• Energy Research

Sustainability has gained as much importance as management in business. Sustainable pavement development as a business practice should involve making evaluations according to the triple bottom line in the pavement life-cycle. Despite the current approaches to evaluating the social as well as economic and environmental feasibility of pavement projects (involving highway and airport infrastructure), there has recently been a lack of consensus on a methodology to guarantee sustainability upon assessment and analysis during the pavement life-cycle. As sustainability is a complex issue, this study intends to further explore sustainability and elaborate on its meaning. The second step involves a general depiction of the major sustainability appraisal tools, namely cost-benefit analysis, life-cycle cost analysis, life-cycle assessment, multi-criteria decision-making, environmental impact assessment and social life-cycle assessment, and an explanation of their cons and pros. Subsequently, the article addresses the application of an organized methodology to highlight the main factors or concepts that should be applied in sustainable pavement development and, more specifically, in sustainable pavement management. In the final step, research recommendations toward sustainability are given. This study is aimed to assist decision-makers in pavement management to plan sustainability frameworks in accordance with probable boundaries and restrictions.

Airport pavements deteriorate with age due to the impacts of environmental factors and air traffic. There is a dearth of studies on the scheduling of airport pavement maintenance and the importance of assessing the different scheduling strategies using Life-Cycle Cost Analysis (LCCA). An analysis of the cost–benefit study of a delay in maintenance alternatives should be done to determine whether a one-year delay is beneficial. This study concerns airport pavement management systems and the significance of a delay in several maintenance and preservation strategies depending on the analysis of inputs and outputs based on data from the Rocky Mountain Metropolitan airport in Jefferson County, United States. Herein, four preventive maintenance strategies were reviewed: three of the strategies involve crack treatment, namely crack sealing, patching, and a slurry seal, while the review of surface treatment only looks at the overlay method, which is done based on two Pavement Condition Indices (PCI 90 and PCI 80), and the resulting improvement in service life. The novel integrated LCCA + LCA program, namely PAVECO, is introduced in this research to compare alternatives from perspectives that are not purely economic, by considering direct costs, indirect costs, and salvage values. Results show that a one-year delay in preventive maintenance increases the deterministic life cycle cost by 16%. Based on the sensitivity analysis of the discount rate, the total cost shows more than a 10% decrease as the discount rate increased by 1%. Additionally, the uncertainty in PCI 80 is higher than that in PCI 90. The probabilistic model provides stakeholders with the opportunity to consider the alternative which is most suited to the allocated budget. It can be concluded that, based on the simulation of the effects of maintenance activities during the pavement life-cycle, preventive maintenance should start when the roads are in good condition to prompt managers and stakeholders to analyze the costs during the life-cycle. Postponing the preventive maintenance of airport pavement could raise the cost by 50%. The maintenance of airport pavements in developing countries is still one of the main challenges of pavement management due to the maintenance only being done when it is necessary.

Light rail transit (LRT) is a sustainable transportation mode that ensures sustainable environmental, economic, and social development. Generally, the rate of public transportation usage in many parts of the world remains low compared to private vehicles. There is a need to understand passengers’ perception of public transportation service quality to enhance passenger satisfaction and increase ridership. Thus, this study used the Kuala Lumpur LRT service as a case study to investigate the effect of a passenger’s gender and age on their perception of the LRT service quality and their overall satisfaction. This survey involved 417 respondents. The outcome of factor analysis indicated that eight factors—i.e., signage, comfort, speediness, safety, ticketing service, facilities, staff service, and provision of information—influenced passenger satisfaction. The results of the Mann–Whitney U test and Kruskal–Wallis test indicated that the factors influencing passenger satisfaction significantly varied across a passenger’s gender and age. A more in-depth and comprehensive analysis using the ordered logit model and segmentation approach proved that provision of information, comfort, staff service, and facilities were critical determiners of passenger satisfaction in most segments. Safety factors and ticketing services had no impact on overall passenger satisfaction. The findings of this research could help LRT service providers, researchers, and policymakers formulate effective strategies for enhancing passenger satisfaction and increase the ridership for LRT services.

Airports play a critical role in transporting goods and passengers and supporting the growth of the world economy. Airports spend huge sums annually to maintain and improve pavement functions by expanding the runways, taxiways, and aprons, and perform routine maintenance and rehabilitation of the existing pavements. Besides the traditional direct costs, a comprehensive airport pavement management system should also consider indirect costs such as fuel, crew, passenger delay, aircraft maintenance, and loss of airport revenue when conducting a life-cycle cost analysis (LCCA). Engineers, managers, and stakeholders can make better decisions on the appropriate pavement maintenance and rehabilitation strategies by performing economic analyses of the direct and indirect costs. This study performed probabilistic and deterministic LCCA to contrast the effect of direct costs vis-a-vis indirect costs in airport pavement management. A case study found that indirect costs could contribute up to 20% of the total costs when using Portland cement concrete (PCC), hot mixed asphalt (HMA), and crack seat overlay (CSOL). Previous research did not give much attention to maintenance since the researchers believed that routine maintenance makes up only an insignificant percentage of the LCCA. However, routine maintenance of HMA and CSOL makes up 10.2% and 14.2% of the total cost. The rehabilitation cost of PCC makes up 16.3% of the total cost, and the rehabilitation cost for HMA and CSOL makes up 25.4% and 35.2% of the total cost.

Governments face numerous challenges in sustaining road network conditions. This is attributed to road authorities’ shortages of financial and physical infrastructure. As a result, low-cost automated solutions are being pursued to solve these problems and provide people with appropriate road conditions. Several attempts have been made to improve these technologies and incorporate them into a Pavement Management System (PMS) but limited attempts are made for developing countries. This study aimed to design a low-cost pavement management system for flexible pavement maintenance. A detailed literature review has been carried out, followed by a qualitative assessment of the various indicators considered for PMS. The priority ranks of the PMS indicators were made using an Analytical Network Process (ANP) and each rank was validated by a sensitivity assessment test using the Super Decision-Making tool. This paper also provides the conceptual framework for the low-cost PMS, followed by a fishbone diagram of the indicators and sub-indicators. It is concluded that an emergency maintenance plan with an ANP weight of (0.41) is one of the most significant plans for a low-cost PMS, followed by a routine with an ANP weight of (0.39) and periodic maintenance plans with a (0.20) ANP weight. Moreover, the functional indicators with an ANP weight of (0.32) are the most significant indicators for a low-cost PMS, followed by structural (0.26), safety (0.24), and serviceability(0.18) indicators. This model will assist the road planners in making better decisions on pavement maintenance management plans. The model will suggest the pavement sections on a higher priority to be added in the maintenance plans, especially where the maintenance budget is limited.

The crumb rubber (CR) recycled from waste tyres could be a viable alternative in achieving green pavements that offer exciting new markets to global investors. Adding CR into flexible pavements enhances their performance and ensures environmental sustainability. This paper will discuss the production variables, CR sizes and contents, blending techniques, optimum bitumen contents, morphology, standard characteristics, rheological characteristics, mechanical performance, greenhouse gas emissions, energy consumption and life cycle cost. This review study found that compared to traditional asphalt mixtures, the CR-modified asphalts had superior performance and longer service life. However, the dearth of information on several factors in CR asphalt production, including greenhouse gas emissions, energy consumption and life cycle cost during recycling, causes many agencies in the global asphalt industry to continue employing costly, energy-consuming additives such as styrene-butadiene-styrene (SBS) instead of CR to enhance asphalt.

The only type of conventional bitumen (PG 64-10) available in the Kingdom of Saudi Arabia (KSA) does not meet the temperature requirements of most of the kingdom’s regions. Hence, the binder needs to be modified to improve the performance of flexible pavements at high temperature and heavy traffic loading. In order to meet the requirements of the Superpave Performance Grade (PG), crumb rubber (CR), epolene (EE-2), and date palm ash (DPA) were used as asphalt additives in different percentages (4%, 8%, 12%, and 16% by weight of bitumen). Viscosity and rheological tests as well as stability and indirect tensile tests were performed on binders and asphalt mixtures. The binders modified with CR, EE-2, and DPA showed improved rheological and performance properties as compared to conventional binder. Similarly, the PG of conventional asphalt was upgraded with the addition of different percentages of the modifiers. Furthermore, this study also aimed to help the environment by minimizing and recycling wastes in road construction processes to achieve sustainability.

El pavimento de la carretera es una estructura que se expone a diversas condiciones climáticas. Para hacerlo más duradero, la modificación del aglutinante de asfalto con polímero es una opción popular. Sin embargo, para mantener la sostenibilidad ambiental, es necesario reducir la temperatura de mezcla y compactación. El aditivo Warm Mix Asphalt se había utilizado ampliamente para este propósito. En esta investigación, se investigó el impacto de un aglutinante asfáltico modificado con polímero, PG76, junto con un aditivo químico WMA, Rediset, en las aguas subterráneas y la contaminación del suelo. El efecto de Rediset en PG76 en términos de viscosidad y energía de activación también se estudió mediante la prueba de viscosidad rotacional. Aunque se encontró que Rediset podría afectar la viscosidad de PG76, la energía de activación muestra valores independientes. Se empleó ATR-FTIR para comprender la reacción entre estas dos sustancias. Se encontró que no había habido reacción química entre PG76 y Rediset. Como complemento, se utilizó AFM para observar las características de la superficie a microescala. Parece que Rediset contribuyó a la morfología de la superficie del aglutinante. Finalmente, la prueba de lixiviación del tanque modificado junto con el análisis de ICP-MS, descubrieron que después de 64 días sumergidos bajo la inundación, Rediset-PG76 no tuvo ningún efecto sobre la fuente de agua y el suelo adyacentes. La chaussée est une structure qui s'expose à diverses conditions climatiques. Pour le rendre plus durable, la modification du liant d'asphalte avec du polymère est une option populaire. Cependant, pour maintenir la durabilité environnementale, la température de mélange et de compactage doit être réduite. L'additif Warm Mix Asphalt avait été largement utilisé à cette fin. Dans cette recherche, l'impact d'un liant bitumineux modifié par un polymère, PG76, associé à un additif chimique WMA, Rediset, sur la contamination des eaux souterraines et des sols a été étudié. L'effet de Rediset sur PG76 en termes de viscosité et d'énergie d'activation a également été étudié via le test de viscosité rotationnelle. Même s'il a été constaté que Rediset pourrait affecter la viscosité de PG76, l'énergie d'activation montre des valeurs indépendantes. L'ATR-FTIR a été utilisé pour comprendre la réaction entre ces deux substances. Il a été constaté qu'il n'y avait pas eu de réaction chimique entre PG76 et Rediset. En complément, l'AFM a été utilisé pour observer les caractéristiques de surface à l'échelle microscopique. Il est apparu que Rediset a contribué à la morphologie de surface du liant. Enfin, le test de lixiviation du réservoir modifié ainsi que l'analyse par ICP-MS ont révélé qu'après 64 jours submergés sous les inondations, Rediset-PG76 n'avait aucun effet sur la source d'eau et le sol adjacents. Road pavement is a structure that expose to various climate conditions. To make it more durable, modification of asphalt binder with polymer is a popular option. However, to maintain the environmental sustainability, the mixing and compaction temperature needs to be reduced. Warm Mix Asphalt additive had been widely used for this purpose. In this research, the impact of a polymer modified asphalt binder, PG76 together with a chemical WMA additive, Rediset on groundwater and soil contamination was investigated. The effect of Rediset on PG76 in terms of viscosity and activation energy was also studied via the rotational viscosity test. Even though it was found that Rediset might affect the viscosity of PG76, the activation energy shows independent values. ATR-FTIR was employed to understand the reaction between these two substance. It was found that there had been no chemical reaction between PG76 and Rediset. As a complementary, AFM was utilised to observe the surface characteristics at micro-scale. It appeared that Rediset did contribute to the binder's surface morphology. Finally, the modified tank leaching test together with analysis by ICP-MS, discovered that after 64 days submerged under flood, Rediset-PG76 had no effect on the adjacent water source and soil. رصيف الطريق هو هيكل يعرض لمختلف الظروف المناخية. لجعله أكثر متانة، يعد تعديل المادة الرابطة للأسفلت بالبوليمر خيارًا شائعًا. ومع ذلك، للحفاظ على الاستدامة البيئية، يجب تقليل درجة حرارة الخلط والضغط. تم استخدام إضافة خليط الأسفلت الدافئ على نطاق واسع لهذا الغرض. في هذا البحث، تم التحقيق في تأثير المادة الرابطة الإسفلتية المعدلة بالبوليمر، PG76 جنبًا إلى جنب مع إضافة WMA الكيميائية، إعادة التجفيف على تلوث المياه الجوفية والتربة. كما تمت دراسة تأثير Rediset على PG76 من حيث اللزوجة وطاقة التنشيط من خلال اختبار اللزوجة الدورانية. على الرغم من العثور على أن Rediset قد تؤثر على لزوجة PG76، فإن طاقة التنشيط تظهر قيمًا مستقلة. تم استخدام ATR - FTIR لفهم التفاعل بين هاتين المادتين. وجد أنه لم يكن هناك تفاعل كيميائي بين PG76 وRediset. وكمكمل، تم استخدام AFM لمراقبة خصائص السطح على نطاق صغير. يبدو أن ريديسيت ساهم في مورفولوجيا سطح المادة الرابطة. أخيرًا، اكتشف اختبار ارتشاح الخزان المعدل جنبًا إلى جنب مع التحليل الذي أجراه ICP - MS أنه بعد 64 يومًا من الغمر تحت الفيضان، لم يكن لـ Rediset - PG76 أي تأثير على مصدر المياه والتربة المجاورة.