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Industrial solid waste has been widely used as an alternative additive for bituminous material modification. This study aims to evaluate the basic properties and quantify the leaching potential of modified asphalt binders incorporating crumb rubber powder (CRP) from waste tires and tin slag (TS) for a local smelting company. Three percentages of CRP and TS, at 5, 10, and 15%, were considered. The conventional asphalt binder (PEN 60/70), CRP, and TS-based modified asphalt binders were analyzed for toxicity, softening point, penetration value, elastic recovery, torsional recovery (TR), and coatability index. The findings indicated that the addition of the waste materials led to no significant heavy metal content in the asphalt binder mix. Moreover, the basic and physical properties of the asphalt binders were also improved by 5, 10, and 15% of the waste, respectively. However, TS waste exhibited limited effects on all the parameters and had a 5% optimum dosage. The modified binders’ results showed that the CRP modified asphalt binders had fewer heavy metals and responded more to elastic recovery and coatability.

This paper is oriented to appraise high, intermediate, and low temperature related performance of elastomeric and plastomeric binders and mixtures in order to evaluate their characteristics at various levels of environmental and loading conditions. Artificial oxidative hardening of asphalt binders and mixes was performed in the laboratory using short- and long-term aging protocols.At the binder level, the elastomers (styrene-butadiene-styrene (SBS) and rubber) and plastomer (ethylene-vinyl acetate (EVA)) materials improved high and intermediate temperature performance indices (G*/sin(δ) and G*.sin(δ), respectively). Interestingly, the aged SBS/bitumen blend had improved low-temperature cracking resistance compared to unaged counterpart. With the progress of oxidative hardening, the plastomer based binder did not show obvious change in the low-temperature cracking susceptibility compared to elastomer-modified binder. Seemingly, in the case of plastomer/bitumen blend, the propensity to low-temperature cracking is to a great extent controlled by the corresponding base bitumen. The plastomer based mixture had improved permanent deformation performance, whereas the elastomers afforded a tangible amelioration for the vulnerability to load and non-load associated cracking. The SBS based mixture showed highest low-temperature fracture energy compared to the EVA based mixture. Despite the determinantal effect of age-hardening to low and intermediate temperature-related cracking of mixes, the results confirmed that the elastomeric materials can retard the impact of aging level on the low temperature and fatigue cracking. Comparision of results was justified by the statistical analysis in order to determine the significance of bituminous material parameters on the measured properties.

The purpose of this study is to compare the performance of rubber-modified asphalt mixtures prepared with incorporation of latex and crumb rubber. The service characteristics of the rubber-modified asphalt mixtures were evaluated using workability index and compaction energy index to determine the ease of placing, handling, and compacting of the asphalt mixture. The engineering properties of the asphalt mixtures were also evaluated in terms of indirect tensile strength (ITS), resilient modulus, permanent deformation, moisture susceptibility, and the Leutner shear test. Crumb rubber and latex were separately used as modifiers in this study. The percentage of crumb rubber and latex used were 5% and 10%, while organo silane additive was added at a rate of 0.1%, all by the weight of asphalt binder. Through the evaluation, the modified asphalt mixture required comparable energy for compaction through the assessment of compaction energy index (CEI) as compared to the control asphalt mixture. Based on the results of performance test, it can be concluded that the crumb rubber-modified asphalt mixture showed a better performance than the latex-modified asphalt mixture in terms of fracture resistance, permanent deformation, resilient modulus, shear resistance, and moisture resistance. Overall, the rubberised asphalt mixture has better engineering performance properties that can prolong the lifespan of the flexible pavement compared to the conventional asphalt mixture.

Asphalt binders are modified to address various types of distresses, especially crack-related and permanent deformation of the pavement structure. This study focuses on evaluating the effects of Gripper, a new wax additive, on the performance of natural rubber latex (NRL)-modified asphalt binders. The morphology of the modified asphalt binders was also investigated. In this study, two percentages of NRL were considered, i.e., 3% and 6% based on the weight of the asphalt binder. Penetration value, softening point, rotational viscosity, storage stability, complex modulus, phase angle, rutting potential and torsional recovery parameters were determined to analyze the base asphalt binder (60/70) and NRL-modified asphalt binders (with and without Gripper). Also, the dispersion efficiency of NRL in the asphalt binder was observed using a polarizing optical microscope. The results demonstrate that the addition of NRL improved the performance of the asphalt binder in terms of rutting and fatigue resistance. The addition of Gripper has further improved the stability and mechanical performance of modified asphalt binders. An agglomerated and globular continuous network of mixed microstructures was formed in the modified asphalt binder irrespective of aging condition. Moreover, the unaged, short-term aged and long-term aged binders prepared with the incorporation of Gripper indicate uniformly dispersed network morphology. It can therefore be concluded that the modified asphalt binders prepared with the newly introduced additive portrays better resistance toward rutting and fatigue failures.

The objective of this paper is to establish the state of knowledge on fast pyrolysis of bio-oil and bio-asphalt binder and to facilitate efforts in improving the overall performance of bio-asphalt and maximizing its road application. On the basis of reviewing the relevant literature recently, the fast pyrolysis (FasP) preparation process of bio-oil and its main properties, the preparation process of bio-asphalt and its performance and the application of bio-asphalt have been summarized. Due to the variations in raw materials, the adopted methods of FasP to prepare bio-oil could be different, and the properties of bio-oil from different sources are also different. At present, the plant-based bio-oil (mainly derived from wood waste and sawdust) has been widely used to prepare the bio-asphalt. Research on the low-temperature flexibility, high-temperature rheology, workability and other performance of biological asphalt showed that the workability and high-temperature performance of most asphalt are improved after adding bio-oil. However, the low-temperature performance is found to relatively reduce. Also, with regards to its application as a rejuvenator, bio-oil can considerably rejuvenate the aged asphalt's mixture performance. By far, most of research on bio-asphalt is still focused on the performance of bio-asphalt binder in the laboratory; its application in practical road engineering is still to be examined. This review also provides an outlook for the future, for example, establishing an integrated preparation process from bio-oil to bio-asphalt, and evaluating the properties of bio-asphalt by new standards. Keywords: Road engineering, Bio-oil, Bio-asphalt, Preparation process, Performance, Application of bio-asphalt

The performance of an asphalt mixture does not only rely on its engineering properties. Yet, the service characteristics of an asphalt mixture do play an important role on the durability of pavemen...

The physical, chemical and morphology characteristics of the ceramic source enable its waste to be a novel modifier for bitumen. This study employed the top-down approach via dry grinding in a mech...

The consistency of the ethanol foamed binders and mixtures prepared using asphalt binders foamed by the manual injection technique and laboratory foaming device were evaluated and compared in this study. The asphalt binders foamed using both methods was prepared at 120 °C, 130 °C and 140 °C. The performance of ethanol-foamed binders was evaluated in terms of rotational viscosity, expansion ratio, and low temperature cracking. Meanwhile, the performance of foamed WMA mixtures was tested using semi-circular bending (SCB), disk-shaped compact tension (DCT), and tensile strength ratio (TSR) tests. In order to conduct the TSR test, the samples were conditioned using the Moisture Induced Stress Tester (MIST) to simulate the pore pressure and scouring effects due to a tire passing over wet pavement. The foamed WMA mixtures were produced using pre-heated aggregates at 80 °C and 100 °C and foamed asphalt binders produced at 130 °C. The nano-hydrated lime was used as the filler and anti-stripping agent. Overall, the properties of ethanol-foamed binders and WMA mixtures produced via both methods are significantly comparable, except the resistance to moisture damage test result. However, the findings indicate that the ethanol-foamed WMA mixtures prepared using both techniques are having good resistance to moisture damage, based on the TSR values more than 0.8. The foamed WMA mixtures also exhibited a better resistance to cracking, as indicated by a higher tensile strength compared to the control HMA. Additionally, the WMA specimen prepared at 100 °C was less susceptible to rutting than the samples produced at 80 °C. Keywords: Warm mix asphalt, Foaming technique, Rheological, Foam quality, Mixture performance

The escalating mass of solid waste at an overwhelming sum requires a global attention to strive for efficient waste management and to outsource the ecological treatments. The asphalt pavement industry that consumes a vast scale of natural resources while contributing to thermal and greenhouse emissions is viewed as a high potential alternative for the application of solid waste as asphalt modifier and substantial waste reduction. In efforts to urge for cleaner and greener asphalt production, a growing trend towards usage of solid waste as a renewable material is paving a sustainable future for the asphalt pavement industry. The economic options of incorporating solid waste into the asphaltic mixture coupled with proven effective performances are a green and cost-effective alternative to mitigate various pavement distresses. Various options either as coarse or fine aggregates and as fillers in powder, ash, or fibre form are to stimulate further research interest to incorporate a diversified range of solid waste into the asphalt binder and asphalt mixture. Prior to incorporating solid waste into the asphaltic mixture through the selected options, prerequisite tests in addressing engineering limitations due to the unknown properties of solid waste are reviewed. The concerns on environmental impact are given heavy metals leaching possibilities into water sources are addressed by Toxicity Characterization Leaching Procedure test, to leverage further the systematic reuse of solid waste in steering towards the cleaner production of the asphalt mixture. The microcosmic traits of solid waste namely surface morphology, mineralogical composition and chemical composition are summarized based on the usage of Scanning Electron Microscope, X-Ray Diffraction, and X-Ray Fluorescence, respectively. This systematic review is an enactment and stimulus for researchers to have a general overview before incorporating solid waste into asphalt mixture. Keywords: Asphalt modifier, Waste materials, Clean production, Energy, Carbon footprint, Green pavement

The objective of this study is to characterize the foamed asphalt binders prepared using different combinations of physical and chemical foaming agents. The foamed asphalt binders were investigated using the Rotational Viscosity (RV), Dynamic Shear Rheometer (DSR) and expansion ratio tests. Asphalt binders were also evaluated after short-term and long-term aging conditions. During the asphalt binder’s foaming process, the preheated binder was formerly foamed using a physical foaming agent (either water or ethanol), followed by the addition of sodium bicarbonate (NaHCO3) to improve the bubbling and the stability of the foam. Theoretically, through this process, numerous bubbles are generated by the vaporized ethanol or water, and the gases are released by NaHCO3, which significantly increases the volume of foamed asphalt. All foamed asphalt binders were produced at the same temperature, 100 °C, to diminish the inconsistency of binder-aging conditions during the preheating process. Overall, the results indicated that ethanol has better characteristics in lowering the viscosity of asphalt binders at low temperatures and is expelled from the asphalt binder after continuous heating at temperatures higher than its boiling point (78 °C). Although the addition of NaHCO3 has slightly increased the foamed binder viscosity that may affect its workability, it substantially lowers the volatile loss of foamed binders, as well as significantly improves the expansion ratio and the resistance to rutting.

The ability of latex to notably improve the performance of asphalt pavements has established the material as a favorable modifier in asphalt systems. However, the high viscosity of latex-mo...

The complex shear modulus (G*) and phase angle (δ) are fundamental viscoelastic rheological properties used in the estimation of rutting and fatigue pavement distress in asphalt binder. In the tropical regions, rutting and fatigue cracking are major pavement distress affecting the serviceability of road infrastructure. Laboratory testing of the complex shear modulus and phase angle requires expensive and advanced equipment that is not obtainable in major laboratories within the developing countries of the region, giving rise to the need for an accurate predictive model to support quality pavement design. This research aims at developing a predictive model for the estimation of rutting and fatigue susceptive of asphalt binder at intermediate and high pavement temperatures. Asphalt rheological and ageing test was conducted on eight mixes of modified binders used to build the study database containing 1976 and 1668 data points for rutting and fatigue parameters respectively. The database was divided into training and simulation dataset. The Gaussian process regression (GPR) algorithm was used to predict the rutting and fatigue parameters using unaged and aged conditioned inputs. The proposed GPR was compared with the support vector machine (SVM), recurrent neural networks (RNN) and artificial neural network (ANN) models. Results show that the model performed better in the estimation of rutting parameter than the fatigue parameter. Further, unaged input variables show better reliability in the prediction of fatigue parameter.

Several factors affect asphalt binder and mixture characteristics. This makes pavement performance assessment a mounting task. This paper evaluates the effects of short-term aging on compactibility and volumetric properties of asphalt mixtures using the Response Surface Method (RSM). Three different binders were utilized to produce mixtures (type AC-14). Aging temperature, aging duration, and duration in a climate chamber with increased humidity and ultraviolet lighting were considered as independent variables (IV), while compactibility and volumetric properties were regarded as dependent variables (DV). The findings revealed significant impacts of aging temperature and duration on compactibility, air voids, voids in mineral aggregate, and voids filled with asphalt, while duration in the climate chamber exhibited no significant influence on the DVs. The effects of IVs on DVs varied by binder type. This was achieved through an elaborate statistical analysis. The study, finally, demonstrates the RSM&rsquo, s potential to predict changes in responses from mathematical equations&mdash, converging with the experimental observation&mdash, with excellent accuracy. Potentially, pavement contractors can use this method by replacing haulage duration and mixtures&rsquo, temperatures during paving in the developed models. It enables them to predict the pavement density and adjust pressure as well as the number of roller passes to achieve the desired requirements.

The foaming techniques implemented in Warm Mix Asphalt (WMA) have been highly recognized to aid in the production of eco-friendly asphalt mixtures. However, to a certain extent, the application of this technology is limited by its defects in moisture sensitivity and rutting resistance. Prior to this, the WMA mixtures were prepared using ethanol and ethanol-NaHCO3 foamed binders and were tested to evaluate their moisture susceptibility, rutting potential, crack resistance and thermal cracking potential. The mixture samples were prepared based on the mixture design for a 9.5 mm nominal maximum aggregate size. The designed traffic level was less than 3 million Equivalent Single-Axle Loads (ESALs). Nano-hydrated lime was incorporated during the preparation of the sample as a filler material. The foamed WMA mixtures were prepared at three different temperatures: 80 °C, 100 °C and 120 °C; meanwhile, the control Hot Mix Asphalt (HMA) sample was prepared at 155 °C and 145 °C. For the purpose of incorporating the temperature losses during the foaming process, the foamed binders were produced at a temperature higher than the production temperatures by approximately 20 °C. Overall, the results show that 1% and 3% ethanol-foamed WMA mixtures are found to have a comparable or better performance than the control HMA mixture, especially for the samples prepared at 120 °C. The addition of nano-hydrated lime contributed to the increase on the adhesive and cohesive characteristic of mixtures; hence, improving the resistance to moisture damage. Regardless of the contents of the foaming agent and production temperatures, most of the foamed WMA mixtures prepared using a combination of foaming agents have comparable thermal cracking characteristics as the control HMA mixture. The resistance to rutting of foamed WMA mixtures increased with the increase in the production temperatures. The sample prepared at 120 °C is found to have much lower or comparable rut depths to the control HMA mixture. However, the combination of ethanol with 1% NaHCO3 was optimal for these foamed WMA mixtures prepared at 80 °C to obtain a good long-term performance.

The fracture properties of an asphalt mixture specimen can be different due to variation in raw material characteristic, mixture design, method of the mixture production, and environmental conditions. This paper summarized the fracture properties of the semicircular specimens analyzed using different methods. Loose asphalt mixtures from two asphalt mixing plants were collected and used for the sample preparation. Each mixture was unique with respect to variation in terms of binder type, binder content, aggregate gradation, filler type, and the types of asphalt mixing plants (drum or batch plant) which were used for the production of particular mixtures. The samples were tested using semicircular bending test, and compared in terms of maximum force, deformation at maximum force, stiffness, strain at maximum force, maximum stress at failure, fracture toughness, and fracture energy. The results indicated that samples produced using stiffer binders exhibited a higher resistance to fracture while consuming less energy to reach failure compared to those prepared using softer binder. In addition, this study proposed three indicators, including the velocity of fracture initiation (υFI), velocity of crack growth (υCG), and fragility index (FI) to gain a better understanding of the fracture behavior of asphalt mixtures with respect to the mixtures’ crack resistance and its propagation. The results of υFI and υCG were highly dependent on mixtures brittleness, while FI exhibited an acceptable capability to differentiate mixtures crack potential regardless of their inherent characteristics.

This paper evaluates the fracture properties of mixtures subjected to different short-term ageing conditions obtained from semi-circular bending test. Response Surface Method (RSM) was used to deve...

Asphalt binders and mixtures are more susceptible to permanent deformation at high temperature. The Dynamic Shear Rheometer (DSR) test results have been extensively used to evaluate the effects of wax and foamed warm additives on asphalt binder properties at elevated temperature. Wax based additives improve the rheological properties of the binders at high temperatures, while foamed based additives exhibit no significant effects on binder rheology. However, the literature reports contradictory effects of surfactant-wax warm additive named Rediset, on binders and mixtures propertiesat high temperatures. Some studies reported positive effects, while others found otherwise. This paper evaluates the effects of binder type, additive content and loading type on high temperature properties of warm asphalt binders incorporating Rediset on temperature, strain, frequency and stress sweep tests as well as flow, creep, multiple stress creep and recovery and zero shear viscosity test results. The results showed that the effects of Rediset depended on binder type, additive content and loading type. It implies that the chemical composition of different dosage of this warm additive with various binder types, directly affect the performance of binders subjected to various loading types at high temperatures. Hence, simply relying on one type of shear loading in the DSR test for evaluating the high temperature properties of binders incorporating a surfactant-wax additive, can lead to erroneous conclusions.

The microstructure characteristic of asphalt mixture has substantial effects on its macroscopic mechanical properties. The study on the structural characteristics of asphalt mixtures involving the microscopic scale has rarely been considered. This study investigates the effects of the angularity of coarse aggregate on the microstructure of two commonly practiced asphalt mixture gradations (AC-16 and SMA-16) based on the X-ray Computed Tomography (XCT). Three-dimensional angularity was introduced based on the XCT images. Four indicators including average contact point number (ACN), average contact length (ACL), average vertical contact index (AVCI) and average horizontal contact index (AHCI) were proposed to evaluate the skeleton contact characteristics within the asphalt mixture through iPas. The volume of air voids, equivalent diameter and roundness were used to characterize the void characteristic of the asphalt mixtures with different angular aggregates by the analysis of Image-Pro Plus (IPP). The results indicate that the three-dimensional angularity (3DA) could characterize the angularity of coarse aggregate. The angularity has a significant influence on the skeleton contact characteristics of asphalt mixture, whereas a lower angularity has resulted in weaker skeleton contact characteristics. A skeleton contact characteristic of SMA-16, with a dense coarse aggregate structure, is stronger than AC-16, which belongs to the dense suspension structure. The shape of the voids at the top and bottom of the asphalt mixture specimen is the most complex and irregular, while the shape of air voids in the middle section of the specimen is simple and regular. This study could provide support for the further research and application of microscopic properties of asphalt mixtures.

In this study, the effect of fly ash (FA) as an alternative filler mineral was evaluated regarding workability, structural performance, durability, and its sustainability when prepared using hot (HMA) and warm mix asphalt (WMA) technologies. The results revealed that workability of HMA and WMA samples containing FA are comparable to the mixes containing cement powder, yet the WMA mixes containing 4% Sasobit® prepared at 145 °C exhibited the highest workability, regardless of filler type. However, the compaction energy index (CEI) of WMA samples containing FA is more sensitive to the Sasobit® content variations at each mixing temperature. Besides, use of FA as an alternative filler mineral increased the resilient modulus up to 7.5% as compared to HMA and WMA containing cement powder. The tensile strength ratios of asphalt mixtures containing FA are not only satisfied the design criteria, but it is also higher than those of samples with cement filler. Use of WMA technology improves sustainability in the construction phase, while incorporation of FA filler decreases the greenhouse gas emissions during the raw material manufacturing stage. Therefore, synergistic effects of using the WMA technology and FA improve the sustainability of both construction and raw material processing within the cradle to gate phases. In conclusion, a higher workability and resilient modulus test result together with less environmental emission indicate that the WMA technology using Sasobit® and FA as an alternative filler are showing great potential for the production of eco-friendly asphalt pavement.

This paper presents an alternative method for developing a laboratory short-term ageing procedure for binders that corresponds to the asphalt mixture production practices carried out in a tropical region. In this method, the ASTM D2872 procedure was adapted to artificially short-term age asphalt binders, while ageing time and ageing temperature were evaluated. A statistical technique named response surface method (RSM) was used for the design of experiment, analysis of the test results from the field and laboratory samples, and selection of an appropriate laboratory protocol. An experimental matrix was designed based on the central composite method for two basic independent laboratory factors: ageing times in a range of 85–175 min, and ageing temperatures within 148–178 °C. Several test variables, include softening point, penetration, G∗/sin δ at 64 °C and rotational viscosity at 135 °C of three conventional binders were considered as dependent test factors (responses). The responses were analyzed using RSM to derive mathematical equations, while the corresponding time and temperature were determined from optimization of the test results. The outcome of this study indicated that the conventional short-term ageing protocol in accordance with the ASTM D2872 may not be sufficient to simulate the short-term ageing of asphalt binders in the Malaysian weather condition, where high daily temperatures, humidity, and ultraviolet are concerned. Based on the statistical analyses, both time and temperature have significantly affect the physical and rheological properties of short-term aged binders. Overall, all three binders show quadratic models for the resulting responses with the exception of two binders which show 2FI and linear models for its physical properties. The resulting optimization recommends a short-term ageing procedure at 170 °C for 135 min to appropriately mimic the field binder properties under Malaysian climate.

The experimental investigation of the effects of filler-bitumen interaction on the stiffening and shearing characteristics of asphalt mastic is presented in this paper. The role of filler particles in terms of particle dispersion, particle sedimentation rate, particle dissipation energy, and their shearing response as a function of their viscosities under different concentrations was analysed. Structural and geometrical morphological tests of the filler particles were also carried out using the Scanning Electron Microscope (SEM) analysis. A neat bitumen of 60/70 penetration grade and two alternative mineral fillers, namely lime kiln dust (LKD) and dolomite powder (DP), were used to produce asphalt mastic mixture at a filler- bitumen ratio (F/B) of 0.4, 0.8, and 1.2 in accordance with the Superpave mix design dust to binder ratio specification. The two individual fillers particle size gradations, was assessed using a laser diffraction technique. The delta ring and ball, as well as the penetration index tests were conducted to determine the physical properties of the asphalt mastic. The shearing response of the asphalt mastic was also determined using a rotational viscometer (RV) device for various shear values at mastic mixing temperature. The results of the study inferred that the stiffening ability of mineral fillers was more dependent on the physical filler properties, such as particle surface area, voids between the interstices of particles, the concentration of particles, and the crowding distance of the particles in the asphalt mastic. It also revealed that the resistance of a neat bitumen to shearing occurs in a shear-thinning response behaviour, while that of an asphalt mastic occurs more as a shear thickening resistance response. The morphological analysis of both the fillers highlighted the differences in voids, fines, surface area, and particle shape structure of the two fillers.

Asphalt foaming techniques have been used over the last couple of decades as an alternative to the traditional method of preparing asphalt mixtures. Various efforts have been initiated to assess the technology and enhance its efficiency during production. In this article, a comprehensive review of foaming warm mix asphalt (WMA) techniques, foaming theory and mechanisms, research and development as well as characterization procedures are presented. This paper also summarized numerous research and paving applications using foaming WMA technologies in Europe, the United States, Canada, China, Australia, New Zealand and some other countries. Findings from laboratory tests and field performance are also presented. Based on several field trials, the performance of foaming WMA is comparable to conventional HMA. The United States was found to be the most active country working on research-based and field trial evaluations on WMA besides two European countries: Germany and Norway. In addition to reducing energy consumption, reductions in fuel usage have significantly reduced the stack emissions of greenhouse gases, such as carbon dioxide, sulfur dioxide, and nitrous oxide. This review concludes with some recommendations in terms of diversifying the foaming agent and selection of test parameters in order to have a better precision and repeatability of test results.

Applications of foamed binder have been spurred by the increased focus on sustainable construction approach and stringent environmental laws. This study was initiated to evaluate the performance of foamed asphalt binder produced using a combination of physical and chemical foaming agents, known as ethanol and sodium bicarbonate (NaHCO 3 ), respectively. This paper presents the properties of foamed asphalt binder assessed using Fourier transform infra-red (FTIR) spectroscopy, asphalt binder cracking device (ABCD), and activation energy analysis. The FTIR test was conducted to evaluate the possibility of any chemical reaction taken place, as well as to characterize the effects of oxidation on the chemical functional groups present in foamed asphalt binders. The ABCD test was carried out to evaluate the thermal cracking temperatures of prepared binders. The activation energy of each binder type was analyzed based on the viscosity test results and Arrhenius equation to estimate the energy required to overcome the intermolecular forces between the molecules in the asphalt binder to initiate flow. The FTIR results reveal that ethanol alone is unreactive with the binder, where most of the functional groups have shown comparable change ratios. This indicates that there are no chemical reactions that occurred in the foamed asphalt binders, either with the addition of ethanol or various combinations of ethanol and NaHCO 3 . The application of foaming agents definitely lowers the activation energy to overcome the intermolecular forces between the molecules in the asphalt binder to allow flow to occur. The foamed binders were found to have a comparable or better low temperature characteristic as compared to the control binder. A higher dosage of foaming agents proportionally increased the resistance to thermal cracking of asphalt binders. Overall, the use of foaming technique and newly proposed foaming agents has shown great potential to produce eco-friendly pavement material.

While crumb rubber (CR) can improve the performance of asphalt pavement in several aspects, it has a noticeable concern of higher emission and increased energy consumption due to a higher production temperature. This study made a comprehensive evaluation of the environmental and mechanical performance of the CR modified warm mix asphalt with Evotherm third generation. The CR modified hot mix asphalt (HMA) and control HMA were also investigated for a comparative study. Moreover, both the laboratory compacted samples and the field collected samples were studied. The environmental performance includes the neat asphalt savings, fuel savings and hazard emission reduction. The mechanical performance evaluated included tensile strength and moisture susceptibility, rutting resistance, anti-stripping performance, fatigue performance, and low temperature performance. The neat asphalt saving with CR was found to be 5.8% compared to unmodified asphalt. The fuel savings in this study was around 13%, and a visible hazard emission reduction was observed as well. The mechanical performance results showed that the CR-WMA with Evotherm had equivalent rutting resistance and low temperature performance and better fatigue performance and moisture damage resistance compared to the CR-HMA. The CR-WMA with Evotherm and CR-HMA had a higher tensile strength and better low temperature performance than the control HMA. In regard to the comparison between the CR-WMA and CR-HMA, the laboratory compacted and field collected samples were consistent overall. The results also indicated that the moisture damage resistance evaluated through the tensile strength ratio and the HWT may not perfectly agree with each other.

Recently, numerous warm mix additives were developed and their influences on the properties of asphalt binders and mixtures were investigated in the field and laboratory. Although, most of the technical requirements for these materials have been accepted for individual conditions, some important questions still remain unfolds. For instance, which combinations of production parameters are referred to fabrication of an optimum product? This study presents a new potential approach to answer this question via a numerical optimization for all test responses using desirability functions. For this purpose, a surfactant-wax warm additive was used for modification of binders. A series of warm mix asphalts (WMA) specimens were fabricated using a polymer modified binder, in different compaction temperatures, additive contents and binder contents. Experiment design was planned and analysis was conducted by a statistical approach named response surface method (RSM). The price of raw materials, mechanical properties of mixtures and energy consumption for production of WMA were involved in the analysis of data. This method presented an optimum combination of decision factors including binder contents, additive contents and compaction temperatures to produce one ton WMA in different production scenarios. Although, there are different recommendations for use of additive contents, optimization process proposed 1% of additive for modification of binder for various scenarios. Possibility for simultaneous determination of binder content in combination with other factors could discard the process of traditional Marshall method to ascertain the optimum binder content.

The property of asphalt binder plays an important role in the performance of asphalt mixture. The natural rubber additive (NRA) was recommended as a modifier in the preparation of high viscosity asphalt (HVA) binder. Then, the gradation named LASTIKA-13 was adopted to design the high viscosity asphalt mixture (HVAM) according to the orthogonal test analysis and the optimized gradation. The performance of the proposed HVAM was evaluated through a series tests including the permanent deformation at high temperature, moisture stability, low-temperature cracks, and bending fatigue test. The results indicate that the proposed modified asphalt binder shows a comparable property with the conventional modified asphalt binder. The proposed HVAM with the NRA modifier has a superior performance to other conventional mixtures in the temperature susceptibility and resistance to moisture damage. Furthermore, the proposed HVAM was less sensitive to the temperature change and has good performance in terms of resistance to low-temperature cracks, bonding characteristics, and fatigue behaviors.

Conventional asphalt binder is widely used as the crack sealing material. Crack sealing is one of the most frequent pavement maintenance methods. The level of performance during service life has a close relationship with the properties of asphalt binder used in the pavement or as crack sealant material. As for the pavement crack mechanism, there are two different working mechanisms that occur within the pavement crack, which is horizontal and vertical movement. Horizontal movements are caused by shrinkage and expansion of pavement due to the thermal changes in pavement material. While, the moisture related changes causes vertical movement. This study aims to introduce an alternative testing protocol that can simulate the real failure mechanism of pavement crack. This is due to limited approaches that had been taken by previous researchers to evaluate the performance of pavement-crack sealant. The tensile strength and resistance to shear stress had been chosen as the main performance evaluations in pavement crack sealant material. Prior to that, the bond test and Layer Parallel Direct Shear Test had been used to evaluate the tensile strength and shear resistance of crack sealant material, respectively. This testing protocols could be adopted by other researchers for further studies and also by the asphalt industry.

The microscopic spreadability and storage stability of conventional asphalt binder (PEN 60/70) and 6% natural rubber latex (NRL) modified asphalt binder (with and without the incorporation of surfactant) were investigated in this study. The prepared samples were assessed under both unaged and short-term ageing (RTFO-aged) conditions. Subsequently, the storage stability was conducted on all asphalt binder samples under conditioning condition designated at 180 °C for 72 h. Optical and polarising microscopes were used to observe the surface morphology of asphalt binders. The results revealed that for 6% NRL modified asphalt binder under unaged condition, the formation of globular agglomerated microstructures can be detected. However, the NRL modified asphalt binder that is subjected to RTFO-ageing with the incorporation of different additives yielded homogeneous and interconnected structures with lamellar orientation. This is due to the evaporation and absorption effects, which could have improved the rutting and fatigue resistance of asphalt binders. The storage stability results exhibited similar microstructures with little or no observable morphological differences. Overall, the incorporation of surfactants improved the miscibility, homogeneity, and stability of latex modified asphalt binder.

In the field, the workability and compactability of asphalt mixtures are essential to obtain the desired smoothness and sufficient density of a compacted pavement, especially for the asphal...

This research aims to evaluate the behavioural interface-bonding response of modified asphalt binders towards different types of additives. In this study, 6% natural rubber latex (NRL) was added into a conventional asphalt binder (PEN 60/70) with the subsequent addition of 0.1% silane additive and 0.3% Gripper (wax based) additive, based on the weight of the asphalt binder. The chemical functional groups and the effects of oxidation on the specimens were determined from attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The contact angle and surface free energy of the asphalt binders were measured using a goniometer device and analysed using the DROP image Advanced Software. Results from this study showed that the rubberised asphalt binders, with or without additive incorporation, possessed improved resistance to oxidation due to increases in CH and OH functional group concentrations, as well as improved wettability rate. In addition, the NRL modified asphalt binder with additive incorporation exhibited outstanding performance compared with PEN 60/70 and NRL modified asphalt binder without additive. Both additive incorporations showcased comparable performances, but with the Gripper additive incorporation having a better performance at different ageing conditions. Overall, the additive addition as surfactant showcased the potentiality to improve the interfacial bonding behaviour of NRL modified asphalt binders with aggregate, hence improving resistance to permanent deformation and fatigue cracking.

Mortar creep takes place when the asphalt mortar continuously migrates downwards due to gravitational forces and can significantly disrupt air voids continuity in porous asphalt samples. This study was an extension to a previous work that ascertained the existence of the binder creep phenomenon as reflected from the continual permeability loss especially on samples conditioned at elevated temperatures. Nonetheless, in this paper, the terminology “mortar creep” was adopted instead of “binder creep”. This is because, in an asphalt mixture, the aggregates are glued together not by the binder in isolation, but by the mortar; which is comprised of asphalt binder, fine aggregates and filler. The variables investigated included aggregate gradation, binder type, bitumen content and conditioning temperature. The mixes were prepared using conventional bitumen (60/70 pen. grade) and modified asphalt binder (PG76) at three levels of binder content at 0.5% increment. Permeability loss was continuously monitored over an extended period up to 120 days using a simple falling head water permeameter. Over the test period, the samples were separately conditioned at 15 °C, 20 °C, 30 °C and 35 °C. The results showed that all factors significantly affect the occurrence of mortar creep in porous asphalt prepared in the laboratory, especially for the specimens conditioned at the highest temperature. Permeability loss was more significant on specimens’ prepared using conventional binder at a higher bitumen content.

This study evaluated the performance of e-waste modified asphalt binders. E-waste modifiers Acrylonitrile Butadiene Styrene (ABS), Acrylonitrile Butadiene Styrene-Polycarbonate (ABS-PC) and High Impact Polystyrene (HIPS) were used after 100% of the material passed through a #50 (300 μm) sieve. A conventional asphalt binder, PG58-28 binder, was used as a control. The e-wastes were blended with the control binder as untreated (UT) and chemically treated (T) modified binders. Chemically treated (T) modifiers were processed with cumene hydroperoxide before blending into PG58-28, to promote covalent molecular bonding between the e-waste plastic and asphalt. Results showed that untreated e-waste modified asphalt binders were stiffer and more elastic behavior than the control binder, but when these same e-waste plastics were first treated with cumene hydroperoxide, the increases were significantly higher. Use of chemically treated e-waste modifiers also significantly improves the resistance to rutting of asphalt binders, as shown by the work dissipated per loading based on the analysis conducted at 1.59 Hz. The improved results are attributed to the cumene hydroperoxide promoting direct covalent molecular bonding between e-waste plastic powders and the asphalt binder. These results suggest that when polymer modifiers are used in asphalt, radical reactions, at least at the interface with the modifier, should be promoted rather than prevented by added radical inhibitors.

This project integrates recent innovations of recycled materials used in designing and building sustainable pavements. An increasing environmental awareness and the demand for improving economic and construction efficiencies, through measures such as construction warrantees and goals to reduce air pollution under the Kyoto Protocol, have increased the efforts to implement sustainable materials in roadways. The objective of this research is to develop a systematic approach toward selecting optimum combinations of sustainable materials for the construction of asphalt pavements. The selected materials, warm mix asphalt (WMA), recycled asphalt shingles (RAS), and reclaimed asphalt pavement (RAP) were incorporated in this study. The results of this research are intended to serve as guidelines in the selection of the mixed sustainable materials for asphalt pavements. The approach developed from this project draws upon previous research efforts integrating graphical modeling with optimizing the amount of sustainable materials based on the performance. With regard to moisture susceptibility and rutting potential test results, as well as the MIM analysis based on a 95% confidence interval, the rutting performance and moisture susceptibility of asphalt mixtures are not significantly different regardless of the percentages of RAS, RAP, or WMA. The optimum mixture choices could be made by the plant emission rankings with consideration of the optimal WMA types, percentages of RAS/RAP, and WMA production temperatures. The WMA mixtures prepared with 75% RAP and Advera® WMA have produced the lowest CO2 emissions among the investigated mixture types.

The modification of asphalt mixtures using latex has gained popularity in the asphalt industry as it improves the durability of road pavement. However, the elastomeric properties of latex stiffen the binder, resulting in more energy consumption during the asphalt mixture production. It would consequently cause a higher emission of greenhouse gases, which is undesirable for the human health and environment. This study aims to assess the applicability of diluted methanol as a foaming agent in asphalt mixture incorporating latex produced at a lower temperature. In this study, two designated amounts of diluted methanol (1% and 3% of the weight of asphalt binder) were successively injected with 6% latex into pre-heated asphalt binder at 135 °C in the preparation of foamed binders, while the control and latex modified asphalt mixtures were prepared at 160 °C. Tests of rotational viscosity, expansion rate, and torsional recovery were conducted to study the rheological properties of the mixtures. Service characteristics were evaluated through the indices of workability, compaction energy, and coatability. Moreover, mixture performance tests were carried out to identify the tolerance of the mixtures towards moisture damage, shear force, and permanent deformation. Through the rotational viscosity test, diluted methanol was found to reduce the viscosity of the asphalt binders, which is vital in the production processes at intermediate temperatures. The enhancement in viscosity using 3% diluted methanol had facilitated in higher workability, lower compaction energy, and better aggregate coating, which are the crucial criteria for a better mixing and compaction process. Whereby, a superior foaming quality was exhibited from the 3% diluted methanol application through the assessments of expansion ratio, half-life and foaming index. The moisture and shear resistances of the diluted methanol foamed asphalt mixtures are comparable to the control mixtures even though they were prepared at a lower temperature. Finally, the 3% diluted methanol foamed asphalt mixture promoted a better rutting resistance due to its ability to recover to the initial form which was demonstrated through its torsional recovery.

As a developing nation that moves towards the sustainability, initiatives had been taken to address the solid waste disposal problem by incorporating them into asphalt pavement construction. This study integrates the recycled material named Recycled Paper Mill Sludge (RPMS) into the production of asphalt mixture as modifier through the partial substitution of mineral filler. The usage of solid waste material in pavement construction could substantially reduce the waste production and reduces the possibility of those waste materials ending up on landfills. This paper evaluates the microscopic analysis such as XRD, XRF and the mechanical properties of asphalt mixture with the incorporation of Recycled Paper Mill Sludge (RPMS). Mechanical properties that were evaluated were indirect tensile strength (ITS), moisture sensitivity, resilient modulus, Leutner shear and dynamic creep. RPMS was added to the asphalt mixture through dry process at the rate of 0.5% and 1%. Addition of RPMS at specific rate improved the mechanical properties such as resilient modulus, Leutner shear and dynamic creep of asphalt mixture. The lapped antenna like fibre of RPMS improved the resilient modulus of asphalt mixture by acting as a reinforcing material. Furthermore, RPMS contains calcite compounds that promote the adhesion bonding between asphalt binder and aggregates which significantly improved the performance in Leutner shear test and dynamic creep test.

The objective of this study is to investigate the rheological properties, bonding and resistancetoshear of the rubberized modified binders under different conditions. A base asphalt binder with penetration grade 60/70 was utilised in this study. The crumb rubber and natural rubber latex were added at different percentages for the modified bitumen production, and computed based on the mass of bitumen. Silane additives at the rate of 0.1% by mass of asphalt binder were used as a surfactant. A series of rheological properties and recovery test were conducted on all binders. While bond test and Layer-Parallel Direct Shear (LPDS) test were carried out in order to simulate the crack movement of pavement. The results show that the addition of crumb rubber and latex positively impacts the performance of the asphalt binder. The crumb rubber and natural rubber latex modified asphalt binder has comparatively identical elastic recovery outcomes, while it also helps in enhancing the stiffness in terms of softening and penetration value. However, natural rubber latex modified asphalt binder performed much better than crumb rubber modified asphalt binder in terms of torsional recovery. Whereas, rotational viscosity test has been useful in adopting the suitable temperature which is 160 °C in order to satisfy the needs of better workability and to ensure it is pumpable. Storage stability test proved that the modified asphalt binders are homogenous since the temperature differences are less than 5 °C. The dynamic shear rheometer (DSR) test proved that the modified asphalt binder has better resistance to rutting. Through DSR findings and activation energy, the modified asphalt binder were catogorize as less susceptible to temperature changes. Finally, the crumb rubber modified asphalt binder did well in terms of bonding strength, while the natural rubber latex modified asphalt binder performed well in terms of resistance to shear. Overall, both rubberized modified binders performed better than the control sample.

The demand for bituminous materials is continuously growing, crude oil-based asphalt binders are non-renewable, and are facing rapid depletion. With the increase of petroleum-based asphalt prices, seeking an alternative, renewable material such as bio-asphalt has become a hot research topic. However, shortcomings in this research area have been identified, notably concerning the high-temperature performance of bio-asphalt at present. This research aims to comprehensively apply conventional tests to, and study the rheological behavior of, the high-temperature performances of bio-asphalt binders, i.e., by temperature and frequency sweeps, using a dynamic shear rheometer (DSR). It will also assess the chemical functional groups of specimens prepared by different aging conditions. Fifty penetration grade base asphalt binder (50#), bio-oil modified asphalt binders with 0%, 5%, 10%, and 30% bio-oil contents by mass, and bio-oil modified asphalt binder with combinations of 5% bio-oil-1% SBS, and 10% bio-oil-1% SBS were used in this study. The conventional performance of bio-asphalt binders was tested using penetration, ductility, and softening point, before and after short-term aging conditioning. The temperature sweep and frequency sweep of bio-asphalt under different bio-oil contents were carried out via DSR. Two-logarithmic equations of rutting factor and temperature were established, and the temperature sensitivity of bio-asphalt was analyzed. The master curves of virgin asphalt and bio-asphalt were constructed at 64 &deg, C. The results indicate that the incorporation of bio-oil reduced the anti-rutting performance of asphalt, and the bio-oil content had a significant effect on the mass loss of the bio-asphalt binder. The performance of bio-oil modified asphalt binders using 5% bio-oil, 5% bio-oil-1% SBS, and 10% bio-oil-1% SBS, could meet the requirements of 50# grade asphalt. The temperature sensitivity of bio-asphalt did not show obvious change before and after short-term aging, whereas the temperature sensitivity of bio-asphalt with 5% bio-oil was relatively small. With an increase in temperature, the phase angle increased gradually. In contrast, the storage modulus, loss modulus, and complex modulus decreased progressively. The complex modulus and rutting factor of bio-asphalt with 5% bio-oil steadily increased with the increase in testing frequency. Otherwise, chemical reactions were detected in the 50# base asphalt modified with the bio-oil.

One of the major concerns with WMA is degradation due to the presence of moisture during production. In the field, moisture in the aggregates may not be completely expelled due to a lower production temperature which increases the potential for moisture damage, including stripping. The objectives of this paper are: (1) to investigate the impact of hydrated lime on the moisture resistance of WMA mixtures prepared using saturated surface dried (SSD) moist aggregates; (2) to examine the effects of multiple freeze–thaw cycles on the moisture susceptibility of WMA mixtures. Testing samples were prepared in the laboratory with the materials from a local asphalt plant in Michigan according to the Superpave mix design. The control samples (HMA) were mixed and compacted at 165 °C and 155 °C, respectively. The WMA samples were prepared using different additives, which were Advera, Sasobit, Cecabase RT, and water as a foaming agent. For the moisture susceptibility evaluation, the mixtures were prepared using SSD aggregates and the WMA mixtures were both mixed and compacted at a similar temperature, 130 °C. Hydrated lime was added as an anti-stripping agent to determine whether or not it can improve the moisture susceptibility of the HMA and WMA prepared using SSD moist aggregate. The samples for the multiple freeze–thaw study were prepared according to a similar mix design at numerous temperatures (100 °C, 115 °C and 130 °C) and different percentages of WMA additives based on the specific ranges recommended by the manufacturer of each WMA technology. Each additive was added to the asphalt binder prior to mixing with aggregate based on the designated percentage. Based on the results, the presence of hydrated lime in the WMA has resulted in the TSR values passing the minimum requirement of 0.80. This indicates that by adding hydrated lime, the moisture susceptibility of the WMA can be improved. The WMA samples that were tested under multiple freeze–thaw cycles do not perform as well as the HMA samples. Different additives perform better at different quantities in the mixture, as well as at different temperatures. Lower mixing and compaction temperatures negatively affect the TSR after repeated freeze–thaw conditions.

This study aims to characterize the rate of change that takes place in the rheological properties of asphalt binders modified with numerous types and contents of nano-materials. The effects of nano-materials on the activation energy of modified asphalt binders under the viscous and visco-elastic behavior were also investigated. Through the research findings, the application of non-dimensional analyses using relative viscosity and relative G ∗ /sin δ (NSRP) are very meaningful to evaluate the rate of change in the rheological properties of asphalt binder per one unit percent of nano-material. It is also found that the non-dimensional viscosity index (∇ η ) and non-dimensional Superpave™ rutting factor gradient (∇NSRP) are influenced by the type and content of nano-material, and test temperature. The activation energy analysis has confirmed that the changes in amount of energy consumed are not only influenced by the type and content of nano-material, but also the physical phase of the modified asphalt binders.