Recycled Pavement Research Articles

Molecular model and its evolution during secondary regeneration of asphalt based on molecular dynamics

With the use of recycled asphalt pavement, numerous recycled pavements will suffer from damages which needs to be regenerated for the second time (i.e. secondary regeneration). The mechanism and impact of secondary regeneration may diverge from those observed during primary regeneration. To study the aging and regeneration mechanism of secondary regenerated asphalt, the molecule models of regenerant and asphalts under different aging states were established through the molecular dynamics (MD). The double-layer diffusion models were constructed to examine the fusion behavior of new and aged asphalts. Based on this, the dynamic viscosity, rotational viscosity, bulk modulus, and shear modulus of secondary regenerated asphalt were predicted. The findings indicate that the established molecular models have a strong correlation with real asphalt molecules. During secondary regeneration, the deepening of asphalt aging reduces the fusion velocity and efficiency between aged and new asphalts. The introduction of regenerant can enhance the diffusion velocity between the aged and new asphalts, yet it does not necessarily improve their fusion degree. During the process of secondary regeneration, the shear modulus of secondary aged asphalt can be effectively restored by adding regenerant, but the recovery of dynamic viscosity, rotational viscosity and bulk modulus presents poor trends when compared to the primary regeneration.

The use of asphalt waste dust for stabilization of sustainable pavement recycling

The asphalt waste dust as a sustainable material for stabilizing pavement recycling, which is cold in-place recycling (consists of reclaimed asphalt pavement, crushed rock aggregate base, and ordinary Portland cement), was presented in this study. To understand the effect of asphalt waste dust on stabilizing pavement recycling, 10–30 wt% asphalt waste dust was added and compared with the behavior of pure old-asphalt pavement material and old-asphalt pavement material mixed with 3.5 % OPC. The compaction test, unconfined compressive strength test (UCS), indirect tensile strength tests (IDT), and scanning electron microscope analysis were conducted under various mixing conditions. The addition of asphalt waste dust up to 20 wt% achieved desirable results of UCS and IDT involved with microstructural development, which were beyond the standard requirements of the base course from the Department of Rural Roads and the Department of Highway. A maximum of 20 wt% asphalt waste dust can be utilized for practical use with pavement recycling in the base course.

Study on the Road Performance and Compaction Characteristics of Fiber-Reinforced High-RAP Plant-Mixed Hot Recycled Asphalt Mixtures.

Recycled asphalt pavement (RAP) mixtures are widely adopted due to their significant economic and social benefits from utilizing pavement recycling materials. This study incorporates basalt fibers (BF) and polyester fibers (PF) into plant-mixed hot recycled asphalt mixtures to analyze their enhancement effects on the high-temperature, low-temperature, and fatigue performance at different RAP content levels. Additionally, the study investigates the impact of fiber and RAP additions on the compaction characteristics of the mixtures using gyratory compaction tests, aiming to increase the RAP content of plant-mixed hot recycled asphalt mixtures. Experimental results demonstrate that at 30% and 50% RAP content levels, basalt fibers exhibit more pronounced enhancement effects on the performance of recycled asphalt mixtures compared to polyester fibers. Incorporating basalt fibers increases the fracture energy of recycled asphalt mixtures by 8.63% and 13.9%, and improves fatigue life by 154% and 135%, respectively. Moreover, the addition of both types of fibers increases compaction difficulty, with polyester fibers showing a more significant influence on the compaction energy index (CEI).

Experimental study on creep-fatigue damage of hot central plant recycling asphalt mixture containing high RAP

The objective of this study is to delve into the nonlinear damage evolution mechanism of hot central plant recycling asphalt mixture under the influence of creep-fatigue interaction. A predictive model for lifespan, considering the interaction of temperature and load, was developed. Dynamic creep tests were conducted at different temperatures to assess the creep effect of the asphalt mixture under actual road temperature conditions. The investigation began by acknowledging the material's viscoelastic properties, thereby deriving the loss compliance value - a key indicator of temperature effects - using an equivalent conversion factor and a viscoelastic mechanics model. This allowed for the incorporation of creep behavior into the load system. Furthermore, to analyze the nonlinear damage mechanism and fatigue prediction mechanism, direct tensile fatigue tests were performed at different temperatures and different stress levels. The fatigue damage evolution law of hot central plant recycling asphalt mixture containing high RAP considering the creep effect was revealed, and the fatigue life evaluation method under the combined action of temperature and stress level was proposed. The results show that the fitting degree of the time-temperature conversion equation and the viscoelastic mechanics model to the test data is more than 0.9, and the derived loss compliance value better captures the creep effect. Based on the nonlinear creep-fatigue damage model, the damage law of high-RAP hot central plant recycling asphalt mixture was identified. The optimized fatigue life prediction model fully considers the combined effect of temperature and stress level and analyzes the influence parameters of the real state of pavement fatigue. The prediction accuracy is within the requirements of engineering applications. The model's predictive accuracy meets the criteria for engineering applications, enhancing the multifaceted damage coupling analysis approach for hot central plant recycling asphalt mixture and predict the service life of recycled pavements under complex conditions, establishing a groundwork for the prediction and assessment of long-lasting recycled pavements.

Evaluating the Performance of Concrete Containing Reclaimed Asphalt Pavement as Coarse Aggregate

Reclaimed asphalt pavement is a recycled pavement material consisting of asphalt and aggregate that has been treated. The majority of RAP is recycled back into pavements; hence there is a general dearth of data on the properties of RAP in other prospective uses such as Portland cement concrete. In this work, the characteristics of Portland cement concrete with coarse RAP were examined in the laboratory. Further, basalt fibers have been employed in the concrete mix to enhance the properties of concrete. The different proportions of RAP have been added into the concrete as a replacement to coarse aggregate for finding the optimum dosage for enhancing strength and durability. All samples were tested for workability, compressive strength, flexural strength, and acid attack tests to investigate the impact of RAP as coarse aggregate on concrete performance. The test results indicate that the inclusion of RAP makes concrete more workable while decreasing its strength. The reason for this is the inadequate adhesion between the cement matrix and RAP aggregate. Additionally, the durability and strength of RAP concrete are improved by the incorporation of basalt fibers. In addition to RAP as a partial substitute for coarse aggregate, the investigation suggests employing basalt fibers. Index Terms: Reclaimed asphalt pavement, workability, Strength, Durability, Replacement, Fly ash, Sustainability.

Unlocking the potential of epoxy binders for efficient reclaimed asphalt pavement recycling: an experimental and molecular simulation study

ABSTRACT The efficient utilisation of reclaimed asphalt pavement (RAP) has emerged as a critical focal point within pavement recycling technology. High-performance epoxy binders show promise in achieving this objective. This study investigates the interaction mechanisms between epoxy systems and aged asphalt from three perspectives: macroscopic properties, microscopic phase structures, and molecular structure of the asphalt-epoxy system. Results reveal that the aged asphalt-epoxy system has increased elongation at break and decreased tensile strength. Microscopic assessments show that the phase structure of the aged asphalt-epoxy system is denser compared to neat asphalt-epoxy systems. The looser structure of neat asphalt-epoxy systems provides more space for epoxy system chemical reactions, leading to higher crosslinking compared to both pure epoxy and aged asphalt-epoxy systems. Additionally, the epoxy system exhibits better compatibility with aged asphalt than neat asphalt. At the molecular level, the epoxy system strongly adsorbs onto asphalt components, especially aged resin molecules. These findings contribute to the scientific application of epoxy binder in pavement recycling technology.

Investigation into the effect of waste engine oil and vegetable oil recycling agents on the performance of laboratory-aged bitumen

The pavement recycling method is one of the practical ways to integrate sustainable development into transportation infrastructure, and it has been adopted worldwide. The use of reclaimed asphalt pavement (RAP) in new asphalt highways is limited due to the ageing effects caused by UV damage and weathering on the asphalt binder. To address this issue, waste vegetable oil (WVO) and waste engine oil (WEO) have been proposed as potential rejuvenating agents to enhance the recyclability of pavements containing RAP. This study evaluated the effectiveness of WEO and WVO as chemical rejuvenating agents through various tests on both aged and virgin asphalt binders. The tests included measurements of ductility, fire, and flash points, softening points, and penetration. The results indicate that the addition of WEO and WVO can improve the low-temperature properties of asphalt binders when mixed with RAP, resulting in reduced stiffness. The mixture containing WEO and WVO exhibited improved stability compared to the control, suggesting enhanced flow with increasing waste oil content in comparison to aged binder, albeit with slightly reduced flow compared to the virgin binder. This study demonstrates the potential of WEO and WVO as recycling agents to enhance the performance of bituminous mixes incorporating RAP.

Multiscale optimization on polymer-based rejuvenators for the efficient recycling of aged high-viscosity modified asphalt: Molecular dynamics simulation and experimental analysis

With the depletion of fossil fuels, the advancement of efficient pavement recycling technology has garnered widespread attention, which contributes to the promotion of sustainable economic and environmental development. The polymers in polymer-based composite rejuvenators (PBCRs) are the key to restoring the performance of aged high-viscosity modified asphalt (HVMA). To optimize the polymers in PBCRs, this study investigates the rejuvenation effect and interface diffusion mechanism of various PBCRs using molecular dynamics simulation and experimental analysis. First, four PBCRs with different polymer components were designed, and their impact on the performance of weather-aged HVMA were examined using the rheological test, low-temperature force ductility test, crack resistance test, and aging resistance test. Subsequently, the rejuvenation effects of four PBCRs were ranked using the comprehensive performance radar chart. Finally, molecular models and layer models of weather-aged HVMA and four PBCRs were constructed, and the diffusion fusion process and interaction mechanism were analyzed using the molecular dynamics simulation. The findings indicate that PBCRs can rebuild the polymer network structure, partially restore the rheology, elastic recovery, and low-temperature ductility of aged HVMA. Additionally, PBCRs significantly reduce the crack potential of aged HVMA and ensure satisfactory aging resistance. Molecular dynamics simulation shows that due to the differences in their molecular structures, the diffusion ability of PBCRs is ranked as follows: crumb rubber rejuvenator (CR + R) > SBR rejuvenator (SBR + R) > SBS rejuvenator (SBS + R) > HVM rejuvenator (HVM + R). In summary, SBS + R proves most effective in regulating asphalt components and rebuilding the polymer network structure, but its interfacial diffusion ability is inferior to CR + R and SBR + R. CR + R has the highest diffusion coefficient, but its rejuvenation effect is not ideal. HVM + R is slightly less effective at rejuvenation than SBS + R, but has the worst diffusion capacity. The rejuvenation effect and diffusion ability of SBR + R are both not ideal. This study has significant implications for optimizing the polymers in PBCRs and promoting the efficient rejuvenation and eco-friendly sustainable development of HVMA.

Comprehensive evaluation of energy consumption and carbon emissions of asphalt pavement recycling technology

To assess the energy saving and emission reduction effects of recycling technology, the quantitative analysis of energy consumption and carbon emission of recycled asphalt pavement is conducted of asphalt mixture production, transportation, paving and compaction. Firstly, the calculation model for energy consumption and carbon emissions of recycled asphalt pavement is established during the construction stage. In addition, the energy consumption and carbon emission of four recycling technologies, including the HCPR, HIR, CCPR and CIR, were compared. Finally, the FCE method is used to evaluate the actual effect of energy saving and emission reduction from the perspectives of the ecological benefit and the economic benefit. The research results indicate the most serious stage of energy consumption is the new material production stage, and the most serious stage of carbon emission is the asphalt mixture production stage of recycled asphalt pavement. Taking the HCPR technology as an example are calculated in detail. The energy consumption of the HCPR technology in the four stages of the construction stage was 17.59 MJ, 344.45 MJ, 228.51 MJ and 25.85 MJ, respectively, and the emissions in the four stages of the construction stage were 1307.89 g, 5971.28 g, 19,251.24 g and 1949.82 g, respectively. For different recycling technologies in the construction stage, the energy-saving ratios of HCPR, HIR and CCPR are 13.62%, 9.61% and 19.24% respectively when compared with the typical scheme, which have a certain energy-saving effect. However, the energy consumption of CIR reduced by 43.63%, which the energy saving effect is most significant. Moreover, the emission reduction ratios of HCPR, HIR and CCPR are 2.3%, 9.23% and 1.01% respectively when compared with the typical scheme, the emission of CIR reduced by 30.76%, so the emission reduction effect of CIR is most significant. Furthermore, the comprehensive evaluation score of the CIR technology with the most significant energy saving and emission reduction effect is 0.8021 in terms of ' ecological benefits ' and 0.8074 in terms of ' economic benefits '. In summary, it is recommended to adopt CIR technology in the engineering project, which can achieve the most significant energy-saving and emission reduction effects.

Influence of rejuvenator components on rheological properties of recycled bitumen in the full temperature range

Recovering aged bitumen from reclaimed asphalt pavement (RAP) is crucial for the evolution of pavement recycling. This study delves deeply into the effects of rejuvenator components on the rheological properties of rejuvenated bitumen across a wide temperature range. The investigation utilized the rolling thin film oven test (RTFOT) and the pressure aging vessel (PAV) test to simulate the short-term and long-term aging of the bitumen binder, respectively. Four distinct rejuvenators were then applied to recover the bitumen at varied aging levels. Detailed chemical analyses, encompassing the four-fraction (SARA) method and Fourier transform infrared spectroscopy (FTIR), were employed to identify the chemical compositions and key functional groups of both the rejuvenators and the rejuvenated bitumen. The rheological behavior of rejuvenated bitumen was assessed through a comprehensive series of tests, including conventional, temperature sweep, frequency sweep, multiple stress creep recovery (MSCR), linear amplitude sweep (LAS), and bending beam rheometer (BBR) tests. A Pearson correlation analysis highlighted a significant positive association between specific rejuvenator components, notably asphaltene (As), saturate (S), and aromatic (Ar), and the high-temperature performance of the rejuvenated bitumen. The findings of this research offer insights into the formulation of rejuvenators, potentially enhancing the performance of rejuvenated asphalt pavements and facilitating sustainable infrastructure advancements.

The effect of RAP content on fatigue damage property of hot reclaimed asphalt mixtures.

The fatigue property of the recycled mixture affects the structural design of recycled pavement. In order to explore the effect of different reclaimed asphalt pavement (RAP) content on the fatigue properties of recycled mixtures, the fatigue properties of recycled mixtures were analyzed through an indoor fatigue test and finite element numerical simulation. Based on the phenomenological method and the dissipated energy theory, the fatigue properties of recycled mixtures with different RAP contents were analyzed and the fatigue damage of the mixtures were also studies under various strain levels. Based on the finite element numerical model of fatigue damage, the stress distribution and internal damage field distribution of trabecular specimens under different temperatures, strain levels and RAP contents were analyzed. The results showed that the anti-fatigue level of the mixture decreased as the RAP content was increased. The relative change rate of dissipated energy for different types of mixtures showed a two-stage change rule with the change of load times, that is, the value is large and decreasing, and the value is small and stable. The correlation between the plateau value (PV) and the fatigue life was established under the double logarithm coordinates, which could better analyze the influence law of the RAP content on the fatigue performance of the recycled mixture. Under different temperatures, strain levels, and RAP contents, the stress at the bottom of trabecular specimen and the overall damage field were mainly generated at the upper part under compressive stress and the bottom under tensile stress, and the damage field distribution area accounted for a small part of the whole specimen. According to the test results and fatigue damage distribution, it is recommended that the content of recycled aggregate in recycled asphalt mixtures be less than 30% to ensure good performance. The research results have important practical significance for the improvement of fatigue performance and engineering application of recycled mixtures.

Study on the Performance of High Content RAP Recycled Mixture

The performance of RAP material directly affects the engineering effect of pavement recycling technology. In this study, the performance of high content RAP recycled mixture was analyzed. Through the extraction and screening of RAP materials, it was found that the viscosity of old asphalt increased significantly, the softening point decreased, and the coarse aggregate was refined seriously. The high, low temperature and water stability of high content plant mixed recycled ATB-25 mixture were studied through laboratory tests with different regenerants. The results showed that, compared with the control group, the dynamic stability, freeze-thaw splitting strength ratio and the maximum flexural tensile strain increase rate were: Type A regenerant: 27.48%, 29.45%, 35.71%; Type B regenerant: 16.76%, 21.28%, 38.96%. Comparing the effects of the two kinds of regenerants, after adding Type A regenerant, the mixture has the best high-temperature and water stability, and Type B regenerant is better than Type A regenerant in improving the low-temperature performance. The high, low temperature and water stability of the mixture after adding the regenerant can meet the specification requirements.

Evaluating the Influence of Waste Cooking Oil Molecular Structure on Aged Asphalt Modification

Recycling aged asphalt pavement has become increasingly important due to its environmental and economic advantages. Asphalt, serving as the binding agent for aggregates, plays a crucial role in pavement integrity. The deterioration of asphalt binder properties upon aging poses a significant challenge to asphalt pavement recycling. Consequently, various rejuvenators have been developed to restore aged asphalt binder properties and facilitate pavement reclamation. Waste cooking oil (WCO) is a widely used rejuvenator that mitigates the high viscosity and brittleness of aged asphalt, preventing cracking. WCO consists of triglycerides (TG) and free fatty acids (FFA), each with distinct molecular structures. In this study, molecular dynamics simulations were employed to investigate the individual effects of 10 wt.% TG and FFA on the viscosity, self-diffusion, and microstructure of aged asphalt at 1 atm and 404 K. The results demonstrate that both TG and FFA can reduce the viscosity of aged asphalt, albeit through different mechanisms. TG and FFA, characterized by high molecular mobility when dispersed in aged asphalt, enhance its mobility and reduce its viscosity. Additionally, TG effectively disrupts preferential interactions among asphaltenes, preventing their self-aggregation. In contrast, FFA has a limited impact on reducing these interactions. Furthermore, the study delves into the entanglement behaviors of FFA and TG with varying chain lengths within aged asphalt. Shorter chain lengths, as opposed to longer ones, exhibit a lower likelihood of entanglement with other asphalt molecules, resulting in increased molecular mobility and reduced asphalt viscosity. The fundamental insights gained from this research serve as a valuable reference for the application of waste cooking oil in the recycling of aged asphalt pavement. By shedding light on underlying molecular dynamics, this study contributes to the development of more effective and sustainable approaches to asphalt recycling.

The Significance of the Factors Increasing the Asphalt Pavement Recycling Rate in the Country, Determined Using Multiple-Criteria Decision-Making Methods

Asphalt pavement, a component of transport infrastructure, deteriorates under the influence of destructive factors. The damages which have occurred during its period of use are repaired and the asphalt pavement is recycled when its further rehabilitation is economically and technically irrational. The material from the asphalt pavement layer that has reached its limit state is milled out or broken and crushed and then is repeatedly used in the production of hot-mix asphalt (HMA) or warm-mix asphalt (WMA) mixtures. In this paper, the dynamics of the percentage recycling ratio (RR) of old asphalt pavement material was investigated. RR represents the quantity of reclaimed asphalt pavement (RAP) used in the production of HMA and WMA mixtures in Europe and the USA, divided by the total amount of RAP prepared in the country. Factors and goals affecting it are analyzed. An original system of 10 criteria that increase the RR country has been created. Decision makers do not know which factors have the maximum influence in increasing the use of RAP and this should go in connection with environmental pollution reduction and achieving economic utility. By applying different multiple-criteria decision-making (MCDM) methods and using the importance given to these criteria by 14 experts, the normalized subjective weights of the criteria were determined. Analytic hierarchy process (AHP), rank correlation, average rank transformation into weight—linear (ARTIW-L) and non-linear (ARTIW-N), and direct percentage weight (DPW) methods were used in the study. The results show that the RAP recycle rate is close to 100% in countries with a sustainable economic background. In the Baltic countries, it is mostly increased by the adequacy of regulatory documents, the strategy promoting asphalt recycling in the country, and the homogeneity and classifying of RAP. The number and capacity of RAP stocks, the number and productivity of asphalt milling equipment and the wear and tear of the asphalt pavement have the least influence on the increase in RR. The opinions of experts in assessing the significance of all criteria are consistent. The averages of the weights of criteria determined by four MCDM methods (AHP, ARTIW-L, ARTIW-N, DPW) made it possible to obtain more reliable results. These results can be used to make strategic decisions and to create a plan of practical actions to increase the RAP recycling rate in the developing countries.

Characterization of Recycled Aggregates in Existing Pavement Base Layers

ABSTRACT The use of recycled pavement materials in transportation infrastructure projects has contributed positively to maintaining a sustainable flow of construction materials and sources. Geotechnical properties of recycled pavement materials play a major role in the suitability of such materials for use in civil infrastructure. This study aimed at evaluating the properties of recycled concrete aggregates (RCA) and reclaimed asphalt pavements (RAP) used as base layer materials in existing hot mix asphalt pavements (with service life of more than 8 years) and comparing them with virgin crushed aggregate (CA) base materials of similar service life. Coring of flexible pavement surface layers at 18 pavement sites was performed to expose the base course layer materials for sampling and testing. Then, the dynamic cone penetrometer (DCP) test was conducted in which the cone penetrated through base layers to the subgrade when possible. Thereafter, base materials were retrieved from the pavement sites for laboratory testing and evaluation. Laboratory tests consisted of particle size analysis, specific gravity and absorption, and Micro-Deval abrasion. Analysis of the particle size distribution showed the presence of high sand size fractions in both RCA and RAP base materials compared with virgin CA base materials. This indicated the recycled materials were crushed/milled to smaller size fractions or degraded under freeze-thaw cycles and traffic loads during the pavement’s service life, or both. The RCA base materials exhibited the highest absorption and mass loss in the Micro-Deval test. The DCP test results were used to predict California bearing ratio (CBR) and resilient modulus (Mr) of base materials. The predicted CBR and resilient modulus of the recycled base materials showed that RCA, RAP, and CA all had comparable strength and modulus values that were high. The investigated recycled RCA and RAP aggregates possessed properties that are comparable with the properties of the virgin CA.

Effects of multiple recycling on the performance characteristics of asphalt binder using different recycling agents

The process of reclaimed asphalt pavement (RAP) recycling may occur multiple times during the life of the pavement. This study investigates the effect of multiple recycling on binder properties by employing a virgin 3045 PEN grade binder that was aged in the laboratory intended to simulate aging of binders in RAP. The aged binder was rejuvenated using two bio-oils and one softer binder. The doses of the bio-oils and softer binder were determined by matching the continuous high-temperature performance grade (PGH) of the rejuvenated RAP binder to that of the virgin binder. This aging and rejuvenation cycle was repeated three times. Finally, fatigue and rutting performance of the binder was evaluated for the three reuse levels. Results indicate that the material can be reused up to three cycles keeping good performance on fatigue or rutting. However, care should be taken regarding the cumulative effect of bio-oils causing an over-softening effect on the of the RAP.

Unraveling the nano-cracking mechanism in aged asphalt binder with consideration of rejuvenation effects

For achieving the sustainable utilization of reclaimed asphalt pavement, a popular approach is to incorporate rejuvenators to restore the cracking resistance of aged asphalt. However, research on the nanoscale rejuvenation mechanisms and the relationship with the cracking behavior is limited. To address this challenge, this study utilizes molecular dynamics simulations to explore the fundamental cracking mechanism in aged asphalt and elucidate how rejuvenators affect this process. A multiphysics analysis, including mechanical response, morphology relationship, energy evolution, deagglomeration and lubrication behavior is developed to comprehend the nano-cracking mechanism. Computational findings reveal that the cracking failure originates form cavitation, and the process primarily includes nanovoid formation, enlargement, filamentation, and separation. Oxidation enhances the aggregation of asphaltene molecules and reduces intermolecular rearrangement and mobility, which fundamentally accelerates the nano-cracking process. Owing to the diffusion of rejuvenators and their disturbances to asphaltene π-π stacking, rejuvenators can penetrate into aged asphalt molecules, lubricate and reduce intermolecular friction. This facilitates molecular rearrangement during the cracking process, thereby improving the cracking resistance and energy performance of aged asphalt binder. The finding from this study contributes to elucidating the fundamental cracking mechanism in rejuvenated asphalt binder and promoting the sustainable utilization of recycled pavement materials.

Laboratory Fatigue Characterization of Foamed Bitumen Stabilized Granular Base and Recycled Blends for Pavements

ABSTRACT Foamed bitumen stabilization offers a sustainable solution for the construction of new pavements or rehabilitation treatments while also improving the performance of pavement structures. This technique allows up to 100 % of the existing pavements to be used, which will lead to lower use of quarry resources and reduced material transportation cost. In recent years, there have been advances in the use of foamed bitumen stabilized (FBS) pavements. However, prior to the research in this paper, no specific Australian performance relationship had been developed for FBS materials. Also, there was a lack of test procedures specifically developed to manufacture and evaluate the fatigue cracking resistance of FBS conventional and recycled pavement materials. This paper presents the laboratory characterization and development of a fatigue relationship to predict performance of FBS materials. For this purpose, laboratory experiments were undertaken including flexural fatigue, modulus, and strength tests using a four-point bending beam system. Five different host materials were selected for laboratory investigations, including three crushed rocks and two recycled blends incorporating 50 % reclaimed asphalt pavement and 80 % recycled cement–treated crushed rock. A total of eight FBS mixes were tested with varying host materials, foamed bitumen content from 2 to 4 %, and hydrated lime content of 1 or 2 %. A testing procedure to measure and analyze the fatigue performance of FBS granular base and recycled blends was produced. Using the laboratory test results, a specific laboratory fatigue relationship for FBS materials, including recycled blends, is developed. The flexural modulus, flexural strength-to-modulus ratio, and volume of bitumen were found to be major parameters affecting the fatigue life of FBS materials and were consequently employed to develop the predictive model. This research will assist with the subsequent development of a performance-based in-service fatigue model for thickness design of FBS flexible pavements.

Study on the release characteristics of volatile organic compounds from different aged asphalt

The recycling of old asphalt pavements has enormous economic and environmental value. Current studies on the recycling of old asphalt mainly focus on the changes in engineering properties. However, volatile organic compounds (VOCs) during recycling are less considered, potentially impacting ecology and human health. This study investigated the effect of aging methods on the release characteristics of asphalt VOCs. The correlation between the physical and chemical properties of asphalt and the release characteristics of VOCs was revealed. Firstly, the influence of different aging methods on the physicochemical properties of asphalt was also analyzed. Then, the VOC release characteristics of different aged asphalts were analyzed by gas chromatography-mass spectrometry. Finally, Pearson correlation analysis was conducted to investigate the relationship between the physicochemical properties of asphalt and the release characteristics of VOCs. The results showed that the release characteristics of VOC fractions changed significantly after asphalt aging. VOCs of aged asphalt exhibited a lower proportion of alkanes, alkene, aromatic hydrocarbons, and halogenated hydrocarbons and a higher proportion of oxygenated compounds. The release characteristics of aged asphalt VOCs are more significantly influenced by temperature than those of virgin asphalt. The results of Pearson analysis indicated a significant correlation between the release characteristics of asphalt VOCs and their physicochemical properties.

Experimental Examination on Use of Recycled Materials in Stone Matrix Asphalt

SMA (stone matrix asphalt or stone mastic asphalt) was initially discovered in German & European and countries as impermeable or highly resilient wearing surface for bridge decks. Generally, it consists of two parts, a binder rich mortar and a coarse aggregate. It is made by a mixture of crushed fine and coarse aggregates, stabilizer such as polymers or fibres, cement & mineral filler. In present work, an effort has been made to study the properties of Stone Matrix Asphalt mixes with cellulose fibre and using recycled pavement material as well as slag in partial replacement of stone aggregates as coarse and fine aggregate grades. This research project was done to check the usage of recycled pavement material in Stone Matrix Asphalt mixture by conducting Marshall test in the lab in which flow & stability value was examined along with other properties of mixtures. Here IRC -SP-79 specification, aggregate gradation is taken for stone matrix asphalt. Binder used is 60/70 penetration grade bitumen. Binder content is varied as 4%, 5%, 5.5%, 6%, and 7% by weight of aggregates and fibre used is optimum fibre content at 0.3% by the weight of aggregate. Key Words: SMA (Stone Matrix Asphalt), RAP (Recycled Asphalt Pavement)