بتن های سبز و بتن های سنتی
Abstract
Graphical abstract
۱٫ Introduction
۲٫ Literature review
۳٫ Methods
۴٫ Results and discussion
۵٫ Conclusion
CRediT authorship contribution statement
Declaration of competing interest
Acknowledgements
References
Abstract
The sustainable development of green concrete consumes as few natural resources as possible during production and uses and utilizes recyclable waste materials as raw materials. This study summarizes three modes of green concrete production: recycled aggregate concrete production mode, fly ash concrete production mode, and circular economy concrete production mode, as well as the system emergy flow of each mode of production, and presents emergy analysis methods for each mode. With the help of emergy ternary diagram auxiliary lines, the emergy ternary diagram expressions of three green concrete production modes and traditional concrete production modes are analyzed, respectively. The ternary diagram of emergy analysis directly reflects the resource allocation of the system. The relationship between the emergy utilization ratio and the indicators of the system is analyzed, and the sustainability of the existing concrete production system is evaluated comprehensively. The R-resource line corresponds to the environmental load ratio. The closer the R-resource line is to the F-axis, the greater the environmental pressure of the system. The N-resource line corresponds to emergy yield ratio and emergy investment ratio. The closer the N-resource line is to the N-axis, the greater the energy input-output efficiency of the system. The closer the N-resource line is to the “۰” point of the R-axis, the higher the utilization rate of outsourced resources. In the emergy ternary diagram, it is evident that the circular economy concrete production mode is more sustainable than the other three concrete production modes. Combined with the analysis of the sensitivity line and sustainability line, it is predicted that the concrete production mode along the direction of the R-Sensitivity line is a sustainable development path.
Introduction
China’s concrete production ranks first in the world; its annual concrete production is 53% greater than the total of all other countries worldwide. Further, China’s cement production is the highest worldwide as well. Its output in 2012 was 2.15 billion metric tons, 8.6 times that of India, the second highest producer, and 29 times that of the United States, the third highest producer (Oh et al. 2014). In China, concrete products and components, concrete mixing stations, and other construction methods are adopted, and about two billion cubic meters of concrete are used in national projects and infrastructure construction annually. According to statistics regarding the production and operation of the national key ready-mixed concrete enterprises (groups), put out by the China Concrete and Cement Products Association, the actual output of ready-mixed concrete enterprises (groups) in China totaled 2.103 billion cubic meters in 2017. Thus, related quality and environmental protection problems about concrete production can not be ignored.