Hot Mix Asphalt Mixtures Research Articles

Laboratory based performance evaluation of high content reclaimed asphalt pavement in hot mix

During maintenance, rehabilitation, or reconstruction operations removing existing asphalt pavement materials are common. This practice produces a large amount of reclaimed asphalt pavement (RAP), which contains valuable asphalt binder and aggregate. The road construction and maintenance works depend on the utilization of natural and industrial materials which is limited and scarce. As existing pavement diminishes, obtaining quarry sites is difficult.The objective of this study is to conduct laboratory based- research that investigates and evaluates the performance of hot mix asphalt mixtures containing different amounts of RAP for binder course construction.Quality test for all materials used in the mix was done separately. Marshall Parameter was done for control mix and mix containing RAP to evaluate the mechanical properties of the asphalt binder mixture containing RAP and control mix. To predict the field condition performance test such as moisture susceptibility, indirect tensile strength, and Humberg wheel tracking test was conducted.The obtained result for all mixes is in terms of Marshall Parameter criteria and the performance test proves that the asphalt binder course mix can be successfully produced using RAP material within the specification limit. The study concluded that, using RAP in HMA up to 40% is possible to design a mix that satisfied the required specification for Marshall Property and performance test with low cost than the control mix.

Effect of Soft Clay on the Volumetric and Mechanical Properties of Hot Mix Asphalt

Abstract. To define the behaviour of asphalt mixture including various penetration grade bitumen has been a major subject of paving engineering. This search investigated the volumetric and mechanical properties of a hot-mix asphalt (HMA) mixture with the Superpave mix design. The mixture was added with powdered soft clay at five different percentages based on the bitumen weight (0%, 2%, 4%, 6%, and 8%). Performance tests were then conducted to determine the resilient modulus and volumetric properties of the mixture. Results show that bulk specific gravity increased after adding soft clay to the asphalt mixture. The amount of air and mineral aggregate voids also decreased with increasing SC contents. Furthermore, the addition of 4% SC improved mixture stiffness, as determined through indirect resilient modulus test under aging conditions. Therefore, soft clay can be added to asphalt mixtures to improve their volumetric and mechanical properties, such as strength and durability.

Investigating mechanical properties of hot mix asphalt containing iron ore flotation tailing

Studies involving the use of iron ore tailings from the beneficiation process in different market niches are increasingly necessary due to the large environmental damage caused by their disposal in dams, since they are waste generated in high volumes and which have low economic value for mining companies The main purpose of this study was to investigate mechanical properties of hot mix asphalt mixture containing iron ore flotation tailing. For this, a mixture containing iron ore flotation tailing and a control mixture with natural aggregates and stone dust were prepared according to the Marshall methodology and tests of stability and flow, indirect tensile strength, resilient modulus, fatigue test and dynamic creep tests were conducted. Results show that the mixture with iron ore flotation tailing had performed technically appropriate, due to the similarity of mechanical properties of the control mixture. Therefore, the results obtained revealed that the iron ore flotation tailing presented technical characteristics appropriate to its use incorporated into hot mix asphalt. In addition, their use as an alternative material in asphalt pavements can generate environmental benefits by reducing the volume of material deposition in tailings landfills and exploration areas for mineral aggregate mining.

Basic performance and asphalt smoke absorption effect of environment-friendly asphalt to improve pavement construction environment

During the high-temperature construction of hot mix asphalt mixture, a large number of harmful emissions such as asphalt smoke are produced, which seriously endangers the workers’ health and pollutes the surrounding environment. The object of this study is to reduce the emission of asphalt smoke and improve the construction environment. Tourmaline (T), graphene oxide (GO), KH 550 silane coupling agent (K) were used to prepare GO/KT-modified asphalt and the influence of modifier content on the asphalt basic performance was studied. The micromorphology and chemical constituents of the modified asphalt were analyzed, and the asphalt smoke adsorption effect of the modified asphalt was evaluated. It provides a useful reference for the green and sustainable development of road infrastructure. The results show that GO/KT composite powder can improve the asphalt basic performance. GO/KT has an excellent adsorption effect on asphalt smoke, and the emission reduction rate of GO/KT-modified asphalt can reach 41.11%. Considering the asphalt basic performance, asphalt smoke adsorption performance, and economic benefits, the recommended GO/KT and GO appropriate contents are 20 wt% and 1.0 wt%, respectively.

Foamed warm mix asphalt mixture containing crumb rubber: Foaming optimization and performance evaluation

To address global concerns of global warming, environmental pollution, and rapid urban growth associated with the development of transportation infrastructure and the increasing accumulation of waste tires, warm mix asphalt and crumb rubber modified asphalt have been proposed as green technologies for environmentally-friendly pavement. However, limited research has devoted to the behaviors of the foamed warm mix asphalt with crumb rubber (FWMA-CR). This study aims to investigating the foaming condition of the FWMA-CR binder and evaluating performance of both FWMA-CR binder and mixture. It is recommended to fabricate the FWMA-CR binder at foaming temperature of 160 °C, water content of 2.0%, and air pressure of 0.70 MPa, achieving desirable foaming characteristics of expansion ratio, half-life, and foaming index. The manufacturing temperature of the FWMA-CR mixture is remarkably dropped by 17 °C in comparison with that of the hot mix asphalt mixture with crumb rubber (HMA-CR). It has also explored that the performance of the FWMA-CR binder is consistent with that of the mixture. The foamed rubberized asphalt binder and mixture exhibit better low-temperature performance and fatigue resistance, while present inferior high-performance performance in comparison with conventional rubberized asphalt binder and mixture. The statistical analysis verifies that the foaming imposes no significant impact on performance of rubberized asphalt. The environmental and economic analysis reveals that compared to hot mix asphalt mixture with crumb rubber, the production of the FWMA-CR mixture contributes to approximate 7.4% of energy saving, 0.78 $ of cost saving, and reduction of CO2 emission by 7.2% per 1 ton of mixture. The outcomes facilitate the production and usage of the foamed warm mix asphalt with crumb rubber.

Effect of marshal and gyratory compaction methods on cracking characteristics of hot mix asphalt concrete materials under all three basic modes of fracture

Asphalt mixtures in the laboratory scale studies are often compacted and manufactured using two well-known methods namely gyratory and marshal methods. Due to differences in compaction procedure, employing any of these methods can affect the overall strength and mechanical properties (such as the fracture toughness and cracking resistance) of hot mix asphalt (HMA) materials. Understanding the effect of compaction method on cracking behavior of asphalt mixtures can provide good insights for estimating the long-term performance of pavements and roads. Therefore, in this research the effect of HMA compaction method is studied experimentally on modes I, II and III cracking behavior and fracture toughness values using the edge notch disc bend (ENDB) specimen. In addition, the effect of adding recycled asphalt pavement (RAP) material is also studied on the fracture behavior. Accordingly several HMA mixtures compacted with both marshal and gyratory methods and containing 0 and 50 % RAP material are tested at a fixed low temperature of −25 °C and the corresponding values of KIc, KIIc and KIIIc as well as the work of fracture values under all three basic modes of loading are obtained. The experimental results show the noticeable effects of loading mode, RAP content and compaction method on the fracture behavior of tested HMA materials. In general, adding RAP material reduces the fracture toughness values for all loading modes. However, compaction method has different effects on the fracture toughness values. While the KIc value obtained from gyratory compaction method is higher than the sample made of marshal method, opposite trends are seen for the shear type fracture modes (i.e. KIIc and KIIIc). The tensile mode over shear type mode fracture toughness ratios (KIIc/ KIc and KIIIc/KIc) as well as the effective fracture toughness and effective work of fracture values for the tested HMA mixtures are also presented and analyzed.

Effects of Aging on Pavement ME Predictions of Permanent Deformation for HMA and WMA Mixtures

AbstractThis paper presents an experimental investigation into the effects of aging on the rutting performance of both hot-mix asphalt (HMA) and warm-mix asphalt (WMA) mixtures and an analytical st...

Discussion of “Two-Step Mixing Process Elaboration of the Hot-Mix Asphalt Mixture Based on Surface Energy Theory” by Liping Liu, Mingchen Li, and Qingbing Lu

Discussion of “Two-Step Mixing Process Elaboration of the Hot-Mix Asphalt Mixture Based on Surface Energy Theory” by Liping Liu, Mingchen Li, and Qingbing Lu

Closure to “Two-Step Mixing Process Elaboration of the Hot-Mix Asphalt Mixture Based on Surface Energy Theory” by Liping Liu, Mingchen Li, and Qingbing Lu

Closure to “Two-Step Mixing Process Elaboration of the Hot-Mix Asphalt Mixture Based on Surface Energy Theory” by Liping Liu, Mingchen Li, and Qingbing Lu

Preparation of polyurethane solid-solid low temperature PCMs granular asphalt mixes and study of phase change temperature control behavior

In order to slow down the cooling rate of mixture and reduce the low-temperature cracking of asphalt pavement in large temperature difference areas, polyurethane solid–solid low-temperature phase change materials (PSLPCMs) were prepared by prepolymer method in this study. The PSLPCMs were incorporated into hot mix asphalt mixture to prepare PSLPCMs particle asphalt mixture. The pavement performance and phase change temperature control behavior of this special type of mixture were analyzed from the perspectives of particle content and particle size. Studies have shown that PSLPCMs have good phase change thermal storage performance and thermal stability. Different PSLPCMs content and particle size have certain improvement effect on the high temperature stability and low temperature crack resistance of the mixture, and have no obvious adverse effect on the water stability of the mixture. At the same dosage, with the increase of particle size, the improvement effect of PSLPCMs particles on the road performance of the mixture is more obvious. With the increase of PSLPCMs particle content, the specific heat capacity of asphalt mixture increases, and the thermal conductivity decreases. The temperature regulation effect of asphalt mixture shows an increasing trend, and the cooling rate slows down. The PSLPCMs particles with particle size of 1.18–2.36 mm have better improvement effect on the temperature regulation performance of the mixture. When the content of PSLPCMs is 7 wt%, the maximum temperature regulation effect of the mixture reaches 3.4 °C.

Experimental Evaluation of Moisture Damage and Rutting Resistance for SBS Modified Warm Mix Asphalt Incorporating Recycled Asphalt Concrete

The efforts embedded in this paper have been devoted to designing, preparing, and testing warm mix asphalt (WMA) mixtures and comparing their behavior against traditional hot mix asphalt mixtures. For WMA preparation, the Sasobit wax additive has been added to a 40/50 asphalt binder with a concentration of 3%. An experimental evaluation has been performed by conducting the Marshall together with volumetric properties, indirect tensile strength, and wheel tracking tests to acquire the tensile strength ratio (TSR), retained stability index (RSI), and rut depth. It was found that the gained benefit of reduction in mixing and compaction temperatures was reversely associated with a noticeable decline in Marshall properties and moisture susceptibility indices designated by TSR, and RSI, and even the rut resistance was adversely affected. Modification of WMA mixtures by 3% of Styrene-Butadiene-Styrene (SBS) polymer coupled with replacement of virgin ingredient by 50% of recycled asphalt concrete granted a 20% and 15% growth in Marshall stability and tensile strength, respectively. Moreover, both TSR and IRS indices have risen to 87% and 90%, respectively associated with a 39% increase in rutting resistance ability.

Prediction of low-temperature fracture resistance curves of unmodified and crumb rubber modified hot mix asphalt mixtures using a machine learning approach

Fracture resistance curves (R-curves) provide a robust tool for a comprehensive insight into the crack propagation regime in engineering materials. In this paper, an extensive research program is conducted to determine R-curves for hot mix asphalt (HMA) mixtures with varying properties. The experimental results are then used to develop R-curve prediction models following a machine learning approach. Three-point single-edge notched beam (SE(B)) experiments were conducted on HMA mixtures incorporating 0%, 5%, 10%, 15%, and 20% crumb rubber at low temperatures. The temperature ranged from + 5 °C to −20 °C while limestone and siliceous aggregate with two gradations were used in developing mixtures with two base bitumen having performance grades of PG58-22 and PG64-22. It was observed that as the temperature is declined to −20 °C, the stable crack growth region is significantly diminished in the R-curves, and the mixtures undergo a brittle fracture with abrupt failure of the specimen. A temperature of −15 °C could be determined where the transition from quasi-brittle to brittle fracture occurs. Mixtures fabricated incorporating 20% crumb rubber exhibited a progressively rising R-curve at the lowest test temperature (−20 °C) even in the unstable crack propagation phase, which is a desirable material characteristic. Two prediction models were developed for R-curves. Artificial neural networks (ANN) were used in the first model resulting in an R-square value of 0.965. Due to the black-box nature of the ANN, the multi-gene genetic programming approach was also applied in the prediction of the R-curves to derive a mathematical equation between the input data and the outputs. The R-square equaled 0.870 in this method. R-curves could successfully be predicted by both methods considering the negligible to fair errors.

Effect of Aging and Moisture Damage on Fatigue Cracking Properties in Asphalt Mixtures

Recently, damage to asphalt pavements in South Korea has increased because of direct and indirect factors caused by abnormal climatic changes, such as torrential rains, prolonged heatwaves in summer, and heavy snowfall in winter. Additionally, the use of medium and heavy vehicles is also a contributing factor. Therefore, an experimental procedure to study the moisture damage and fracture properties of asphalt pavements considering the recent changes in precipitation properties, deterioration of road pavement, and traffic conditions in South Korea was developed in this study. Additionally, changes in material properties according to the indoor aging process and fatigue crack resistance were evaluated for hot mix and warm mix asphalt mixtures of the same grade and different initial production and construction temperatures. To evaluate the effect of aging and moisture damage on fatigue cracking, the experimental coefficient values of the predictive model were calculated for each condition. It was observed that the material properties of hot mix asphalt mixtures changed with an increase in aging and moisture damage. The service life of the pavement was reduced by approximately 40–80% owing to moisture damage, whereas aging had a greater effect on fatigue life as the service life increased.

Mechanical and microstructural assessments of waste foundry sand in hot mix asphalt

In this paper, it was performed physical, mechanical, and microscopic analyzes on samples of industrial waste foundry sand (WFS) and hot mix asphalt mixtures (HMA) containing WFS as fine aggregate. The HMA was produced replacing 50 and 100 % of the fine aggregate (passing 4.38 mm by sieve) by WFS (by weight) with a dense gradation suitable for pavement course layers. A “control” mixture was used without WFS. The results of typical road engineering tests such as indirect tensile strength (ITS), resilient modulus (MR), modified lottman test (MLT), and four-point bending fatigue test (FTP-4) showed that asphalt mixes containing WFS have mechanical behavior that meets the required criteria to be used as a surface course layer in asphalt pavements. The WFS has physical characteristics very similar to the ones of quarry sands. Optical stereoscope and a scanning electron microscope coupled to an X-ray energy dispersive sensor (SEM/EDS) were used in this research to analyse microstructural characteristics of WFS. Results revealed that WFS has petrographic characteristics that attend usual required criteria, considering low reactivity. These tests also showed that the asphalt binder encapsulated the WFS eliminating the presence of free pathogenic substances. It is concluded that the use of WFS in HMA has technical viability and it is a sustainable alternative for road projects.

Development of an analysis tool for deterministic and probabilistic viscoelastic continuum damage approach

Pavement industry concerns have been increasing in the past decades towards fatigue cracking due to its negative impact on asphalt pavement performance. Therefore, several studies were conducted to model and characterize asphalt mixture fatigue life and number of cycles to failure (Nf) to achieve the designer’s goal ensuring the asphalt pavement serviceability, durability and to reduce the cost. Viscoelastic Continuum Damage (VECD) approach with incorporating probabilistic analysis (P-VECD) was proposed by several researchers to characterize the fatigue cracking of asphalt mixtures reliably. Although the probabilistic VECD studies attract great attention for characterizing the fatigue crack of asphalt mixtures, the VECD-Nf model random variables (RVs) are defined by using many arbitrary assumptions. Furthermore, the proposed approaches are very complicated, which added computation complexity to the VECD mode. Therefore, the prediction of asphalt mixtures’ fatigue life is needed in a reliable and simple process. This study focuses on developing a user-friendly analysis tool that determines the Nf following the VECD approach with incorporating probabilistic analysis. To achieve this goal, the proper distribution function for each RV in the VECD-Nf model is defined, a simple analysis tool is developed using MATLAB App Designer, and previous studies data for Hot-Mix Asphalt (HMA) and Fine Warm-Mix Asphalt (F-WMA) mixtures are re-analyzed using the developed P-VECD analysis tool. By using the P-VECD analysis tool, deterministic VECD analysis, probabilistic VECD analysis, and the prediction of the fatigue life of asphalt mixtures will be possible for technicians and engineers in the asphalt community.

Development of workability based approach for assessment of production temperatures of warm mix asphalt mixtures

Warm Mix Asphalt (WMA) is a sustainable technology that allows asphalt mixtures to be produced and compacted at lower temperatures in comparison to hot mix asphalt (HMA). Several concerns have been raised regarding the determination of mixing and compaction temperatures (also termed as production temperatures) for WMA mixtures. An attempt has been made through this study to comprehensively understand and explore the procedures for appropriate measurement of production temperatures of WMA mixtures. One base asphalt binder and five different warm mix additives (with varying dosages) were used in this direction. Rotational Viscometer (RV) and Dynamic Shear Rheometer (DSR) were employed to analyse the unmodified and warm mix modified asphalt binders. A workability prototype was fabricated, and a workability-based approach was proposed to systematically assess the production temperatures. Additionally, coating ability and compactability tests were carried out to validate the obtained mixing and compaction temperatures, respectively.It was found that production temperatures determined by testing asphalt binders through RV and DSR do not yield appropriate results for warm mix modified asphalt binders. Workability analysis showed that WMA mixtures, regardless of dosage and type, exhibit improved workability in comparison to the conventional HMA mixture, at all the test temperatures. Taking HMA mixture as a reference, the maximum reduction in mixing and compaction temperatures with the inclusion of WMA technologies was found to be 22 °C and 37 °C, respectively. In addition, WMA mixtures produced and compacted at reduced temperatures exhibited similar/better coating and consistent density in comparison to the conventional HMA mixture. It is concluded that the proposed workability approach for the evaluation of production temperatures of WMA mixtures is feasible and can be adopted. The output of the present study also appreciates the use of WMA for sustainable pavement construction.

PERFORMANCE INVESTIGATION OF HOT- AND WARM- ASPHALT MIXTURES MODIFIED WITH SUPERPLAST

Moisture and stripping damages are the most prevalent cause of defects of both Hot-Mix Asphalt (HMA) and Warm-Mix Asphalt (WMA). Adhesion between aggregates and bitumen is a crucial factor that affects such defects. Various methods, such as incorporating additives, have strengthened the asphalt mixture's resistance to moisture and stripping. This paper aimed to experimentally investigate the effect of including a low-cost polymer additive (Superplast) into HMA and WMA mixtures. For this goal, a 60/70 penetration grade bitumen was used. For preparing the WMA mixtures, Showax was employed with percentages of 2, 3, 4, 5, and 6% by weight of bitumen. Polymer modified mixtures (HMA and WMA) were prepared by adding 3%, 4, and 5% of Superplast by weight of the binder. Performance characterizations of the unmodified and Superplast-modified mixtures include stiffness, moisture damage resistance, and bonding. These characteristics were evaluated via Marshall, Lottman, and Double Punching tests, respectively. Results revealed that incorporating Superplast improved the adhesion between bitumen and aggregates, which ultimately led to an increase in the stiffness and moisture resistance of both HMA and WMA. Moreover, Superplast-modified WMA mixtures exhibited the best moisture and stripping resistance performance compared to Superplast-modified HMA and other unmodified mixtures.

Investigating the mechanical properties and fuel spillage resistance of semi-flexible pavement surfacing containing irradiated waste PET based grouts

Semi-flexible pavement surfacings are constructed from impregnating highly flowable cementitious grouts into the voids of open-graded asphalt wearing course layers. Semi-flexible surfacings offer superior load bearing and rutting resistance performance when compared to either conventional or polymer modified hot mix asphalts. On the other hand, when semi-flexible surfacings are used as part of a flexible pavement construction, they offer an economic alternative to concrete construction. In this laboratory investigation, the properties and performance of semi-flexible mixes containing three types of cementitious grouts (a control grout, a grout containing regular waste polyethylene terephthalate (PET) and a grout containing gamma-irradiated waste PET) were investigated and compared to the performance of a conventional hot mix asphalt (HMA). Test results showed that the properties of semi-flexible control specimens comprising 100% cementitious grout can be matched by specimens containing 2.75% regular PET as partial replacement to the cement. When gamma-irradiated PET is used, the cement replacement content can be increased to 4.75% whilst maintaining properties comparable to the control grout. It was thus argued that gamma-irradiation is a useful tool for enhancing product sustainability. The laboratory produced semi-flexible specimens were evaluated for the degree of grout impregnation, Marshall stability, indirect tensile strength, thermal expansion, moisture resistivity, and fuel resistivity. The results were compared directly to those obtained from testing conventional HMA specimens. All three semi-flexible mixtures exhibited superior performance compared to the HMA mixture in terms of Marshall stability, indirect tensile strength, resistance to moisture damage and resistance to fuel spillage.

Laboratory Research and Evaluation on Design and Application Performance of High-Performance Cold-Mix Resin.

To improve the safety of orthotropic steel bridge decks and the construction efficiency of bridge deck pavement by enhancing the performance of pavement materials, a new-generation, high-performance cold-mix resin was prepared by carrying out the combination of micro-characteristic analysis and performance test. Meanwhile, the pavement performance and fatigue performance of high-performance cold-mix resin mixtures and hot-mix epoxy saphalt mixtures as a control group were studied experimentally. The results show that different kinds of epoxy resins show bisphenol structure in essence. The curing exothermic peak temperature of the cold-mix resin increases with the heating rate. Both the specific heat capacity (△CP) of cold-mix resin and cold-mix resin asphalts exhibit a sudden change between −20 °C and 40 °C. In resin asphalt mixtures, cold-mix resin forms the network structure skeleton whereas the asphalt distributed in the form of tiny particles. The dosage of respective component has a significant effect on the tensile strength and elongation at break of cold-mix resin. Compared with hot-mix epoxy asphalt mixtures, cold-mix resin mixtures exhibit comparable water stability and high and low-temperature performance, as well as greater fatigue life.

By-products from mechanical recycling of polyolefins improve hot mix asphalt performance

Waste of polyolefin (WOPO), the sinking fraction of polyolefin recycling, is today a production waste sent to incineration. This work reports a method for the recycling of WOPO as efficient additives to produce hot mix asphalt (HMA). Physical-mechanical characteristics of HMA containing bitumen 50/70 and WOPO were compared to PE/PP mixed polyolefin (MPO) and standard HMA control specimen. Modified HMA mixtures were characterized by density, air voids, indirect tensile strength, indirect traction coefficient, Marshall stability and quotation. Atmospheric emissions for HMA containing WOPO were proven to comply within Italian legal requirements. Data acquired demonstrate that HMA containing 4 wt% of grinded WOPO by weight of asphalt binder may be efficiently employed as flexible and resistant mixture for road pavement. Environmental and economic data reported further highlight the impact of this technology, not only for asphalt producers, but also for recycling facilities, improving plastic recycling, reducing plastic incineration, waste management costs and greenhouse emissions.