (ARMI) approach has been traditionally used in Florida to mitigate reflective cracking. However, recent field evidence has raised doubts about the effectiveness of the ARMI when placed near the surface, indicating questionable benefits to reflective cracking and increased instability rutting potential. The main purpose of this research was to develop guidelines for an effective alternative to the ARMI for mitigation of near-surface reflective cracking in overlays on asphalt pavement. Fourteen interlayer mixtures, covering three aggregate types widely used in Florida, and two nominal maximum aggregate sizes (NMAS) were designed according to key characteristics identified for mitigation of reflective cracking, that is, sufficient gradation coarseness and high asphalt content. The dominant aggregate size range—interstitial component (DASR-IC) model was used for the design of all mixture gradations. A composite specimen interface cracking (CSIC) test was employed to evaluate reflective cracking performance of interlayer systems. In addition, asphalt pavement analyzer (APA) tests were performed to determine whether the interlayer mixtures had sufficient rutting resistance. The results indicated that interlayer mixtures designed with lower compaction effort, reduced design air voids, and coarser gradation led to more cost-effective fracture-tolerant and shear-resistant (FTSR) interlayers. Therefore, preliminary design guidelines including minimum effective film thickness and maximum DASR porosity requirements were proposed for 9.5-mm NMAS (35 µm and 50%) and 4.75-mm NMAS FTSR mixtures (20 µm and 60%) to mitigate near-surface reflective cracking.

A comparative analysis of the fracture performance of wearing course mixtures under different geometries, compactions, and aggregate gradations

ABSTRACT For more than one decade, the simplicity of the notched semi-circular bending (SCB) test has gained increasing interest in evaluating the fracture characteristics of asphalt mixtures. This study investigated if the notched SCB test presents a viable alternative to the three-point bending beam (TPBB) test for assessing fracture properties of asphalt mixtures at intermediate temperature conditions. The TPBB test was conducted using the JRA B005 standard, and the notched SCB test was performed using the following three standards: EN 12697-44, AASHTO TP 105-13, and AASHTO TP 124-16. In addition, this analysis investigated the cracking resistance of a variety of dense-, coarse-, and fine-graded mixtures with a 12.5-mm nominal maximum particle size. The experiments showed that the notched SCB test using the EN 12697–44 standard may be able to replace the TPBB test for assessing the cracking resistance of asphalt mixtures. This study also examined the effects of aggregate gradation and asphalt content on the cracking performance of asphalt mixtures using the characteristics of continuous maximum density, the dominant aggregate size range model, and apparent film thickness.

Avaliação laboratorial do tipo e teor de ligante e da granulometria na deformação permanente de misturas asfálticas

Este trabalho avaliou a influência na deformação permanente do tipo e teor de ligante asfáltico e da granulometria quanto ao método Bailey, Faixa de Agregado Dominante (FAD) e faixas granulométricas B e C por meio do ensaio uniaxial de carga repetida. Para isso utilizaram-se três ligantes asfálticos, 50/70, AMP 60/85 e o Highly Modified Asphalt (HiMA), quatro granulometrias, sendo duas Faixa B e duas C, e dois métodos de dosagem, Superpave e Marshall, totalizando 24 misturas asfálticas. Os resultados indicaram que as modificações no tipo e no teor dos ligantes asfálticos foram mais influentes na deformação permanente do que a granulometria das misturas, inclusive encontrou-se boa correlação entre a reologia dos ligantes e os Flow Numbers (FNs) obtidos. O método Bailey apresentou-se mais efetivo em conferir ganho de resistência comparado ao método FAD e a utilização da granulometria faixa B não resultou em um melhor comportamento comparado a uma granulometria faixa C.

Effect of aggregate gradation on the cracking performance of wearing course mixtures

Cracking is one of the main failure mechanisms of asphalt pavements. This study investigates the effects of aggregate gradation on the cracking performance of hot mix asphalt (HMA) mixtures at two stages, i.e., the cracking initiation and cracking propagation stages. Based on the continuous maximum density (CMD) of aggregate gradation and the dominant aggregate size range (DASR) model, a novel cracking performance index—designated the gradations-based cracking resistance index (GCI)—was developed to easily evaluate the cracking resistance of wearing course mixtures. This simple index was applied to comparatively investigate cracking resistance in a variety of dense-, coarse-, and fine-graded mixtures with 12.5-mm nominal maximum particle size. Seven blends of different aggregate gradations were developed using the conventional Marshall mix design method. This study employed the notched semi-circular bending test to evaluate the cracking resistance of the HMA mixtures. The experiments demonstrated a strong relationship between GCI and cracking resistance at the cracking initiation stage. In addition, cracking resistance was observed to increase with increasing GCI value. These findings indicate that the novel index has potential applications for evaluating the cracking performance of wearing course mixtures.

Evaluation of the effect of segregation on coarse aggregate structure and rutting potential of asphalt mixtures using Dominant Aggregate Size Range (DASR) approach

Segregation of asphalt mixtures indicates an artificially altered aggregate gradation, which consists of excessive coarse aggregates and insufficient fine aggregates that may result in premature failures and eventually reduce the pavement service life. Since segregation may cause a significant change in aggregate structure of asphalt mixtures, segregated mixtures may exhibit an increased potential for rutting among all other distresses. However, the effect of segregation on rutting potential has not been clearly identified. In this study, the effect of segregation on change in aggregate gradation (particularly for coarse aggregate structure) that may negatively affect the rutting potential of asphalt mixtures was evaluated. The Dominant Aggregate Size Range (DASR) gradation model and the DASR porosity parameter found to be well correlated with rutting performance of asphalt mixtures were employed for evaluation. A total of four field sections exhibiting different severities of segregation were selected and evaluated. Results of laboratory testing and DASR analysis indicated that segregated mixtures caused a significant shift in aggregate gradation, especially for coarse aggregate portion of the mixture gradation, which may result in significantly increased the potential for rutting. The results obtained from laboratory tests and the DASR approach were then compared and verified with those of actual filed rutting performance.

Evaluation of cracking performance for polymer-modified asphalt mixtures with high RAP content

Fourteen reclaimed asphalt pavement (RAP) mixtures designed with different combinations of RAP sources, contents (up to 40%) and mixture conditioning levels were evaluated to determine the maximum allowable amount of RAP material in surface courses without jeopardising pavement cracking performance. Extracted RAP binder was blended with virgin polymer-modified asphalt (PMA) binder at various RAP binder replacement ratios. All blends behaved effectively as PMA binder as they met the multiple stress creep recovery (MSCR) %recovery requirement, and in addition they had satisfactory binder fracture energy density values. RAP gradation was found to significantly affect the fracture properties of RAP mixtures as it controls the distribution of RAP binder and potentially the degree of blending between virgin and RAP binder. Increased RAP content resulted in stronger (i.e. higher tensile strength) but more brittle (i.e. lower failure strain and lower mixture fracture energy) mixtures. However, after long-term oven ageing (LTOA) plus cyclic pore pressure conditioning (CPPC) which was used to simulate long-term field ageing conditioning, all RAP mixtures still exhibited dissipated creep strain energy to failure (DCSEf) values above 0.75 kJ/m3 and energy ratio (ER) values well above 1.0, indicating acceptable cracking performance. It must be emphasised that all RAP mixtures had good gradation characteristics as they all met Superpave design criteria and dominant aggregate size range and the interstitial component (DASR-IC) requirements. Therefore, satisfactory inclusion of up to 40% RAP was acceptable for well-designed PMA mixtures.

Effectiveness of dominant aggregate size range – interstitial component criteria for consistently enhanced cracking performance of asphalt mixtures in the field

This study primarily focused on evaluating the effectiveness of dominant aggregate size range – interstitial component (DASR-IC) criteria established for the purpose of asphalt mixture design and construction specifications leading to better and consistently enhanced field cracking performance using the enhanced hot-mix asphalt fracture mechanics-based performance prediction model (HMA-FM-E model) plus field performance evaluation. Results indicated that the mixtures meeting all DASR-IC criteria, including DASR porosity, disruption factor (DF), effective film thickness (EFT), and fine aggregate ratio (FAR), will have relatively better and consistently enhanced field cracking performance. The mixtures not meeting all DASR-IC criteria show inconsistent field cracking performance, including either cracked or uncracked status. Thereby, it is important to design asphalt mixtures that meet all DASR-IC criteria. The DASR-IC criteria were found to be effective and their implementation will help ensure consistently enhanced cracking performance in the field.

Enhanced Gradation Guidelines to Improve Asphalt Mixture Performance

In 2010 a theoretical approach to the evaluation and specification of aggregate gradations to resist rutting was evaluated by the Florida Department of Transportation by accelerated pavement testing. This approach, known as the dominant aggregate size range (DASR) gradation model, provides a framework to ensure that the coarse aggregate of the resulting mixture has sufficient aggregate interlock to resist permanent deformation. Further research by the University of Florida and the Department of Transportation found that the properties of the interstitial components (ICs) within the DASR voids were strongly related to the durability and fracture resistance of asphalt mixtures. Parameters that made up the combined DASR-IC model included the DASR porosity, disruption factor (DF), effective film thickness (EFT), and fine aggregate ratio (FAR). The original evaluation of the DASR model was recently extended to include DASR gradations that might have had marginal aggregate interlock (i.e., marginal DASR porosity) and the effect of IC properties on mixture fracture resistance. The results confirmed that the rutting performance of the asphalt mixture was primarily controlled by the DASR porosity and that mixtures with marginal DASR porosity might still have had significantly better rutting performance than mixtures with poor DASR porosity. In addition, it was shown that the DASR porosity, DF, EFT, and FAR parameters played a critical role in mixture cracking performance. The validation of the combined DASR–IC model was documented, and the acceptable range of each parameter for improved mixture rutting and cracking performance was confirmed.

Disruption factor of asphalt mixtures

Typically, aggregate gradation is selected to meet Superpave mix design specification; however, many Superpave mixtures have exhibited deficient field performance. The porosity of the dominant aggregate size range (DASR), which is the primary structural network of aggregates, has been extensively validated as a tool to evaluate coarse aggregate structure of laboratory and field asphalt mixtures. Mixtures identified by the system as having poor or marginal gradations resulted in poor rutting resistance. This study focused on how asphalt mixture performance is affected by changes in interstitial component (IC), which is the material between DASR particles. Laboratory testing clearly showed that IC characteristics may have a significant effect on rutting and cracking performance of mixtures. The disruption factor (DF) was developed to evaluate the potential of IC aggregates to disrupt the DASR structure. DF satisfactorily distinguished poor performing mixtures; therefore, it may eventually be used in combination with DASR porosity as a design parameter for rutting and cracking resistant asphalt mixtures.

Effect of Gradation Characteristics on Performance of Superpave Mixtures in the Field

Previous studies have indicated that existing mix design criteria, including voids in mineral aggregates, gradation control points, and effective asphalt content, do not capture all critical aspects of gradation and mixture volumetric properties found to be strongly related to rutting and cracking performance. The performance of Superpave® mixtures varied significantly in mixtures that met all existing criteria. Therefore, there was a need to identify and verify additional criteria that could ensure better and more consistent performance of Superpave mixtures. Four parameters from the dominant aggregate size range (DASR)– interstitial component (IC) model have been determined to relate well to field performance of Superpave mixtures: DASR porosity, disruption factor (DF), effective film thickness (EFT), and the ratio of coarse portion to fine portion of fine aggregate (CFA/FFA). These four parameters were used in a field performance evaluation of rutting and cracking that was conducted to identify performance-related criteria. Results indicated that DASR porosity, which reflected the characteristics of coarse aggregate structure, was the most dominant parameter to control rutting performance. IC characteristics including DF, EFT, and CFA/FFA could not overcome the problems associated with a mixture that had DASR porosity outside the acceptable range. However, IC characteristics were more important than DASR porosity to differentiate clearly field cracking performance. The DF criteria should be considered in conjunction with EFT and CFA/FFA criteria to distinguish effectively the field cracking performance. Therefore, the introduction of DASR-IC criteria into current mix design guidelines and specifications will help to ensure good field rutting and cracking performance of Superpave mixtures.

Porosity of the Dominant Aggregate Size Range to Evaluate Coarse Aggregate Structure of Asphalt Mixtures

This paper presents the results from an evaluation of a new gradation-based framework developed for identifying and assessing the coarse aggregate structure of dense-graded mixtures for resistance to rutting. A theoretical packing-based analysis procedure was used to evaluate the coarse aggregate structure for hot mix asphalt mixtures. This procedure was applied to an extensive range of mixtures. A key feature of this new framework is the concept of the existence of a dominant aggregate size range (DASR). The porosity of the DASR is calculated based on an interaction diagram to evaluate the degree of particle-to-particle interaction of coarse aggregates between contiguous sieve sizes. In addition, an interaction diagram-based criteria for dense-graded Superpave mixtures are determined, as well as criteria for the porosity of the DASR. Based on the field and laboratory-based rutting performance of the mixtures evaluated in this paper, it was concluded that DASR along with the porosity of the DASR may provide a framework for evaluating the gradation of dense graded mixtures for their likely rutting potential.

Laboratory Evaluation for Rutting Performance Based on the DASR Porosity of Asphalt Mixture

ABSTRACT Researchhas shown that gradation characteristics determine whether the aggregate structure in asphalt mixture results in good performance. A recent study indicated that large enough aggregates should engage dominantly to form an aggregate structure that can resist deformation; also, a new approach identified the porosity of the Dominant Aggregate Size Range (DASR) as the key parameter that determines whether or not a particular gradation results in a suitable aggregate structure. This paper presents a laboratory experiment to evaluate the DASR porosity in terms of its ability to identify unsuitable aggregate structures. Eight dense-graded Superpave mixtures were designed using two aggregate types (limestone and granite). For each aggregate type, mixtures with varying DASR porosity were produced and tested to evaluate laboratory rutting resistance. Test results indicated that the new approach successfully separated mixtures according to their observed laboratory rutting performance, indicating that DASR porosity can serve as an effective parameter to evaluate aggregate structure.