Performance Evaluation of Recycled-Concrete Aggregates and Reclaimed-Asphalt Pavements for Foam-Mix Asphalt Mixes
01 Oct 2020-Journal of Materials in Civil Engineering (American Society of Civil Engineers)-Vol. 32, Iss: 10, pp 04020295
TL;DR: In this paper, mechanical foaming of bitumen is a popular technique employed to reduce the viscosity of binder for ensuring coating of aggregates at lower temperature, and the potential of this technique is b...
Abstract: Mechanical foaming of bitumen is a popular technique employed to reduce the viscosity of binder for ensuring coating of aggregates at lower temperature. The potential of this technique is b...
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TL;DR: In this paper , the authors developed a trade-off methodology based on the Life Cycle Assessment (LCA) technique and statistical analysis to determine the maximum RCA content to be incorporated into WMA without generating greater environmental impacts.
46 citations
TL;DR: In this article , a methodology was developed to optimize the design of Warm Mix Asphalt (WMA) with the inclusion of three recycled materials as partial replacement of natural aggregates (NAs), namely Crumb Rubber (CR), Reclaimed Asphalt Pavement (RAP), and Recycled Concrete Aggregate (RCA).
Abstract: In this research, a methodology was developed to optimize the design of Warm Mix Asphalt (WMA) with the inclusion of three recycled materials as partial replacement of natural aggregates (NAs), namely Crumb Rubber (CR), Reclaimed Asphalt Pavement (RAP), and Recycled Concrete Aggregate (RCA). The methodological proposal is composed of 4 sections denominated: (I) environmental module, (II) economic module, (III) decision-support module, and (IV) results report module. Initially, a Life Cycle Assessment (LCA) is carried out to quantify the environmental impacts associated with WMA production. Similarly, in the second module, a Life Cycle Costing (LCC) is performed to estimate the financial investment required by the process under evaluation. Meanwhile, a computational model based on genetic algorithms (GAs) is created in the decision-support module to execute multi-objective optimization (minimization of costs and contaminating potential). In the last module, the more accurate WMA designs are presented employing a Pareto front, ternary plot, composition pie chart, and statistical analysis of the influence of the CR, RAP, and RCA on the validation criteria. This study concludes that even under long hauling distances and huge prices, it is possible to design WMA with CR, RAP, and/or RCA additions that form sustainability benefits compared to conventional WMA.
35 citations
TL;DR: A review of the utilization of reclaimed asphalt pavement aggregates in roller compacted concrete pavement (RCCP) mixes is presented in this paper, where several issues and factors affecting the fresh and hardened properties of RCCP mixes due to the incorporation of RAP are discussed.
28 citations
TL;DR: In this paper , the characteristics and performance of these materials when used as aggregates in asphalt mixtures are reviewed and discussed, and it is possible to conclude that incorporating SSA or RCA in asphalt mixture for road pavements has functional, mechanical, and environmental advantages.
Abstract: Various researchers are developing efforts to integrate waste and by-products as alternative materials in road construction and maintenance, reducing environmental impacts and promoting a circular economy. Among the alternative materials that several authors have studied regarding their use as partial or total substitutes for natural aggregates in the asphalt paving industry, the steel slag aggregate (SSA) and recycled concrete aggregate (RCA) from construction demolition waste (CDW) stand out. This paper reviews and discusses the characteristics and performance of these materials when used as aggregates in asphalt mixtures. Based on the various studies analyzed, it was possible to conclude that incorporating SSA or RCA in asphalt mixtures for road pavements has functional, mechanical, and environmental advantages. However, it is essential to consider some possible drawbacks of these aggregates that are discussed in this paper, to define the acceptable uses of SSA and RCA as sustainable feedstocks for road paving works.
14 citations
TL;DR: In this article , the authors proposed three methods to determine the optimal design conditions (coarse RCA content) that minimize the environmental burdens caused by WMA-RCA production.
Abstract: Warm Mix Asphalts (WMAs) are asphalt concretes produced at lower temperatures than traditional Hot Mix Asphalts (HMAs). Nonetheless, the above is not enough to diminish the environmental impacts associated with the road infrastructure industry. Accordingly, incorporating Recycled Concrete Aggregate (RCA) as a partial replacement for Natural Aggregates (NAs) in WMA design has been gaining notoriety in the literature as a viable alternative to increase sustainability. However, the eco-friendly manufacturing of WMA with RCA contents (WMA-RCA) is not easy to obtain satisfactorily because the RCA causes alterations in the mix design. Thus, this research proposes three (3) methods to determine the optimal design conditions (coarse RCA content) that minimize the environmental burdens caused by WMA-RCA production. The first method is a mathematical model based on Multiple Linear Regression (MLR), which is used as a benchmark for the other two methods. The second and third methods are computational models based on Artificial Intelligence (AI), i.e., Artificial Neural Networks (ANNs) and Genetic Algorithms (GAs), respectively. Notably, the Life Cycle Assessment (LCA) was employed as the theoretical framework to support all the proposed models. Consequently, this study concludes that: (i) all the proposed methodological alternatives achieve results with a great accuracy; (ii) the GAs model is the most precise method in terms of error minimization; (iii) the MLR model is the fastest method in terms of execution time; and (iv) the ANNs model is the method that requires the longest time of running, and its exactness is at a midpoint concerning the other models.
13 citations
References
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TL;DR: In this article, the authors investigated the use of recycled concrete aggregates (RCA) as sustainable aggregates in Hot Mix Asphalt (HMA) for low-volume roads.
215 citations
TL;DR: In this paper, a comprehensive laboratory evaluation of physical and shear strength characteristics of recycled C&D materials was undertaken using gradation, Los Angeles Abrasion, unconfined compression, California Bearing Ratio (CBR), direct shear and consolidated drained triaxial tests.
212 citations
TL;DR: In this paper, the improvement of the properties of asphalt concrete shows the positive effect of polypropylene fibers, and the fiber-reinforced asphalt mixture exhibits good resistance to rutting, prolonged fatigue life and less reflection cracking.
204 citations
TL;DR: In this article, the reinforcement mechanism of bitumen mixed with fibers was investigated and it was shown that the reinforcement effect increases with increasing fibers up to a critical fraction, where fibers start to interact with each other, resulting in lower toughness.
Abstract: This paper investigates the reinforcement mechanism of bitumen mixed with fibers. Fibers including cellulose, rock wool and polyester types were added to bitumen. The viscosity, toughness and tenacity, microscopy and rheological tests were conducted to characterize the engineering properties of bitumen-fiber mastics. Test results indicate that the reinforcing effect increases with increasing fibers up to a critical fraction. With higher mixing temperatures, there is a higher viscosity ratio of mastic to bitumen. The tensile strength of bitumen-fiber mastics also increases with increasing fiber concentrations because the fibers carry parts of tensile loads. With the increasing tensile strength, it is implied that there is a good adhesion between bitumen and fibers. Scanning electron micrographs show that fibers reinforce bitumen through a three dimensional structure. However, there is a critical fiber fraction when fibers start to interact with each other, resulting in lower toughness. The optimum fiber content is dependent on fiber type, length and diameter.
153 citations
TL;DR: In this article, the effects of polyester fiber on the rheological characteristics and fatigue properties of asphalt and its mixture are investigated, and the results show that the viscosity of asphalt binder is increased with increasing polyester fibers, especially at lower temperature.
150 citations