Effectiveness of heat-reflective asphalt pavements in mitigating urban heat islands: A systematic literature review

Urban heat island(UHI) effect is a growing concern in numerous cities worldwide, which increases urban temperatures. Conventional asphalt pavements are a major contributor to the issue, causing environmental and health concerns. To tackle this issue, the implementation of cool pavements such as heat-reflective asphalt pavements has been introduced. This systematic literature review(SLR) thoroughly examines prior research to assess the effectiveness of heat-reflective asphalt pavements in reducing UHI effects. This SLR was conducted in accordance with the preferred reporting items for systematic review and meta-analysis(PRISMA) guidelines to enhance data reliability and minimize bias. This review process involved establishing review protocol, formulating review questions, systematically selecting articles through identification, screening, eligibility, quality appraisal, and data abstraction and analysis from various databases such as Scopus, Web of Science(WoS), Wiley, Taylor Francis, and Science Direct. Three primary themes and nine sub-themes were derived from the three review questions. From the results, heat-reflective asphalt pavements effectively minimized the UHI effect. However, their efficiency varies depending on factors such as pavement types, paving location, and use of cool materials. A comprehensive analysis examined heat-reflective pavement's mechanisms, benefits, and drawbacks. This investigation aimed to enhance comprehension and establish a robust basis for future studies in this field.

Experimental assessments of methanol-based foaming agent in latex modified foamed binders and warm asphalt mixtures

Latex is one of the natural rubbers that is used to enhance the performance of asphalt pavement for the last few decades.The presence of latex,which is categorized as an elastomer,helps to improve pavement performance and durability.Conversely,higher viscosity of latex modified asphalt binder increases the production-temperatures of asphalt mixture,thus consuming higher energy during asphalt mixture’s production stage.In this study,the effectiveness of methanol as an energy-efficient foaming agent was assessed to reduce the viscosity and enhance the workability of the modified asphalt binder.The basic and rheological properties of the asphalt binders were determined through multiple laboratory tests including expansion ratio and half-life,rotational viscosity,softening point,torsional recovery,and dynamic shear rheometer.The properties of asphalt mixtures were assessed through the service characteristics,mechanical performance,and moisture resistance criteria.It was found that the presence of latex results in an approximately twofold higher expansion ratio and a lower half-life of the asphalt binder at about the same ratio.Through the rotational viscosity test,the application of methanol into asphalt binder decreased the viscosity and led to better workability,despite the addition of latex as an asphalt modifier.The application of methanol into asphalt binder improved the workability of mixture samples and lowered the compaction energy of the compaction process,which are the crucial criteria for a better mixing and compaction process.Methanol foamed asphalt mixtures with latex show much higher resistance to moisture damage and stiffness than control sample even though they were prepared at a lower temperature.

Rheological and MECHANICAL Performance of Asphalt Binders and Mixtures Incorporating CaCO3 and LLDPE

This study was conducted to assess the performance of modified asphalt binders and engineering properties of mixtures prepared with incorporation 3 vol%and 6 vol%of calcium carbonate(CaCO3),linear low-density polyethylene(LLDPE),and combinations of CaCO3 and LLDPE.The rheological properties of control and modified asphalt binders were evaluated using a series of testing such as rotational viscometer(RV),multiple stress creep recovery(MSCR)and bending beam rheometer(BBR)tests.Meanwhile,four-point beam fatigue test,the dynamic modulus(E*)test and tensile strength ratio(TSR)test were conducted to assess the engineering properties of asphalt mixtures.Based on the findings,the RV and MSCR test result shows that all modified asphalt binders have improved performance in comparison to the neat asphalt binders in terms of higher viscosity and improved permanent deformation resistance.A higher amount of CaCO3 and LLDPE have led modified asphalt binders to better recovery percentage,except the asphalt binders modified using a combination of CaCO3 and LLDPE.However,the inclusion of LLDPE into asphalt binder has lowered the thermal cracking resistance.The incorporation of CaCO3 in asphalt mixtures was found beneficial,especially in improving the ability to resist fatigue cracking of asphalt mixture.In contrast,asphalt mixtures show better moisture sensitivity through the addition of LLDPE.The addition of LLDPE has significantly enhanced the indirect tensile strength values and tensile strength ratio of asphalt mixtures.

Analytical study of silane-based and wax-based additives on the interfacial bonding characteristics between natural rubber modified binder and different aggregate types

The modification of asphalt binder with natural rubber latex(NR)significantly improves the rutting and fatigue resistance of asphalt mixtures.However,NR-modified binder is prone to low workability and wettability due to its high viscosity.Therefore,this research focuses on examining the influences of silane and wax-based additives on the wettability of natural rubber-modified binders and the binder-aggregates adhesion performances.In this study,experimental and analytical approaches were used.The contact angles of asphalt binder were measured using a goniometer through the sessile drop method with three solvents:deionised water,formamide,and glycerol.The Cþþalgorithm was adopted to compute the surface free energy(SFE)elements of the asphalt binder.Analytical methods were employed to analyse the results based on the Young-Dupre equation,followed by linear regression to establish a correlation between the compatibility ratio(CR)and the SFE components.The results inferred that modified asphalt binders with additives possessed improved moisture resistance,wherein dry work adhesion values were less than 210 mJ/m^(2)under granite interfaces,whereas the limestone interface exhibited higher dry adhesion values of 340 mJ/m^(2)and below.Similar performance results were observed under wet adhesion conditions;with granite wet adhesive values observed below 120 mJ/m^(2),while limestone wet adhesion values were ascertained below 180 mJ/m^(2)for all tested samples and conditions.According to the spread–ability coefficient results,the limestone interface has greater spread-ability than granite interfaces.Meanwhile,compatibility ratio values indicated better compatibility of 1.9 or higher for tested samples under granite interfaces,whereas compatibility values of 1.7 and below were observed under limestone interfaces.

Rheological and physicochemical characteristics of asphalt mastics incorporating lime kiln dust and dolomite powder as sustainable fillers

The filler-bitumen interaction mechanism is one of the most essential phases for comprehending the asphalt mixture's performance.However,despite numerous studies,in-depth knowledge of filler-bitumen reciprocity at a microscale level is yet to be ascertained.The goal of this research is to gain a better understanding of the fillerbitumen microscale interaction in terms of the synergy and coaction between the physicochemical and rheological performance of mastics due to filler inclusions.The rheological properties of two sustainable mastics,dolomite powder(DP)and lime kiln dust(LKD),together with a neat PEN 60/70 binder,were analysed based on a temperature sweep at elevated temperature conditions.Meanwhile,frequency sweep and multiple stress creep recovery(MSCR)tests were also conducted at pavement serviceability temperature using the dynamic shear rheometer(DSR).Physicochemical tests using a scanning electron microscope(SEM)and energy dispersive X-rays(EDX)were conducted to analyse the impact of parameters such as particle shape,grain size,texture,and chemical compositions.The DSR test results showcased how the incorporation of fillers in asphalt binder considerably improved the performance of the binder in terms of rutting and fatigue.Likewise,its strain and nonrecoverable compliance parameters were substantially reduced at higher filler and binder concentrations.Physical filler attributes of low rigden voids(R.V),high fineness modulus(FM),and high specific surface area(SSA)led to greater interfacial stiffness and elasticity in LKD mastics compared to DP mastics at different loading frequencies and temperature levels.The SEM/EDX results also indicated that the elemental calcium and carbon composition of each filler component,together with its grain morphology,strongly influenced its rheological performance.

Preparation process of bio-oil and bio-asphalt,their performance,and the application of bio-asphalt:A comprehensive review

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 perform ance of bioasphalt 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 bioasphalt by new standards.

Review of sustainability, pretreatment, and engineering considerations of asphalt modifiers from the industrial solid wastes

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.

Research and applications of artificial neural network in pavement engineering:A state-of-the-art review

Given the great advancements in soft computing and data science,artificial neural network(ANN)has been explored and applied to handle complicated problems in the field of pavement engineering.This study conducted a state-of-the-art review for surveying the recent progress of ANN application at different stages of pavement engineering,including pavement design,construction,inspection and monitoring,and maintenance.This study focused on the papers published over the last three decades,especially the studies conducted since 2013.Through literature retrieval,a total of 683 papers in this field were identified,among which 143 papers were selected for an in-depth review.The ANN architectures used in these studies mainly included multi-layer perceptron neural network(MLPNN),convolutional neural network(CNN)and recurrent neural network(RNN)for processing one-dimensional data,two-dimensional data and time-series data.CNN-based pavement health inspection and monitoring attracted the largest research interest due to its potential to replace human labor.While ANN has been proved to be an effective tool for pavement material design,cost analysis,defect detection and maintenance planning,it is facing huge challenges in terms of data collection,parameter optimization,model transferability and low-cost data annotation.More attention should be paid to bring multidisciplinary techniques into pavement engineering to tackle existing challenges and widen future opportunities.

Recent development,utilization,treatment and performance of solid wastes additives in asphaltic concrete worldwide:A review

Asphalt modifications either involved commercial or recycled waste materials modifiers help optimise and improve the deficient properties of asphalt mixtures relative to current standards.This manuscript reviews the recycling of waste materials generated from various sources such as household,agricultural and industrial to minimise natural resources exploitation,lower energy demand,and enhance overall pavement performance.The actual development and implementation of recycled asphalt pavement in numerous countries in Asia,North America,South America,Europe and Africa are emphasised,and their influence on the performance of asphalt pavements is reviewed.Modified pavement showed satisfying performance for years as maintenance and restoration are not required.Generally,solid wastes are required to undergo pre-requisite treatments via mechanical,biological stabilization,thermal or chemical methods before the implementation as asphalt modifiers to ease the handling process.Moisture damage issues have been spotted in the implementation of several types of solid wastes and consequently reduced the strength and durability of pavement.Therefore,potential hydrophobic treatment can be adopted to improve the quality of asphalt mixtures by modifying the hydrophilic characteristics that are contributed by the hydroxyl groups on the cellulose nanocrystals(CNCs)or providing a superhydrophobic coating onto the particles.The treatments greatly weakened the moisture sensitivity of modified materials by reducing their water absorption and increasing their water contact angle.The modified mixtures are necessary to have identical or enhanced pavement performance to the conventional mixtures.Besides,future researchers are encouraged to broaden the research field in pavement engineering by considering chemical treatments in improving material properties to achieve cost-saving,efficient waste management,and higher commercial feasibility.Before implementing any virgin materials,waste materials and by-products as alternative substances or modifiers,it is strongly advised to consider the environmental and economic impacts of the material properties and their optimal incorporation.

Comparative study of ethanol foamed asphalt binders and mixtures prepared via manual injection and laboratory foaming device

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℃, 130℃ and 140℃. 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℃ and 100℃ and foamed asphalt binders produced at 130℃. 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℃ was less susceptible to rutting than the samples produced at 80℃.

Effects of diluted methanol and water as foaming agents on the performance of latex foamed warm asphalt mixtures

Latex as an asphalt modifier has gained popularity in the asphalt industry as it improves the durability of asphalt pavement.However,the elastomeric properties of latex stiffen the asphalt binders,resulting in additional energy consumption during the production of asphalt mixtures,which may cause a higher emission of greenhouse gases.This is undesirable for sustainable development and the environment.In this study,the applicability of diluted methanol and water was comparatively evaluated as foaming agents in the production of warm mix asphalt(WMA)mixtures incorporating latex.Diluted methanol was used because it has a lower boiling point and latent heat than water,allowing the asphalt mixture to be produced at a lower temperature and thus consuming less energy.The performance of the foamed asphalt mixture was investigated through service characteristics,mechanical performance,and moisture susceptibility of mixtures.The service characteristics,on the other hand,were measured in a laboratory while preparing and compacting the asphalt mixture,which refers to the amount of energy required during the production and construction stages in the asphalt plant and on the construction site,respectively.The degree of energy required was assessed based on the workability index,coatability index,and the compaction energy index.The mechanical performance of asphalt mixtures was characterized by indirect tensile strength,resilient modulus,and dynamic creep tests.The resistance to moisture damage was evaluated based on the common parameter,indirect tensile strength ratio.The findings revealed that the use of diluted methanol foaming agent helped improve the workability of latex modified asphalt mixtures.The foamed latex-modified WMA demonstrated better performance compared to asphalt mixtures prepared using water as the foaming agent.

Ethanol based foamed asphalt as potential alternative for low emission asphalt technology

Foamed asphalt typically relies on water as a foaming agent because water becomes gaseous at elevated temperatures, generating numerous tiny bubbles in the asphalt and causing spontaneous foaming. In this study, ethanol was used as a potential alternative to water as a foaming agent. Ethanol is expected to be a physical blowing agent in the same manner as water, except it requires less energy to foam due to its 78 ℃ boiling point. This study compares the performance of water and ethanol as foaming agents through the measurements of rotational viscosity, the reduction in temperature during foaming, and volatile loss. The ethanol-foamed asphalt binders were prepared at 80 ~C and 100 ~C, while the water-foamed asphalt binders were prepared at 100 ~C and 120 ~＇C. Additionally, the rolling thin film oven （RTFO） was used to generate short-term aging of the foamed asphalt binders. A rotational viscometer was used to determine the viscosity of the asphalt binders at 80 ~C, 100 ~C, 120 ~C, 140 ~C, and 160 ~C. Overall, ethanol can function in the same manner as water but requires less energy to foam. It is proven based on the smaller drop in temperature of the asphalt binder foamed using ethanol compared with that prepared with water. This is due to the lower latent heat capacity of ethanol, which requires less energy to vaporize compared with water. Through the rotational viscometer test, ethanol performs better in lowering the viscosity of asphalt binders, which is essential in allowing produc- tion processes at low temperatures, as well as a better workability and aggregate coating. Ethanol can be expelled from the foamed asphalt binders at a higher rate due to its lower boiling point and latent heat.

A hybrid strategy in selecting diverse combinations of innovative sustainable materials for asphalt pavements

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 con- struction 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）I and reclaimed asphalt pave- ment {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 pave- ments. 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 re- suits, as well as the MIM analysis based on a 95% confidence interval, the rutting perfor- mance 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, per- centages 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.