Dense-graded Asphalt Concrete Research Articles

Experimental Analysis of Noise Characteristics on Different Types of Pavements inside and outside Highway Tunnels

Aiming to reduce noise pollution and optimize the acoustic quality in highway tunnels, the noise characteristics on different types of pavements were analyzed and compared in this research, based on the on-site noise measurement in two tunnels with the free fields as a control group. Specifically, the noise characteristics include two aspects: various noise and noise time attenuation performance. Various noise includes on-board sound intensity (OBSI) noise and cabin noise. The noise time attenuation performance uses the indicator of reverberation time. Three types of pavements were measured, including dense-graded asphalt concrete (DAC) and single-layered and double-layered porous asphalt (PA) pavement. The results showed that, for the same type of pavement, compared with the free fields, the difference in OBSI noise in tunnels was within a range of less than 1 dBA; the cabin noise increased by 3.4 dBA~6.6 dBA. The noise level in tunnels was greater than that outside tunnels, and the longer tunnel exhibited higher traffic noise and worse noise time attenuation performances. For the same tunnel, PA pavement could reduce the cabin noise by 3.8 dBA~6.7 dBA. PA pavement also exhibited shorter reverberation time. The application of PA pavement could effectively improve the acoustic quality in the tunnel. This research contributes to noise pollution abatement and the improvement of the comfort and safety of drivers in tunnels.

Influence of Interaction between Microcracks and Macrocracks on Crack Propagation of Asphalt Concrete.

This paper aims to reveal the interaction relationship between microcracks and macrocracks and the influence of the interaction on the crack propagation behavior. A theoretical model of asphalt concrete was established for the interaction between microcracks with different crack densities and a macrocrack. And a meso-structure model of AC-13 dense-graded asphalt concrete was established by combining the Talyor medium method and the DEM (discrete element method). Macro and micro parameters, such as the stress-strain characteristics, crack evolution parameters, and crack tip stress field, were obtained through a semi-circular bend virtual test and used to study the characteristics of crack propagation under the interaction between microcracks and the macrocrack. The results indicate that the interaction has an effect throughout the process of asphalt concrete damage, and shows shielding and acceleration effects as the microcrack density changes. When the microcrack density is low (f3 ≤ 0.8), the crack propagation process, which is affected by the interaction effect, exhibits significant differences, and the interaction effect shows the shielding effect. When the microcrack density is high (f3 > 0.8), the fracture stage is mainly affected by the interaction effect, which shows the acceleration effect. The results provide a predictive theoretical and numerical model for low-temperature cracking of asphalt pavement, and theoretical support for the design, maintenance, and upkeep of long-life pavement.

Evaluation of asphalt film thickness and heavy metal leaching of oxidizing slag used as an aggregate material in dense-graded asphalt concrete.

Electric-arc-furnace (EAF) steelmaking uses scrap iron and steel as raw materials. Scrap iron and steel originate from complex sources and may contain heavy metal components which can leach into the environment over time due to wear-and-tear. A by-product of the EAF steelmaking process is oxidizing slag, and approximately 1.2 million metric tons is produced every year in Taiwan alone. This study investigated substitution of natural aggregates with oxidizing slag in dense-graded asphalt concrete. We evaluated the water resistance and asphalt film thickness of the oxidizing slag substituted asphalt concrete and further explored the performance of oxidizing slag as paving material. We determined the dissolved and total amounts of heavy metals in the oxidizing slag, comparing these results with current regulatory controls to assess the environmental compatibility of the oxidizing slag. We found that due to the complicated sources of oxidizing slag, the basic properties should be analyzed on a batch-to-batch basis. Furthermore, we recommend trial mixing before upscaling the production of oxidizing slag substituted dense-graded asphalt concrete to confirm the mixing time required to achieve uniformity. The results also show that in comparison to natural aggregates used in asphalt concrete, oxidizing slag exhibits superior performance in terms of increased asphalt film thickness and improved water resistance. Furthermore, oxidizing slag as an aggregate material was associated with decreased heavy metal leaching and reduced environmental pollution. The results of the toxicity characteristic leaching procedure (TCLP) met regulatory requirements. However, the microwave-assisted aqua-regia digestion procedure showed heavy metal concentrations exceeding the monitoring standards for food crops. Considering environmental compatibility, it is recommended that controlling the total amount of heavy metals in oxidizing slag should be included in regulatory requirements. Furthermore, we should prohibit the use of materials such as oxidizing slag and other steel furnace slag in the roadways adjacent to edible crop farmlands.

Effects of Pavement Texture Characteristics on Tire–Pavement Noise from Dense-Graded Asphalt Concrete Pavement

Effects of Pavement Texture Characteristics on Tire–Pavement Noise from Dense-Graded Asphalt Concrete Pavement

The driving mechanism of cement hydrated products leaching on as-built cement concrete bridge deck pavements

Recently, a new distress type in as-built dense-graded asphalt concrete (DGAC) paved on concrete bridge decks, namely alkali leaching, has been detected in China. The water carries dissolved alkali ions from the cement concrete deck to the pavement surface and reacts with CO2 in the air to form whitish carbonate deposits. The “bottom-up” water transportation process in the presence of the natural environment without vehicle loading effect is a complicated problem. Thereby, scrutiny of the driving force of the “bottom-up” water transportation process in cement concrete bridge deck pavements (CCBDPs) plays a vital role in realizing the mechanism of alkali leaching. In the present study, three potential driving mechanisms that may cause this process are proposed and simulated in the laboratory, including water vapor diffusion under action of multiple temperatures and relative humidity (RH), capillary rise, and leaching water caused by variation of atmospheric pressure. The microstructure of alkali leaching samples cored from distress pavement is also carefully examined by X-ray CT. The obtained results show that the diffusion mass of water vapor demonstrates a rapid lessening with the reduction of the relative humidity differences. A highly linear correlation between the RH difference and the diffusion flux of the water vapor for different temperatures is also identified, indicating that the DGAC with various air voids follows Fick’s first law of diffusion. Further, capillary rise indeed occurs in the DGAC but does not contribute to the alkali leaching process. The pressure difference could continuously drive the leaching water to the surface of DGAC samples, and the critical pressure difference (0.3–0.7 kPa) would be generally less than the daily variation of the atmospheric pressure (approximately 0.8 kPa in weather alternate days). The quantitative analysis of the internal structure for alkali leaching cores also reveals that the distressed cores present relatively higher void ratios, especially for small volume and narrow pores. The entrapped air within unsaturated pores provides the precondition for water transport subjected to the atmospheric pressure differences. These findings contribute to the understanding of static moisture transportation in the dense-graded asphalt mixtures and clarify the main driving mechanism of moisture-induced alkali leaching on CCBDPs.

Analysis of alkali leaching mechanism on as-built cement concrete bridge deck pavement

A new distress type, namely alkali leaching, was recently observed to have developed on an as-built dense-graded asphalt concrete (DGAC) paved on a cement concrete bridge deck in China. Not only does alkali leaching affect the aesthetic appearance of the cement concrete bridge deck pavement (CCBDP) due to the distinctive color contrast, it also creates a potential threat to the service life of the bridge. In this paper, an alkali leaching distressed section of a CCBDP in Shaanxi Province (China) was studied. The study results indicated that whitish spots cannot be removed by natural water. In situ pH measurements indicated highly alkalinine materials appear on the surface of pavement layers. Based on these findings, the formation mechanism of alkali leaching on CCBDP was analyzed. The corresponding results showed that the main mineral of alkali leaching was Calcium Carbonate (CaCO3). Under wet conditions, rainwater infiltrates into the cement bridge deck from the sides of the pavement. Continuous exposure to moisture or humid environments facilitates the subsequent hydration to generate Ca(OH)2, which is the alkaline source for alkali leaching. The generated Ca(OH)2 migrates with rainwater to the pavement surface through capillary action. With the repeated circles of wet and dry conditions, the in-situ carbonation products lead to formation of alkali leaching on the pavement surface.

Laboratory Assessment of Dense Graded Asphalt Concrete Incorporating Coal Furnace Ash in South of Vietnam

Currently, application of industrial waste or by-product in road construction industrials is a major interest by researchers, government officers and engineers. Coal ashes by-product from industrial parks negatively impact environment, costly in treatment, and require large ground for disposing areas. Therefore, this paper proposes on using the coal ash from furnace products of an industrial park in South of Vietnam to be incorporated into dense graded asphalt concrete using Nominal Maximum Aggregate Size 12.5mm. Laboratory performance tests including Marshall stability, indirect tensile strength, Cantabro loss, and dynamic fatigue test were conducted. The effects of coal ash contents in replacement of fine aggregate which is passing 4.75mm sieve from asphalt mixture into laboratory performance of mixture is also discussed in detail.

ЧИСЛЕННЫЙ РАСЧЕТ НЕЖЕСТКОЙ ДОРОЖНОЙ ОДЕЖДЫ НА ПРОЧНОСТЬ И СДВИГОУСТОЙЧИВОСТЬ МЕТОДОМ КОНЕЧНЫХ ЭЛЕМЕНТОВ

The paper presents 2D mathematical simulation results for a T–90 tank interacting with the III-type road in a plane-strain formulation. The purpose of the work is to determine the vertical deflection of an asphalt-concrete road, as well as the load factor of the two-layer road pavement (dense-graded asphalt concrete, open-graded asphalt concrete) and two-layer roadbed (gravel roadbed, ground roadbed – silt sandy loam). To calculate the load factor of the road pavement, the ratio of the von Mises stress to the ultimate compression stress is used. To analyze the shear resistance of the roadbed, the modified Drucker-Prager strength criterion is utilized. The computed results reveal the maximum vertical deflection in the contact area of the tracks. In the same area, the load factor of the road pavement is 3–12, which indicates the high bearing capacity of the dense-graded asphalt concrete. Analysis of the shear resistance of the roadbed shows that irreversible deformations occur in the gravel base in the contact area of the tracks, which can lead to the subsidence of the coating, while the load factor for sandy loam is 3–10.

Performance and Toxic Leaching Evaluation of Dense-Graded Asphalt Concrete Using Steel Slag as Aggregate

AbstractThe comparative performance between steel slag (S) and limestone (L) as aggregates in dense-graded asphalt concretes were investigated in this research. The performance tests for fatigue cr...

Estimating unconfined compressive behavior of HMA using soft computing

The mechanical properties of materials such as elastic tangential modulus (Et) and unconfined compressive strength (UCS) can be used to predict their performance during service life. This paper utilizes gene expression programming (GEP) as an alternative method to estimate the unconfined uniaxial compression properties of hot mix asphalt. Short-term static compression was used to evaluate modes of failure and stress–strain relationship of cylindrical and prismatic asphalt concrete specimens due to mixture types, specimen shape, height, temperature, binder type and testing orientation. The results show that cubic specimens tested parallel to the direction of compaction achieved higher compressive strength and peak strains than specimens tested to the perpendicular direction. Cylindrical specimens had greater elastic stiffness than prismatic specimens with similar aspect ratios. The GEP and multiple linear regression approaches for the assessment of UCS and Et concluded satisfactory outcomes. The coefficient of determination (R2) for USC-GEP was 0.887 and 0.908 and similarly Et-GEP of 0.785 and 0.648 was more significant than regression models. The models developed provide a cheap, simple and quick methodology of estimating the stress–strain properties of dense-graded asphalt concrete by eliminating the need for the compression test.

Road pavement design using the finite element method

The purpose of the work is to calculate the stress-strain state of the III-type road, as well as to determine the load factor for road pavement and roadbed. A model of non-rigid road pavement consisting of 4 layers is considered: dense-graded asphalt concrete, open-graded asphalt concrete, gravel roadbed, ground roadbed (silt sandy loam). A numerical code is developed for calculating the principal physical and mechanical parameters of road pavement. C++ is used as a programming language. A method of evaluating the shear resistance of roadbed is proposed. To calculate the load factor of roadbed, the Drucker-Prager strength criterion is used without the term responsible for the intensity of tangential stress. A T-90 tank fitted with special rubber track pads is considered to be a static load. The computations reveal the maximum vertical deflection, equal to 0.004 m, in the contact area of the tracks. In the same area, the load factor of road pavement is 9 ÷ 10, which indicates a high bearing capacity of dense-graded asphalt concrete. The analysis of shear resistance shows the presence of irreversible deformations in gravel roadbed in the contact area of the tracks, while the load factor of silt sandy loam is 3 ÷ 10.

Gene expression programming for evaluation of aggregate angularity effects on permanent deformation of asphalt mixtures

Abstract The shape of the aggregate influences the particle interlocking capabilities, thus influencing the deformation behaviour of mixes. The research paper explores the use of gene-expression programming (GEP) as an unconventional approach to predict permanent deformation of asphalt concrete with the inclusion of aggregate angularity. Data for prediction of permanent deformation of dense graded asphalt concrete was obtained through laboratory experiments. The development and analysis of the proposed GEP technique was completed by using laboratory data. The new technique for the assessment of permanent deformation strain with additional angularity factor was developed. The GEP approach concluded satisfactory outcomes of the estimation of permanent deformation when compared to regression analysis.

Study on road performances of asphalt mixtures with granulated polymer anti-rutting additive

ABSTRACTRutting has been one of the primary concerns for highway engineers in China. Granulated polymer anti-rutting additive may be an effective way to solve this problem. However, it is difficult to find previous research on the application of granulated polymer as an anti-rutting additive in different types of asphalt mixtures. This research aims to investigate the influences of the anti-rutting additive contents on road performances based on different types of asphalt mixtures, and also explores potential reasons for road performance improvement. Three types of asphalt mixtures: dense-graded asphalt concrete (DG-AC), dense-graded Superpave (DG-Superpave)，semi-open-graded asphalt macadam (SOG-AM), were included. Road performances, including high-temperature performance, low-temperature performance and moisture susceptibility, were studied at three anti-rutting additive percentages: 0.2, 0.3 and 0.4% weight of the asphalt mixture. The mixtures without the anti-rutting additive were regarded as control groups. In order to better analyse the road performance improvements, the properties of modified asphalt with 0.4% anti-rutting additive were studied, as well as the anti-rutting additive physical form in the asphalt mixture. It was found that the anti-rutting additive improved mixture’s high-temperature performance significantly while its effects on low-temperature performance were not so. It reduced low-temperature tensile strain within 12.9% range. Moisture susceptibility was improved greatly after adding 0.2% anti-rutting additive as compared to the corresponding control groups. By increasing the additive contents to 0.3 and 0.4%, the moisture susceptibility had no significant difference compared with that of the 0.2% additive content group. Road performance improvements may relate to the combined action of reinforcement and gap filling by the elongated anti-rutting additive, as well as asphalt modification within short time. When the additive content is no more than 0.3%, the materials costs of the additive-modified asphalt mixtures are less than that of SBS-modified asphalt mixtures.

Laboratory determination of hydraulic anisotropy of dense graded asphalt concrete

Dense graded asphalt concrete is widely used in roads as support structure for vehicle loads, however, is also used for hydraulic purposes in canal linings as well as faces and cores of dams. In the design stage of these constructions it is necessary to have the permeability data of the materials that will be used and, although in some cases it is sufficient to know this parameter in only one direction, in others it is necessary to have it in two directions. This research presents test results of axial permeability in constant head permeameter and the design a of radial permeability test device in asphalt concrete made for hydraulic purposes. As a result it was determined that the compaction process of asphalt concrete, applied in one direction, causes the material to have anisotropic behavior from the hydraulic point of view, resulting in anisotropy ratios 7.1 to 10.4, for the studied asphalt mixture.

Comprehensive service properties evaluation of composite grouting materials with high-performance cement paste for semi-flexible pavement

In this paper, high-performance cement pastes (i.e. h2 and h3) and pure cement paste (s) are respectively grouted into matrix asphalt mixtures (porous asphalt concrete 13, PAC-13) to service as semi-flexible pavement materials, and the comprehensive service properties of these composite grouting materials (H2, H3 and S), including mechanics feature and pavement performance are measured and compared with those of the traditional dense-graded asphalt concrete. Test results show that these composite grouting materials have similar mechanics characteristics, and H2 and H3 possess better pavement performance and durability than S. From the contribution of two-phase material (matrix asphalt mixture and grouting material) of composite grouting material, it can be concluded that both contributive efficiency and contributive rate of matrix asphalt mixture are lower than those of the grouting material. The uniaxial compressive strength of composite grouting materials approaches to that of the grouting material, which is much higher than that of asphalt mixture (matrix asphalt mixture and AC-13); while, the compression resilient modulus of composite grouting materials quite approaches to that of the asphalt mixture. To meet the requirements on moisture susceptibility of dense-graded asphalt concrete, the air void of matrix asphalt mixture should reach 21% for grouting high-performance cement pastes, and 24% for grouting pure cement paste.

Overlay Tester Results from Dense-Graded Asphalt Concrete Mixes: Accuracy in Characterizing Crack Susceptibility

Several highway agencies have either implemented or considered implementing laboratory performance tests to estimate the cracking potential of asphalt concrete (AC) mixes during the mix design process. One such popular test, the overlay tester (OT), measures the number of cycles to failure of specimens that are caused by the repeated application of deformation. The major concern about using this test as a reliable characterization of the cracking susceptibility of AC mixes, especially for dense-graded mixtures, is the variability in the specified number of cycles to failure in the performance index. The main objective of this paper is to report a means for improving the consistency of the OT test results on dense-graded AC mixes. An assessment of a specimen preparation process that can yield more consistent results was conducted. The consistency of the traditional number of cycles to failure as well as of the load–displacement response and load reduction curves was investigated by using a modified specimen preparation process. The repeatability of alternative performance indexes, such as the critical fracture energy and crack progression rate, that can be measured from the OT test was also investigated and compared with that of the index for the number of cycles to failure. This study indicated that the raw data from the OT test seemed to be repeatable if the proposed specimen preparation process was consistently followed. Alternative performance indexes that yielded an acceptable degree of repeatability may be readily implemented in the OT test to assess the cracking characteristics of AC mixes.

Predictive Models for Storage Modulus and Loss Modulus of Asphalt Mixtures

AbstractComplex modulus of an asphalt mixture constitutes two components: E′ representing the ability of the mixture to store energy (elastic behavior), and E′′ reflecting the capacity of the material to dissipate energy (viscous behavior). The main objective of this study was to develop predictive equations for the two components, E′ and E′′, to better quantify and assess the performance of conventional and modified mixtures alternate to standard laboratory testing. The dataset used in this effort encompassed 163 conventional dense graded asphalt concrete (DGAC), 13 asphalt-rubber asphalt concrete (ARAC) gap-graded, and 9 asphalt-rubber friction course (ARFC) open-graded mixes covering 5,550 data points. Aggregate gradation, binder, and volumetric property parameters were used as predictor variables. Squared-error optimization mathematical techniques were employed in developing predictive models. The statistical goodness of fit measures of E′ and E′′ predictive models were very good to excellent. Validat...

Influences by Air Voids on the Low-Temperature Cracking Property of Dense-Graded Asphalt Concrete Based on Micromechanical Modeling

This study characterized the impacts of air voids on the low-temperature cracking behavior of dense-graded asphalt concrete. Virtual low-temperature bending beam test for dense-graded asphalt concrete was built and executed by discrete element method and PFC3D (particle flow code in three dimensions). Virtual tests were applied to analyze the impacts by content, distribution, and size of air voids on the low-temperature properties of dense-graded asphalt concrete. The results revealed that higher air void content results in worse low-temperature property of dense-graded asphalt concrete, especially when the air void content exceeds the designed air content; even with the same designed air void content, different distributing condition of air voids within asphalt concrete leads to different low-temperature properties of asphalt concrete, especially when the air void content in the central-lower part of testing sample varies. Bigger size of single air void which tends to form interconnected air voids within asphalt concrete has more harmful impacts on the low-temperature properties of asphalt concrete. Thus, to achieve satisfied low-temperature properties of dense-graded asphalt concrete, it is critical to ensure the designed air void content, improve the distribution of air voids, and reduce the interconnected air voids for dense-graded asphalt concrete.

Estimation of Fatigue Life Using Resilient Moduli of Asphalt Mixtures

Abstract The objective of this study was to determine the fundamental resilient moduli (Mr) parameters of four asphalt-rubber gap-graded (AR-gap), one asphalt-rubber open-graded (AR-open), four polymer-modified gap-graded (P-gap), and two conventional dense-graded asphalt concrete (DGAC) mixes at various temperatures and frequencies using ASTM D7369-11-based standard resilient modulus test [Standard Test Method for Determining the Resilient Modulus of Bituminous Mixtures by Indirect Tension Test, ASTM International, West Conshohocken, PA, 2011, www.astm.org]. Mr tests were conducted at 15°C, 25°C, and 35°C and at 0.5, 1, 1.5, and 2 Hz on a total of 33 samples with three samples per mix. DGAC mixes had the highest Mr followed by P-gap and AR-gap, and then followed by the AR-open mixes. Mr master curves were constructed for the mixes with 25°C as a reference. Furthermore, the Mr model was developed based on the material properties of 11 mixes totaling 121 data points provided by R2adj = 0.9436 (adjusted coefficient of estimation), and Se/Sy = 0.1579 (ratio of standard error to standard deviation indicative of relative accuracy of the predictive model), depicting excellent correlation between the measured and predicted Mr. Fatigue lives of each mix type was predicted using the obtained Mr and estimated tensile strains. The fatigue lives of the modified gap-graded mixes were found to be seven times higher than the conventional mixes. A novel approach was also devised to obtain fatigue lives of conventional and modified mixtures with a reduced thickness design concept based criterion with Mr being the major input parameter. Overall, it is envisioned that the Mr parameters obtained in this study will be helpful to understand the performance characteristics of the different mixes through future laboratory-field correlations.

Preliminary study on the correlation between two-dimension surface texture and friction

Preliminary study on the correlation between two-dimension surface texture and friction