Plastic Roads in Asia: Current Implementations and Should It Be Considered?

The rapid economic and industrial growth experienced in the Asian region has significantly increased waste production, particularly single-use plastic. This surge in waste poses a significant challenge for these countries' municipal solid waste management systems. Consequently, there is a pressing need for progressive and effective solutions to address the plastic waste issue. One promising initiative involves utilizing used plastic to produce components for asphalt pavement. The concept of plastic road technology has gained traction in Asia, with 32 countries displaying varying levels of interest, ranging from small-scale laboratory experiments to large-scale construction projects. However, as a relatively new technology, plastic road implementation requires continuous and comprehensive environmental and health risk assessments to ascertain its viability as a reliable green technology. This review paper presents the current findings and potential implementation of plastic-modified asphalt in Asian countries, with particular attention given to its environmental and human health impacts. While plastic asphalt roads hold promise in waste reduction, improved asphalt properties, and cost savings, it is imperative to thoroughly consider the environmental and health impacts, quality control measures, recycling limitations, and long-term performance of this road construction material. Further research and evaluation are needed to fully understand the viability and sustainability of plastic asphalt roads. This will enable a comprehensive assessment of its potential benefits and drawbacks, aiding in developing robust guidelines and standards for its implementation. By addressing these considerations, it will be possible to optimize the utilization of plastic waste in road construction and contribute to a greener and more sustainable future.

Experimental Study on Cementless PET Mortar with Marble Powder and Iron Slag as an Aggregate

There has been an increase in plastic production during the past decades, yet the recycling of plastic remains relatively low. Incorporating plastic in concrete can mitigate environmental pollution. The use of waste polyethylene terephthalate (PET) bottles as an aggregate weakens properties of concrete. An alternative is to use PET bottles as a binder in the mortar. The PET binder mixed with sand results in weak mortar. Marble and iron slag can enhance PET mortar properties by preventing alkali reactions. This study examines the mechanical and durability properties of PET mortar with different mixes. The mixes were prepared as plastic and marble (PM); plastic and iron slag (PI); plastic, sand, and marble (PSM); plastic, iron slag, and marble (PIM); and plastic, sand, and iron slag (PSI). PM with 30-45% plastic content had increased compressive and flexural strength up to 35.73% and 20.21%, respectively. PI with 30-35% plastic content showed strength improvements up to 29.19% and 5.02%, respectively. However, at 45% plastic content, strength decreased by 8.8% and 27.90%. PSM, PIM, and PSI specimens had nearly double the strength of ordinary Portland cement (OPC) mortar. The durability of PET mortar in chemical solutions, mainly 5% HCl and 20% NaOH, indicate that mass decreased after 3, 7, and 28 days. All specimens showed good resistance to HCl and NaCl solutions compared to OPC mortar. However, its resistance to NaOH is low compared to OPC mortar. PET mortar without cement showed higher strength and durability than cement mortar, making it suitable for paver tiles, drainage systems, and roads.

Feasibility Study of Using Hydrophobic Geopolymer-Based as Aggregate Substitution in Asphalt Mixture

Hydrophobic aggregates have the great ability to prevent asphalt pavement roads from stripping-off of the asphalt in presence of water. In addition, they give the option to consume less asphalt and save cost. On the other hand, natural aggregates have been found to be non-renewable and rare. Geopolymer based artificial aggregates are great materials as they demonstrated to have exceptional features, such as high strength, superior durability, and greater resistance to fire exposure. In this study, a new hydrophobic geopolymer based aggregate has been produced with rice ash (RA) and fly ash as precursors as well as, Sodium Hydroxide (NaOH) and Sodium Silicate (Na₂SiO₃) as activators. The mechanical properties combined with the softening coefficient, surface properties of samples, contact angle and adhesion were characterized as well as microstructure X-ray diffraction (XRD) and Scanning electron microscopy (SEM) test. The results indicate that the activators Na₂SiO₃/NaOH at a mix ratio of 1 have a suitable effect on the pores and the compressive strength of the new artificial aggregate most particularly sodium hydroxide. Nonetheless, it has been found that coating the artificial aggregate with asphalt showed a great improvement of the hydrophobic nature of the produced artificial aggregate based geopolymer. Hence, indicates the possibility of using it as recycle aggregate pavement. From a microstructure point, the hydrophobic nature of the new alkali-activated artificial aggregate can be improved by increasing the quantity of mullite in the mix proportion design.

Prediction of Strength Properties of Concrete Containing Waste Marble Aggregate and Stone Dust-Modeling and Optimization Using RSM

Carbon footprint reduction, recompense depletion of natural resources, as well as waste recycling are nowadays focused research directions to achieve sustainability without compromising the concrete strength parameters. Therefore, the purpose of the present study is to utilize different dosages of marble waste aggregates (MWA) and stone dust (SD) as a replacement for coarse and fine aggregate, respectively. The MWA with 10 to 30% coarse aggregate replacement and SD with 40 to 50% fine aggregate replacement were used to evaluate the physical properties (workability and absorption), durability (acid attack resistance), and strength properties (compressive, flexural, and tensile strength) of concrete. Moreover, statistical modeling was also performed using response surface methodology (RSM) to design the experiment, optimize the MWA and SD dosages, and finally validate the experimental results. Increasing MWA substitutions resulted in higher workability, lower absorption, and lower resistance to acid attack as compared with controlled concrete. However, reduced compressive strength, flexural strength, and tensile strength at 7-day and 28-day cured specimens were observed as compared to the controlled specimen. On the other hand, increasing SD content causes a reduction in workability, higher absorption, and lower resistance to acid attack compared with controlled concrete. Similarly, 7-day and 28-day compressive strength, flexural strength, and tensile strength of SD-substituted concrete showed improvement up to 50% replacement and a slight reduction at 60% replacement. However, the strength of SD substituted concrete is higher than controlled concrete. Quadratic models were suggested based on a higher coefficient of determination (R²) for all responses. Quadratic RSM models yielded R² equaling 0.90 and 0.94 for compressive strength at 7 days and 28 days, respectively. Similarly, 0.94 and 0.96 for 7-day and 28-day flexural strength and 0.89 for tensile strength. The optimization performed through RSM indicates that 15% MWA and 50% SD yielded higher strength compared to all other mixtures. The predicted optimized data was validated experimentally with an error of less than 5%.

A Comparative Review of Hot and Warm Mix Asphalt Technologies from Environmental and Economic Perspectives: Towards a Sustainable Asphalt Pavement

The environmental concerns of global warming and energy consumption are among the most severe issues and challenges facing human beings worldwide. Due to the relatively higher predicted temperatures (150-180 °C), the latest research on pavement energy consumption and carbon dioxide (CO₂) emission assessment mentioned contributing to higher environmental burdens such as air pollution and global warming. However, warm-mix asphalt (WMA) was introduced by pavement researchers and the road construction industry instead of hot-mix asphalt (HMA) to reduce these environmental problems. This study aims to provide a comparative overview of WMA and HMA from environmental and economic perspectives in order to highlight the challenges, motivations, and research gaps in using WMA technology compared to HMA. It was discovered that the lower production temperature of WMA could significantly reduce the emissions of gases and fumes and thus reduce global warming. The lower production temperature also provides a healthy work environment and reduces exposure to fumes. Replacing HMA with WMA can reduce production costs because of the 20-75% lower energy consumption in WMA production. It was also released that the reduction in energy consumption is dependent on the fuel type, energy source, material heat capacity, moisture content, and production temperature. Other benefits of using WMA are enhanced asphalt mixture workability and compaction because the additives in WMA reduce asphalt binder viscosity. It also allows for the incorporation of more waste materials, such as reclaimed asphalt pavement (RAP). However, future studies are recommended on the possibility of using renewable, environmentally friendly, and cost-effective materials such as biomaterials as an alternative to conventional WMA-additives for more sustainable and green asphalt pavements.

Concrete Performance Attenuation of Mix Nano-SiO2 and Nano-CaCO3 under High Temperature: A Comprehensive Review

Fire and extreme heat environmental changes can have an impact on concrete performance, and as climate change increases, new concrete structures are being developed. Nano-silica and nano-calcium carbonate have shown excellent performances in modifying concrete due to their large specific surface areas. This review describes the changes in concrete modified with nano-silica (NS) and nano-calcium carbonate (NC), which accelerate the hydration reaction with the cementitious materials to produce more C-S-H, resulting in a denser microstructure and improved mechanical properties and durability of the concrete. The mechanical property decay and visualization of deformation of mixed NS and NC concrete were tested by exposure to high temperatures to investigate the practical application of mixed composite nanomaterials (NC+NS) to concrete. The nano-modified concrete had better overall properties and was heated at 200 °C, 400 °C, 600 °C and 800 °C to relatively improve the mechanical properties of the nano concrete structures. The review concluded that high temperatures of 800 °C to 1000 °C severely damaged the structure of the concrete, reducing the mechanical properties by around 60%, and the dense nano concrete structures were more susceptible to cracking and damage. The high temperature resistance of NS and NC-modified nano concrete was relatively higher than that of normal concrete, with NC concrete being more resistant to damage at high temperatures than the NS samples.

A systematic review of the utilization of waste materials as aggregate replacement in stone matrix asphalt mixes

The daily utilization of a large amount of raw materials is causing a rapid depletion of natural resources. The growth of the human population is accompanied by higher activities in the agricultural and manufacturing sectors that resulted in a larger volume of waste materials being disposed of in landfills each year. Researchers are seeking ways to reduce the adverse impact of waste materials on the environment. One method for managing waste materials is using them as a substitute for natural materials, for example, as aggregate replacement in the construction of road pavements. This paper reviews the previous studies that explored the use of waste materials as aggregate replacement in stone matrix asphalt (SMA) mix and the performance of asphalt pavements constructed using these materials. A systematic literature search of four databases revealed that waste materials could be used as an alternative to the natural aggregates. Future studies on the SMA mixes should investigate using other waste materials that could improve mix design and enhance pavement performance. There is a need to establish a standard code of practice and train material technologists to use different types of waste in SMA pavement construction. In summary, it is essential to perform a life cycle cost analysis (LCCA) and life cycle assessment (LCA) to quantify the economic and environmental impacts of the different waste materials used as aggregates in SMA.

Pavement maintenance management framework for flexible roads: a case study of Pakistan

Roads play a pivotal role in the overall economic growth of any country. Developed countries allocated sufficient budget to make new roads and to maintain the existing roads. They also have a proper pavement management system (PMS) in practice to manage roads, whereas developing countries suffer from budgetary issues to make new roads and maintain the existing road network. Therefore, this paper explores the awareness of PMS via direct and indirect methods in Pakistan with a proposed framework of the low-cost model and pavement maintenance indicators for developing countries. This paper also performs a scientometric assessment of PMS. A detailed literature review has been carried out for this study, followed by a quantitative study from experienced professionals. The scientometric data is collected from the Scopus database from 1975 to 2020, whereas the data for PMS awareness assessment has been collected using questionnaires from different experts working directly and indirectly in the road management sector. The data has been analyzed using the arithmetic mean because of the nature of the questions and scope of the study. The direct method results show that experts are aware of PMS for a new road, but they have no PMS to rehabilitate roads. The indirect method results show that the authorities are applying various components of PMS, but there is no proper PMS in practice. This paper helps decision-makers to make better decisions and policies for improved road maintenance and rehabilitation. The proposed framework in the study can significantly assist the UN-SDG 9 (Facilitate Sustainable Infrastructure in Developing Countries) and 11 (Affordable and Sustainable Transport System).