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The purpose of this paper is to study the unit train make-up scheme for loaded direction in the heavy haul railway.

A 0-1 nonlinear integer programming model with the aim of minimizing the idling period between actual train arrival time and expected train arrival time for all loaded unit trains are proposed.

The proposed model is applied into a case study based on Daqin heavy haul railway. Results show that the proposed model can offer operators an optimal unit train make-up scheme for loaded direction in heavy haul railway.

The proposed model can offer operators an optimal unit train make-up scheme for loaded direction in heavy haul railway.

This study aimed to identify barriers impeding circular economy (CE) uptake in the construction industry in literature, categorize them for the development of a framework and to seek the interrelationships among the categorized barriers. This allowed for identifying integrated solutions to holistically address the barriers. The study also sought to identify the “hot” themes, the knowledge gaps and future research directions on barriers impeding CE.

Forty-eight relevant articles were desk reviewed from different construction peer-reviewed journals and published conference papers. A scientometric analysis allowed for co-occurrence of keywords relating to CE. A content analysis enabled the identification of 79 barriers impeding the uptake of CE in the construction industry which were further categorized into six distinct categories for the development of a framework showing the interrelationships among the categorized barriers.

The identified barriers include construction sector inertia, lack of design standards, lack of knowledge, awareness and understanding, design cost, and perception of second-hand materials as substandard among others. The study categorized the identified barriers for better understanding into six different groups: cultural barriers, social barriers, environmental barriers, economic barriers, technical barriers and technological barriers. Strategies to address the barriers were also proposed. The interrelationships among the various barriers were also shown in a proposed framework to educate professionals on the interconnectivity of the barriers.

Categorization of the various barriers impeding CE uptake contributes to the body of knowledge. Also, the interrelationships among the various categorized barriers in the framework will enable construction professionals make informed decisions regarding the successful integration of CE in the industry, better appreciate the barriers that impede CE uptake and apply strategies to holistically address the barriers. This will expand current knowledge outside the narrow scope of isolated barriers.

To the global construction industry, the review presents a list of barriers and their interrelationships that could provide implementation strategies for the uptake of CE in the industry.

The geographical scope of this study is not limited, and therefore encourages wide applicability of the findings to the global construction industry.