“Encouraging Sustainable Use of RAP Materials for Pavement Construction in Oman: A Review” by principal investigator Husam al Dughaishi, Lecturer at the College of Engineering and Architecture at the University of Nizwa, is one of the innovative research projects of the past couple of years that aims to improve sustainable infrastructure in the Sultanate of Oman. Researcher Husam al Dughaishi stated that the Sultanate of Oman has experienced rapid development over the last thirty years and has constructed environmentally friendly and sustainable infrastructure while it continues to find economical alternative resources to achieve the goals of Oman Vision 2040. However, he mentioned that the primary concerns are preserving natural resources and reducing the impact of carbon dioxide (CO₂) emissions on the environment. Through this research project, Al Dughaishi aimed to encourage the sustainable use of reclaimed asphalt pavement (RAP) materials in pavement construction and focus primarily on employing RAP materials in new pavement projects. He explained that currently, new construction projects utilise a significant percentage of demolished asphalt pavement to save costs and natural resources. However, the key issue that arises when mixing RAP into new asphalt mixtures is the effects on the mixtures’ resistance to permanent disfigurements, such as fatigue cracks, that influence asphalt mixture performance. Husam further added that numerous studies have assessed the impact of using RAP in asphalt mixtures and found that RAP increases the stiffness of asphalt mixtures, and thus improves rutting resistance at high temperatures.
Nevertheless, the findings for thermal and fatigue cracking were found to be contradictory. This study therefore addressed the primary concerns regarding the use of RAP in asphalt pavements and aimed to encourage highway agencies and academic researchers in the Gulf countries to develop frameworks for the practical usage of RAP in the construction of sustainable pavement systems. The main findings of this research project revealed that the design and manufacture of a high-quality RAP mixture is more challenging than conventional asphalt and thus should be done by experienced pavement engineers, and that the RAP mixture design is dependent on the standards, scope of application and the impact of RAP technologies on the environment and economy. Moreover, Al Dughaishi maintained that assembling homogeneousness in RAP material quality checks is essential and should be carried out from the commencement phase of old pavement reclamation to its final paving. He added that the CIR method is often used for rehabilitation and construction work because it consumes less energy, emits fewer greenhouse gases, and is more cost-effective than other on-site pavement recycling methods. The RAP application encouragements as a value are used as a granular base material for roadways, airport runways, shoulders, engineered fill, and culvert backfill. This research project was published under MDPI's Recycling journal, which is a well-regarded, open-access journal in the field of sustainable recycling, waste management, and material recovery. The research team consisted of Husam al Dughaishi, Abdulrahman Milad, Jawad al Lawati, Munder Bilema, Ali Mohammed Babalghaith, Nuha S Mashaan, and Nur Izzi. The research project was supported by the Publication Support Programme of the Ministry of Higher Education, Research and Innovation (MoHERI), which is a programme concerned with supporting the publication of research papers in the best-classified journals, most prestigious peer-reviewed periodicals, and highest-rated specialised databases.
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