Are totally recycled hot mix asphalts a sustainable alternative for road paving
TL;DR: In this paper, the authors evaluated the effectiveness of rejuvenator agents in improving the aged binders' properties and the recycled mixture performance and concluded that totally recycled asphalt pavement can be a good alternative for road paving, especially if rejuvenators are used to reduce their production temperature and improve their performance.
Abstract: The recycling of reclaimed asphalt pavement (RAP) helps road authorities to achieve their goal of a sustainable road transport system by reducing waste production and resources consumption. The environmental and economic benefits of using RAP in hot mix asphalt (HMA) applications could be pushed up to the limit, by producing totally recycled HMAs (100% RAP), but the performance of this alternative must be satisfactory. In fact, these mixtures could possibly present problems of workability and durability, higher binder aging and low fatigue cracking resistance. Thus, the objective of this study is to determine if totally recycled HMA mixtures could be a good solution for road paving, by evaluating the merit of some rejuvenator agents (commercial product; used engine oil) in improving the aged binders’ properties and the recycled mixture performance. Several binder samples were prepared with the mentioned rejuvenators and characterized (Pen, R&B and dynamic viscosity), in order to select the best rejuvenator contents. The production temperatures of the corresponding recycled mixtures were evaluated based on their workability. Totally recycled HMAs were produced with the best previously observed combinations, and their performance (water sensitivity, rutting resistance, stiffness, fatigue resistance, binder aging) was assessed. The main conclusion of this study is that totally recycled HMAs can be a good alternative for road paving, especially if rejuvenator agents are used to reduce their production temperature and to improve their performance.
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TL;DR: In this paper, the state-of-the-art approaches for increasing the amount of reclaimed asphalt pavement (RAP) in asphalt mixtures above 40% are summarized and methods to optimise the mix design as well as production technology in order to allow manufacturing of such sustainable mixtures are described.
Abstract: Asphalt is the most recycled material in the USA at a re-use rate of 99%. However, by average only 10–20% reclaimed asphalt pavement (RAP) is used in a given mix design and large part of the RAP is degraded for use in lower value applications. The amount of RAP in asphalt mixtures can be significantly increased with the application of good RAP management practice, readily available modern production technologies and advanced knowledge of mix design. This paper summarises the state-of-the-art approaches for increasing the amount of RAP in asphalt mixtures above 40%. The production challenges and common pavement distresses of very high RAP content mixtures are identified and methods to optimise the mix design as well as production technology in order to allow manufacturing of such sustainable mixtures are described. The best practices for RAP management and economic benefits of high RAP use are also discussed.
249 citations
TL;DR: A holistic evaluation of the feasibility of producing 100% recycled asphalt pavement mixtures is presented in this article, where a cradle-to-gate analysis of environmental effects indicated 18 kg or 35% CO2eq savings per t of produced 100% RAP asphalt mixture compared to virgin mix, while cost analysis showed at least 50% savings in material related expenses.
Abstract: a b s t r a c t A holistic evaluation of the feasibility of producing 100% recycled mixtures is presented. Eleven tech- nologies readily available for producing 100% Reclaimed Asphalt Pavement (RAP) hot asphalt mixtures are described in the article and the complementary video (http://youtu.be/coj-e5mhHEQ). The recorded performance of 100% RAP mixtures is analyzed along with identification of typical high RAP distresses. Recommended mix design procedures and the best RAP management strategies are described. A cradle- to-gate analysis of environmental effects indicated 18 kg or 35% CO2eq savings per t of produced 100% RAP asphalt mixture compared to virgin mix, while cost analysis showed at least 50% savings in material related expenses.
241 citations
TL;DR: In this paper, the effect of waste edible vegetable oil on the rejuvenation of aged asphalt binders was investigated in terms of physical, chemical and rheological properties, and it was shown that waste vegetable oil can effectively soften aged asphalt.
231 citations
01 Jan 2014
TL;DR: A holistic evaluation of the feasibility of producing 100% recycled asphalt pavement (RAP) mixtures is presented in this paper, where a cradle-to-gate analysis of environmental effects indicated 18 kg or 35% CO2eq savings per t of produced 100% RAP asphalt mixture compared to virgin mix, while cost analysis showed at least 50% savings in material related expenses.
Abstract: a b s t r a c t A holistic evaluation of the feasibility of producing 100% recycled mixtures is presented Eleven tech- nologies readily available for producing 100% Reclaimed Asphalt Pavement (RAP) hot asphalt mixtures are described in the article and the complementary video (http://youtube/coj-e5mhHEQ) The recorded performance of 100% RAP mixtures is analyzed along with identification of typical high RAP distresses Recommended mix design procedures and the best RAP management strategies are described A cradle- to-gate analysis of environmental effects indicated 18 kg or 35% CO2eq savings per t of produced 100% RAP asphalt mixture compared to virgin mix, while cost analysis showed at least 50% savings in material related expenses
216 citations
TL;DR: In this article, a hybrid LCA was used to analyze the environmental footprint of using a reclaimed asphalt pavement (RAP) content in asphalt binder mixtures, and the results showed significant reductions in energy consumption and greenhouse gas (GHG) emissions with an increase in RAP content.
Abstract: With the pavement industry adopting sustainable practices to align itself with the global notion of habitable environments, there has been growing use of life-cycle assessment (LCA). A hybrid LCA was used to analyze the environmental footprint of using a reclaimed asphalt pavement (RAP) content in asphalt binder mixtures. The analysis took into consideration the material, construction, and maintenance and rehabilitation phases of the pavement life cycle. The results showed significant reductions in energy consumption and greenhouse gas (GHG) emissions with an increase in RAP content. The contribution of the construction phase to the GHGs and energy consumption throughout pavement life cycle is minimal. Feedstock energy, though not consequential when comparing asphalt mixtures only, has a significant impact on total energy. Based on LCA analysis performed for various performance scenarios, breakeven performance levels were identified for mixtures with RAP. The study highlighted the importance of achieving equivalent field performance for mixtures with RAP and virgin mixtures.
179 citations
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TL;DR: In this article, the blending process of reclaimed asphalt pavement (RAP) with virgin mixture was analyzed through controlled experiments, where one type of screened RAP was blended with virgin (new) coarse aggregate at different percentages.
Abstract: This paper presents a laboratory study in which the blending process of reclaimed asphalt pavement (RAP) with virgin mixture was analyzed through controlled experiments. One type of screened RAP was blended with virgin (new) coarse aggregate at different percentages. A blended mixture containing 20% of screened RAP was subjected to staged extraction and recovery. The result from this experiment indicated that only a small portion of aged asphalt in RAP actually participated in the remixing process; other portions formed a stiff coating around RAP aggregates, and RAP functionally acted as "composite black rock." The resulting composite layered structure was desirable to improve the performance of the hot-mix asphalt mixture.
294 citations
01 Mar 2007
TL;DR: In this article, an in-depth review of the literature related to RAP was conducted to determine the appropriate level of contribution that should be given to the residual asphalt binder in RAP, and the level of interaction between aged and virgin binders was then used to investigate the influence on the performance and the durability of the mixtures as compared to virgin HMA.
Abstract: While the state of Illinois has been recycling Reclaimed Asphalt Pavement (RAP) material into hot-mix asphalt (HMA) since 1980, there continues to be questions regarding the correct approach to design HMA with RAP. The Illinois Department of Transportation's current method of RAP HMA design provides 100% contribution for the residual asphalt binder from the RAP based on solvent extractions. This means that the amount of virgin asphalt binder is reduced by the full amount of asphalt binder in the RAP for the percentage specified. This has recently been reported to be inaccurate and could result in an erroneous HMA job mix formula and may cause dry HMA. Hence, the HMA may become vulnerable to durability cracking and premature failure. The objective of this research project is to develop an understanding of the interaction between aged and virgin asphalt binders in RAP. Based on this understanding, this study will determine the appropriate level of contribution that should be given to the residual asphalt binder in RAP. The level of interaction between aged and virgin binders will then be used to investigate the influence on the performance and the durability of the mixtures as compared to virgin HMA. As a first step in this research project, an in-depth review of the literature related to RAP was conducted. This report presents the findings of the literature review and its implication on this research project. Availability of this report will also serve future research projects dealing with RAP materials.
220 citations
TL;DR: In this article, three recycled materials (recycled hot mix asphalt, asphalt rubber, and glassphalt) and the traditional hot-mixed asphalt are compared, assuming that the thickness of the asphalt is 5 cm and the service life is 6 years.
Abstract: This research performed life cycle inventory using proposed recycled material formulas and service records and incorporating the database provided by Eco-indicator 99 in order to study the eco-burden presented by using recycled materials to rehabilitate asphalt pavements. Three recycled materials (recycled hot mix asphalt, asphalt rubber, and Glassphalt) and the traditional hot-mixed asphalt are compared. Assuming that the thickness of the asphalt is 5 cm and the service life is 6 years, the eco-burden presented by the traditional hot-mixed asphalt is 3.45 kPt. per lane-kilometer. Using recycled hot mixed asphalt can reduce the eco-burden by 23% under the same conditions. Using asphalt rubber increases the eco-burden by 16%, while the eco-burden remains essentially the same (reduced by less than 1%) using Glassphalt. Taking into account the difference in service life between different materials, this research also uses a 40-year time span to evaluate the eco-burden for each material. The results show that the traditional hot mixed asphalt has an eco-burden of 23.03 kPt. for that time span. Both recycled hot mixed asphalt and asphalt rubber can reduce the eco-burden by 23% in the same period. On the contrary, Glassphalt increases the eco-burden by 19%. This research also identified the sources of the eco-burden for these asphalts. The results show that a large percentage of the eco-burden comes from two sources, the asphalt binder used (39–48%) and the heat sources required to process these paving materials (42–50%). This suggests that the most effective way to lower the eco-burden may be to reduce the heat requirement during the manufacturing process.
182 citations
TL;DR: In this article, the effect of RAP variability on bituminous mixtures was analyzed by determining the stiffness modulus and indirect tensile strength and cracking and fatigue behaviour of two semi-dense mixtures of 12 and 20mm maximum aggregate size.
181 citations
TL;DR: In this article, a specific laboratory study aiming at perfectioning recycled asphalt with high mechanical performance, for surface and structural layers of flexible pavements, was conducted, where the aim was to combine in the same material the maximum possible quantity of recycled asphalt (RA), coming from degraded asphalt layers, together with high structural performance of the recycled mixtures obtained (mainly stability, load spreading properties, rutting and fatigue resistance) that should not be lower, or possibly better than those offered by traditional asphalt mixture, made with virgin binder and aggregate.
Abstract: The paper deals with a specific laboratory study aiming at perfectioning recycled asphalt with high mechanical performance, for surface and structural layers of flexible pavements. The aim of the research was to combine in the same material the maximum possible quantity of recycled asphalt (RA), coming from degraded asphalt layers, together with high structural performance of the recycled mixtures obtained (mainly stability, load spreading properties, rutting and fatigue resistance) that should not be lower, or possibly better than those offered by traditional asphalt mixture, made with virgin binder and aggregate. For this purpose, innovative recycled mixtures, close-graded and with high mechanical performance, characterized by high content of recycled asphalt (up to 50%) and designed for surface, binder and base layers were investigated in a laboratory study. The results of physical and mechanical characterization tests show that, by controlling the homogeneity of recycled material and by using new bitumen with adequate rheological properties, it is possible to obtain paving mixtures with high content of recycled materials that, in relation to their intended use (surface, binder or base layer), can be considered as “high-performance mixtures”.
101 citations