الفهرس 
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Abstract
Since the early nineties, there has been an increasing interest in enhancing environmental awareness and introducing sustainability concepts, as well as green technologies into the pavement industry. In addition, economic and population growth along with the expansion of urban areas stipulate the construction of larger road networks, which leads to the depletion of natural resources. Hence, two approaches were the focus of researchers to develop the sustainable pavement industry, warm mix asphalt (WMA) technology, and reuse (recycling) of waste/byproduct materials in pavement construction such as construction and demolition (C&D) waste or recycled concrete aggregate (RCA) and nano-silica fume (NSF). The main objective of this study is to evaluate the possibility of using recycled concrete aggregate (RCA) as an alternative to coarse natural aggregates (NAs) in Warm Mix Asphalt (WMA). The investigated asphalt mixtures were WMA with two types of additives (Sasobit and Asphamin) and one Hot Mix Asphalt (HMA) as a control mix. The index engineering characteristics of the RCA used for the asphalt mixtures were determined. The physical and rheological characteristics of virgin and modified asphalt binders were specified using penetration, softening point, Brookfield rotational viscometer (RV), and Dynamic Shear Rheometer Tests (DSR) tests. Moreover, MATLAB image processing was utilized to verify the quality of asphalt coating versus mixing temperature on prepared loose mixtures at the optimal Sasobit content to determine the suitable mixing temperature range and compare it with the obtained results from RV. The WMA was manufactured by two approaches. The first approach involved modifying the asphalt binder properties by incorporating Sasobit as an organic additive into the heated asphalt binder (Wet process). The second approach incorporated Asphamin as a synthetic zeolite foaming additive into the aggregate during the mixing process (Dry process). Then, the nano-silica fume (NSF) was used as an economical nanomaterial to improve the investigated WMA’s performance compared to a control HMA. The performance of the asphalt mixes in terms of Marshall, indirect tensile strength (ITS), dynamic modulus (E*), and flow number (FN) was also estimated. Moreover, a comparative life cycle assessment (LCA) analysis was performed using OpenLCA 1.10.3 software and the TRACI v.2.1 impact assessment method for modelling and characterizing the environmental performance of the asphalt mixtures investigated in this study. For the performance tests, the Marshall test results of WMA mixtures with the two types of additives were relatively identical to the control HMA mixture with a slight difference in the optimum asphalt content (OAC). However, the NSF incorporation as a replacement to the mineral filler within the WMA mixtures led to an increase in stability values by up to 35%, especially at 40% NSF with low OAC. The tensile strength ratio (TSR) values for WMA mixes were lower than 80%, but the use of NSF showed a slight enhancement in their values to meet the minimum requirement set by Egyptian specifications. Also, the results revealed a decrease in E* and FN values for the WMA mixtures than those for the HMA control, while the addition of NSF enhanced the results significantly to outperform the HMA. As for the life cycle assessment analysis, the results showed that the impact of the processes associated with the production of RCA is the best for all the analyzed impact categories than NA. In addition, the environmental impact results of the WMA mixture with Sasobit as an organic additive were lower than those of HMA by 5-10%, while WMA with aspha-min as a synthetic zeolite additive increased the environmental impact values by 4-43%. In terms of production cost, the HMA showed the lowest cost compared to WMA. Also, the use of RCA as a substitution to NA yielded a slight decrease of up to 4% in the total production of the asphalt mixtures.