Modelling the long-term sustainability impacts of coordination policies for urban infrastructure rehabilitation

Due to structural and hydraulic deterioration, urban water pipe networks have annual rehabilitation needs. Worldwide, these needs are often significantly larger than the actual amount of rehabilitation being performed, leading to increased risks of serious failures, lower performance and a growing techno-financial burden for future generations. It is well accepted that, in order to limit the multiple impacts of utility works in the urban environment, rehabilitation projects should be coordinated between water, transport, energy and telecommunication infrastructures. In practice, such coordination means that public utilities must rehabilitate assets earlier or later than technically needed, in order to engage in joint projects in which digging and resurfacing expenditures are shared. Hence, at the municipal scale, such coordination influences two variables that are key to strategic decision support: average costs (€/metre) for asset rehabilitation, and the service lifetimes of those assets. However, current models for strategic asset management do not enable practitioners to estimate how changes in the coordination process may influence the long-term financial and environmental impacts of infrastructure rehabilitation. The present study aimed at addressing this methodological gap by introducing the concept of a coordination window that quantifies to what extent utilities compromise asset rehabilitation times in order to join multi-utility projects. An algorithm for modelling the influence of the coordination window size on long-term sustainability costs is presented and applied to one Swedish municipality. The results suggested that total capital costs and carbon emissions can be lowered by 34% and 16% with a coordination window of 35 and 25 year, in comparison to the no-coordination case.

PFAS contaminated asphalt and concrete - Knowledge gaps for future research and management

Per- and polyfluoroalkyl substances (PFAS) are now widespread in the environment. Globally, airfields and paved firefighting training surfaces are particularly affected due to extensive use of aqueous film forming foams (AFFF). This PFAS contamination in exposed concrete and asphalt has not been widely addressed. This review focusses on PFAS interaction with concrete and asphalt, traversing extraction, analytical identification/quantification, PFAS fractionation via differential adsorption on organic and inorganic substrates, and reuse options for contaminated concrete and asphalt. A total of 24 knowledge gaps and management challenges for concrete and asphalt characterisation and management have been identified.

A bibliometric analysis of rejuvenators in reclaimed asphalt pavement

This study looked at the state-of-the-art present knowledge base and trends in the area of using rejuvenators in reclaimed asphalt pavement (RAP) by systemic analysis and visualisation using VOSviewer and Scopus analyser; a total of 1872 studies were mined from the Scopus database for the purpose of this study. This quantitative approach to the review of literature removes author bias. The study was able to identify keywords and their cluster groups making up of core research domains ((1) asphalt binder composition and properties, (2) reclaimed asphalt mixtures (recycling), (3) reclaimed asphalt performance characteristics, (4) reclaimed asphalt sustainability, (5) rejuvenating agents and their performance, and (6) area of application). The study was able to identify the top authors; their document counts and citations; the most influential journals, institutions, and countries leading the way in the research domain; and the link between these authors and keywords within the existing body of literature in the research area. This study will help policymakers in identifying the main research themes and possible area of investments for further research in RAP. This study will also be a valuable compendium to researchers who intend to broaden the scope of the research area.

Research trends on ash stabilization in the pavement during 2002-2021

Incineration ash stabilization in the pavement is an effective approach to reduce environmental impact and proper disposal. This study aimed to achieve a bibliometric analysis of "ash stabilization in pavement" research during 2002-2021, considering language, chronological trends, source types, subject areas, document types, affiliations, journals, countries, and author keywords. Also, social network analysis (SNA) was used for trends mapping and global collaboration determination among countries. The results exposed that the number of publications has been significantly increased by more than 14-fold over the studied period. Engineering (42%), material science (17%), and environmental science (10%) were three major subject areas. The USA, by 383 publications, was the leading country, followed by India (370) and China (288). The most independent rate of the publications belonged to India (93%), while Australia ranked 1st in cooperator publications (63.4%). The "Construction and Building Materials" published the most related articles, followed by "Journal of Materials in Civil Engineering" and "Road Materials and Pavement Design." Among the top ten productive institutes and organizations, four affiliations were from China, and three institutes were from the USA. Edil, T.B. (34) from the USA, Arulrajah, A. (29) from Australia, and Horpibulsuk, S. (24) from Thailand were the most productive authors. "Fly ash," "compressive strength," "durability," "geopolymer," "strength," and "resilient modulus" had the most growth rate in recent years, based on the author keywords analysis. Besides, the increase of emerging keywords, "pervious concrete," "reclaimed asphalt pavement," and "lateritic soil" are noteworthy in the second half period.

Reusing COVID-19 disposable nitrile gloves to improve the mechanical properties of expansive clay subgrade: An innovative medical waste solution

The COVID-19 pandemic not only poses an unprecedented threat to global health but also severely disrupts the natural environment and ecosystems. Mitigating the adverse impacts of plastic-based personal protective equipment (PPE) waste requires the cooperation of professionals from various fields. This paper discusses a novel, cleaner approach to soil stabilisation by repurposing the nitrile gloves into a sustainable road material to improve the mechanical properties of expansive clay soil as pavement subgrade. For the first time, extensive geotechnical testings, including standard compaction, unconfined compressive strength (UCS), unsoaked California bearing ratio (CBR), repeated load triaxial (RLT), and swelling-shrinkage tests, were carried out to investigate the engineering performance of different proportions of the shredded nitrile gloves (SNG) (e.g., 1%, 1.5%, 2%) were blended with expansive clay (EC). In addition, surface roughness, scanning electron microscopy (SEM), and X-ray micro-CT analyses were conducted, and images were obtained to study the microstructural modification of the EC-SNG mixtures. The experimental results indicated that the blend of expansive clay with SNG helped in increasing the compressive strength, resilient modulus, and CBR and assisted in reducing the swelling and shrinkage of the soil. SEM and surface roughness analyses indicated the interaction between the soil matrix interface and the rough surface of the SNG. The main reasons for increasing the strength and stability of clay soil could be attributed to the high tensile strength of the SNG and the formation of the three-dimensional grid, and friction between the soil particles and SNG. According to the X-ray micro-CT test results, the incorporation of SNG led to an increase in closed porosity.

Review of the impact of stormwater and leaching from pavements on the environment

The intensive growth of roadway infrastructure worldwide leads to growing concerns over the health impacts of stormwater runoff and leachate from roadway materials. This comprehensive review combines various sources of information from the last 30 years of research on the impact of pavement stormwater runoff and leaching on the environment. Of the 95 papers found in library searches, 42 papers add significantly to the body of literature around this subject after review of content and quality. Normally constructed asphalt and concrete pavements were found to release low levels of contaminants during their life. However, deposition from atmospheric pollutants and materials dispersed by vehicles on pavements do have a measurable impact on the quality of stormwater runoff. These tend to be expressed in initial flush from stormwater events. Reuse of old pavements at end of life tend to have little environmental impact when recycled. However, because of deposition of pollutants over their life these materials can have an impact when used in unbound layers of the pavement or in storage before reuse. Water quality can be improved by porous pavements, which allow infiltration of water and drainage to lower layers, thereby filtering many pollutants in stormwater runoff. The challenge is preventing the high initial pavement porosity from plugging over time. Pavement sealers containing coal tar pitch have high levels of polycyclic aromatic compounds and have been shown to impact aquatic life negatively and produce sediment buildup in ponds and streams. Recent studies have investigated photooxidation of pavements and its influence on leaching, but these remain as laboratory-scale studies. Tables outline materials tested, analytical parameters measured, and methodologies to allow readers to easily identify studies most relevant to their focus on impact of stormwater and leaching from pavements on the environment.

A review on design, evaluation, and performance of emulsified asphalt-treated bases using recycled aggregates

Cold recycling techniques emerged in road construction to recycle deteriorated pavements as bases and surfaces. A detailed review is carried out in the current study on the design, evaluation, performance, and advances in the emulsified asphalt-treated bases (EATB). The mix-design of EATB is a complex procedure in which the performance is based on optimizing water, additives, and emulsified asphalt contents. This paper covers the design methods, compaction characteristics, curing periods, additive contents, strength development, strength parameters, determination of the optimum emulsified asphalt content, and finally, the performance evaluation of EATB. From the detailed review, indirect tensile strength (ITS) is the most influencing parameter considered in the mix design of the EATB. Maximum dry density, Marshall Stability, and ITS are considered as primary performance indicators of the EATB. Modulus, rutting, and fatigue being consider secondary performance indicators. Overall, the recycled bases using emulsified asphalt proved sustainable and economical compared with the natural aggregates (NA).

Application of coal fly ash in pavement subgrade stabilisation: A review

Expansive clays are found in many countries worldwide, and they exhibit inherent volume change during the seasonal moisture variation causing cracks, heaves, and damages to the overlying pavements. Chemical stabilisation is one of the most used approaches to treat the expansive clay subgrades. Cement, Lime and Fly ash are the most commonly used stabilisers, in which fly is cheaper and a by-product obtained from the coal power plant. This paper reviews fly ash stabilisation on various clay types, including low plasticity clays, high plasticity clays, silty clays, organic clays, and peats. The review begins with the properties of fly ash, followed by the characteristics of fly ash stabilised subgrades. The micro-level mechanism, physical, mechanical, and hydraulic characteristics of stabilised pavements are presented graphically for the Class C, and F fly ashes. The micro-level studies reveal that the pozzolanic reaction is stronger than the cation exchange during the fly ash stabilisation. The unconfined compressive strength (UCS), California bearing ratio (CBR) and resilient modulus (M_r) increased with the fly ash addition and curing time for most soft soils except peat clays. Based on the mechanical and hydraulic characteristics, using 15% class C fly ash with 7 days of curing is recommended for optimum performance. Although few research studies confirm that the leachate limit of stabilised soil is within the acceptable limit, further studies are required to investigate the uptake of heavy metals and other certain carcinogenic contaminants. This study will provide key information for researchers and Engineers on the selection of fly ash stabilisation measures for expansive subgrades.

Environment-friendly recycled asphalt pavement design for road maintenance applications

Potholes are one of the most common road distresses in Kuwait especially after winter season in 2018. Pavement deterioration rate significantly increases as the pavement exposes to moisture. Paving road requires using high-quality materials. This paper aims to investigate the feasibility of using recycled asphalt pavement in hot mix asphalt (HMA) design. Questionnaires and a series of laboratory tests were conducted to analyze the effects of pores on the society and test the recycled and the regular mixtures performance to choose the best option regarding it. Marshal test portrayed that the recycled mixture has a high stability and flow. According to the tensile strength ratio test requirements which set a minimum ratio of 75%, it is recommended to reduce the proportion of recycled aggregate. The Hamburg wheel tracker (HWTD) test proved that the recycled asphalt mixture has a low rutting depth for wet and dry samples compared to the general one. On the other hand, the wet recycled mixture requires a reduction by of 20% to satisfy the specifications. The physical properties for both mixtures were compared, and the voids filled with asphalt (VFA) and voids in mineral aggregate (VMA) of the recycled mixture are lower than those in the regular mixture. The recycled mixture reveals a higher efficiency in saving costs and improving mixtures used for potholes maintenance activities. All the results proved that the mixtures consisting of recycled asphalt are most preferred since they are affordable and perform reasonably well compared to mixtures made of regular asphalt. As a future work, smaller percentages of recycled aggregate should be tested to check the robustness and sustainability of the designed recycled asphalt mixture using different tests such as Hamburg wheel tracker test (wet samples) and indirect tensile strength test. Furthermore, more experiments can be run to test other mix parameters and properties such as durability.

Effect of eco-friendly pervious concrete with amorphous metallic fiber on evaporative cooling performance

Impervious pavements exist in large proportions in most cities owing to the high-impact development of the transportation infrastructure. However, this type of pavement causes environmental issues such as waterlogging, floods, and urban heat islands. Pervious concrete (PC), which is a novel pavement material characterized by a porous structure that allows water to percolate through it, is an important solution to these issues. This study investigates the evaporative cooling performance of eco-friendly PC with blast-furnace slag (BFS) as a cement replacement and amorphous metallic fiber (AMF) that helps to accelerate the evaporative cooling. The thermophysical properties, water permeability, and water absorption capability of the manufactured PC were measured. In addition, a scale model test and thermal conductivity analysis of the manufactured PC were conducted to evaluate the evaporative cooling effect. The results indicate that the physical and mechanical properties of the manufactured PC are typically similar to those of other PCs, and its water absorption rate reaches 1 mm/s. Relatively low water permeability helps the PCs to absorb more water, contributing to accumulate a large amount of water in the material for evaporative cooling. In addition, AMF contributes to increase thermal conductivity of PC, which allow the water inside the PCs to evaporate faster. The result shows that a higher thermal conductivity of the manufactured PC increases the evaporative cooling effect.

Data on the engineering properties of aluminum dross as a filler in asphalt

Pavement is the backbone of an effective and efficient transportation system. Data on the use of aluminium dross as filler material in the modification of asphalt for a sustainable pavement was espoused. Aluminium dross which is a solid waste from steel production industry was utilized. Data on the engineering and stability properties of the material in enhancing the strength of the asphalt mix design was espoused. This was achieved by adding the solid waste at 0%, 2.5%, 5%, 7.5%, 10% and 12.5% of aluminium dross to the asphalt concrete sample. Marshall Test was used to determine the stability of aluminium dross in flexible pavement and this was used for the selection of asphalt binder content with a suitable density which satisfies minimum stability and range of flow values using AASHTO specification. The data obtained will be of help to researchers, engineers, road construction workers and environmentalist on the use of this solid waste in the construction of sustainable long-lasting roads for national growth and solid waste reduction.

"Streets of Fire" revisited: contact burns

Background

Pavement-street contact burns are rare. This study compared recent contact burns to those published in “Pavement temperature and burns: Streets of Fire” in 1995. The hypothesis was that there were a significantly increased number of pavement-street burns, as a result of increased ambient temperatures, and that motor vehicle crash (MVC) contact burns were less severe than pavements-street burns.

Methods

This was a retrospective burn center registry study of naturally heated surface contact burns during May to September from 2016 to 2018. Statistical analyses were performed with one-way analysis of variance (ANOVA) and Maximum Likelihood chi-squared for age, percent of total burn surface area (% TBSA), treatment, hospitalization, comorbidities, hospital charges, mortality, ambient, and surface temperatures (pavement, asphalt, rocks).

Results

In the 1995 study, median ambient temperatures were 106 (range 100–113) °F compared to the 108 (range 86–119) °F highest noon temperature in the current study. No ambient temperature differences were recorded on days with pavement burn admissions compared to days without these admissions. There were 225 pavement, 27 MVC, 15 road rash, and 103 other contact burns. The major injuries in the pavement group were due to being “down” (unknown reason), falls, and barefoot. Compared to the others, the pavement group was older, 56+ years, p < 0.001, and had smaller burns but similar length of stay. Fifty percent of the 225 pavement group patients with full-thickness burns required skin grafts. There were 13 (6%) fatalities in the pavement group vs 1 (4%) in the MVC group, p = 0.01. Fatalities were secondary to sepsis, shock, cardiac, respiratory, or kidney complications. Compared to survivors, the non-survivors had a significantly higher % TBSA (10% vs 4%), p = 0.01, and lower Glasgow Coma Scores (10 vs 15), p = 0.002.

Conclusion

There was a median 2 °F increase in ambient temperature since 1995. The increase in pavement burn admissions was multi-factorial: higher temperatures, population, and the number of older patients, with increased metropolis expansion, outreach, and urban heat indices. Pavement group was similar to the MVC group except for significantly older age and increased mortality. Morbidity associated with age contributed to increased mortality.

Reduced zinc leaching from scrap tire during pavement applications

Large quantities of scrap tires have been generated and accumulated over the years. However, a significant amount of them are stocked due to the lack of environmentally-friendly methods for disposing of, or reusing them. Because tires contain approximately 1-2% zinc by weight, leaching of zinc from scrap tires could be an environmental concern. In this research, we investigated the leaching of zinc from tire particles that are used with asphalt for pavement applications. The effects of tire particle size and pH on zinc leaching were also examined. Our results indicated that asphalt treatment significantly reduced zinc leaching from tires, and that it was also reduced by increasing the tire particle size and pH. The leaching of zinc was quantified by using a speciation-based modeling approach. The model parameters, namely, the total leachable zinc mass and the adsorption constant, can be used to predict the leaching of zinc under different conditions. The reduction in zinc leaching from asphalt-treated tire particles was due to the physical blocking of the tire surface by the asphalt. Results also indicated that, while the leaching of zinc and other selected toxic elements from untreated tire particles using simulated acid rain was not significant compared to the drinking water regulations, asphalt treatment during the pavement application further improved the environmental performance of the tire particles.

Effect of fly ash on properties of crushed brick and reclaimed asphalt in pavement base/subbase applications

Fly Ash (FA), an abundant by-product with no carbon footprint, is a potential stabilizer for enhancing the physical and geotechnical properties of pavement aggregates. In this research, FA was used in different ratios to stabilize crushed brick (CB) and reclaimed asphalt pavement (RAP) for pavement base/subbase applications. The FA stabilization of CB and RAP was targeted to improve the strength and durability of these recycled materials for pavement base/subbase applications. The Unconfined Compressive Strength (UCS) and resilient modulus (M_R) development of the stabilized CB and RAP aggregates was studied under room temperature and at an elevated temperatures of 40°C, and results compared with unbound CB and RAP. Analysis of atomic silica content showed that when the amount of silica and alumina crystalline was increased, the soil structure matrix deteriorated, resulting in strength reduction. The results of UCS and M_R testing of FA stabilized CB and RAP aggregates indicated that FA was a viable binder for the stabilization of recycled CB and RAP. CB and RAP stabilized with 15% FA showed the highest UCS results at both room temperature and at 40°C. Higher temperature curing was also found to result in higher strengths.

Greenhouse gas emissions of alternative pavement designs: framework development and illustrative application

Pavement rehabilitation is carbon intensive and the choice of pavement type is a critical factor in controlling greenhouse gas (GHG) emissions. The existing body of knowledge is not able to support decision-making on pavement choice due to a lack of consensus on the system boundaries, the functional units and the estimation periods. Excessive data requirements further inhibit the generalization of the existing methodologies for design evaluation at the early planning stage. This study proposes a practical life-cycle GHG estimation approach, which is arguably effective to benchmark pavement emissions given project bid tabulation. A set of case studies conducted for this study suggest that recycled asphalt pavement (e.g., foam stabilized base (FSB), and warm mix asphalt (WMA)) would prevent up to 50% of GHGs from the initial construction phase. However, from a life-cycle perspective, pavement emissions are dictated largely by the traffic characteristics and the analysis period for the use phase. The benefits from using recycled materials (e.g., FSB) are likely to diminish if the recycled products do not perform as well as those properly proportioned with less recycled materials, or if the recycled materials are locally unavailable. When the AADT reaches 10,000, use phase releases more than 97% of the life cycle emissions and the emissions difference among alternative designs will be within 1%.