Abstract
Steady increase in overexploitation of stone quarries, generation of construction and demolition waste, and costs of preparing extra landfill space have become environmental and waste management challenges in metropolises. In this paper, aggregate production is studied in two scenarios: scenario 1 representing the production of natural aggregates (NA) and scenario 2 representing the production of recycled aggregates (RA). This study consists of two parts. In the first part, the objective is the environmental assessment (energy consumption and CO2 emission) and economic (cost) evaluation of these two scenarios, which is pursued by life-cycle assessment (LCA) method. In the second part, the results of the first part are used to estimate the optimal combination of production of NA and RA and thereby find an optimal solution (scenario) for a more eco-friendly aggregate production. The defined formulas and relationship are used to develop a model. The results of model validation show that the optimal ratio, in optimal scenario, is 50%. The results show that, compared to scenario 1, optimal scenario improves the energy consumption, CO2 emissions, and production cost by, respectively, 30%, 36%, and 31%, which demonstrate the effectiveness of this optimization.
Highlights
It has been reported that a developed country like Australia produces 8.7 million tons of waste demolition concrete, 1.3 million tons of waste brick, 3.3 million tons of waste excavation rock, 1 million tons of waste glass, and 1.2 million tons of waste asphalt every year [1]
The model was coded based on the defined formulas and relationships, and specifications of the case study were imported into the developed program
Given the results obtained for the combination of production of natural aggregates (NA) and recycled aggregates (RA), the optimal ratio was found to be 50%
Summary
It has been reported that a developed country like Australia produces 8.7 million tons of waste demolition concrete, 1.3 million tons of waste brick, 3.3 million tons of waste excavation rock, 1 million tons of waste glass, and 1.2 million tons of waste asphalt every year [1]. According to other statistics [2], 42% of all wastes in Australia are related to construction and demolition (C&D) waste, and of this amount 81% is waste concrete. 29% of solid waste produced in the United States is C&D waste [2], and the amount of waste concrete discarded in this country is about 30 million tons per year [3]. Japan is far more environmentally friendly in this respect, as only 16% (750 thousand tons) of its waste generation is related to C&D (efficient reuse of materials prevents disposal in landfills) [2]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
