Properties Of Asphalt Mixtures Research Articles

Evaluating the fracture characterization of asphalt mixtures under freeze-thaw damage based on full-field measurements

Understanding the fracture characterization of asphalt mixtures is important to improve pavement performance in seasonal frozen regions. It is necessary to analyze the cracking characteristics and mechanism of asphalt mixtures under the action of freeze–thaw damage. The semi-circular bending (SCB) crack test combined with digital image correlation (DIC) was conducted to evaluate the fracture characterization of asphalt mixtures under freeze–thaw cycles. The X-ray scanning measurement, bending beam rheology (BBR) test, oblique shear test, the generalized Maxwell model (GM), and the cohesive zone model (CZM) were utilized to reconstruct the 3D heterogeneous finite element (FE) model and reveal the damage mechanism. The results indicated that the freeze–thaw cycles negatively affected the cracking resistance of asphalt mixtures. After 20 freeze–thaw cycles, the fracture energy, stiffness, flexibility index, stress intensity factor, and crack evolution rate decreased by 22.96%, 19.53%, 63.93%, 63.93%, and 61.15%, respectively. The FE model was able to reflect the mechanical properties of asphalt mixtures with different numbers of freeze–thaw cycles well. The FE model can well reflect the mechanical properties of asphalt mixtures under different numbers of freeze–thaw cycles. It also reveals the deterioration of asphalt mortar properties and interfacial adhesion under the action of freeze–thaw damage, which leads to the reduction of internal stress transfer efficiency and attenuation of cracking resistance of asphalt mixtures. This study contributed to the damage mechanism evaluation of asphalt mixtures in seasonal frozen regions and may help with pavement design, construction, and maintenance.

Influence of Bamboo Fiber Content on the Properties of Asphalt Mixtures

Inspecting what how much bamboo fiber means for the attributes of asphalt mixtures and searching for ways of further developing maintainability and execution. To assess the impacts of bamboo fibers on significant qualities including soundness, rutting opposition, weakness conduct, and dampness helplessness, asphalt details coordinate these sustainable and ecologically harmless fibers. This review evaluated the presentation improving use of bamboo fiber, a new expansion to the regular fiber family, in stone matrix asphalt (SMA) and dense-grade (DG) mixes. As well as having a harsh surface like that of a typical lignin fiber, bamboo fiber has a high rigidity in the fiber course. Furthermore, bamboo fiber has satisfactory warm dependability, an issue with plant-based materials that is normally raised. The ideal asphalt cover contents for DG and SMA mixtures with differing measures of bamboo fiber were picked utilizing the Marshall blend plan procedure. Utilizing the wheel following test, inundation Marshall test, freeze-defrost cycle test, and three-point twisting bar test, separately, the impacts of bamboo fiber on blend dampness helplessness, rutting, and low-temperature breaking execution were surveyed. The presentation of the previously mentioned blend was fundamentally worked on by the expansion of bamboo fiber, as indicated by test results. All in all, blends including bamboo fiber exhibited execution that was either tantamount to or better than those containing polyester and lignin fiber, proposing that bamboo fiber can be utilized in asphalt mixtures.

Effect of asphalt modified with waste engine oil on the durability properties of hot asphalt mixtures with reclaimed asphalt pavement

Abstract The increased demand for asphalt and other materials involved in the construction of pavement led to an increase in the cost of these materials, which calls for searching for alternatives to virgin materials that can be used to produce asphalt mixtures. Reclaimed asphalt pavement (RAP) was employed in this study and regenerated using oxidized asphalt modified with waste engine oil (WEO). This method can achieve economic and environmental benefits. After improving the properties of oxidized asphalt using WEO, it was used with reclaimed asphalt mixtures (RAP). When the RAP was added at ratios of 20, 30, 40, and 50%, an improvement can be noticed in the mechanical performance of the asphalt mixtures renewed with oxidized asphalt and WEO and an increase in its resistance to stripping. When reclaimed asphalt pavement (RAP) is added to hot mix asphalt (HMA) at concentrations of 20, 30, 40, and 50%, respectively, the Marshall stability of HMA is improved by 10, 20, 28, and 9.5%, the flow is declined by 1% for all ratios of RAP except for 50% RAP where the flow decline by 3%, the unit weight is enhanced, the quantity of air voids in the mix is preserved within allowable ranges, and the resistance to stripping is increased by 62, 77, 85, and 76%, respectively. Research also shows that incorporating 40% RAP enhances the resistance to moisture by about 5.9%. The addition of 40% RAP reduced the Cantabro loss values by about 2 and 16% for both aging and non-aging samples, respectively. The rutting resistance increased by 50 and 47% for mixes with 40% RAP at 50 and 60°C, respectively. As a result, it became evident that mixtures containing RAP material could be effectively adapted to satisfy the relevant volumetric and performance requirements.

Experimental Study on Dynamic Modulus of High Content Rubber Asphalt Mixture

Currently, the research on the mechanical properties of rubber-modified asphalt mixtures primarily focuses on small-scale investigations, with insufficient exploration into the performance of rubber particles and their relationship with the mechanism and properties of modified asphalt mixtures. Limited studies have been conducted on large-scale rubber modification in asphalt mixtures. Due to frequent use and subsequent high damage to existing asphalt pavements, incorporating rubber-modified asphalt mixtures can partially alleviate premature deterioration. Dynamic modulus tests were conducted using MTS equipment under unconfined conditions to investigate the viscoelastic behavior of rubber-modified asphalt mixtures with high rubber content and elucidate the influence of rubber particle content on the elastic deformation and recovery capability. The dynamic mechanical properties of the mixtures were determined at different loading rates, temperatures, and types of rubber-modified asphalt mixtures. Based on the test data, variations in the dynamic modulus, phase angle, storage modulus, loss modulus, loss factor, and rut factor of the rubber-modified asphalt mixtures under different loading frequencies, temperatures, and types were analyzed. The results demonstrate the pronounced viscoelastic behavior of rubber-modified asphalt mixtures. The mixtures exhibit enhanced elasticity at low temperatures and high frequencies, while their viscosity becomes more prominent at high temperatures and low frequencies. Under constant test temperatures, an increase in load loading frequency leads to a higher dynamic modulus; conversely, a decrease in dynamic modulus is observed with increasing test temperatures. The dynamic modulus of ARHM-25 at a frequency of 10 Hz is found to be 12.99 times higher at 15 °C compared to that at 60 °C, while at 30 °C, the dynamic modulus at 25 Hz is observed to be 2.72 times greater than that at 0.1 Hz. Furthermore, the rutting resistance factors of the asphalt mixtures increase with loading frequency but decrease with temperature. The rutting factor for ARHM-13 at a frequency of 10 Hz is found to be 22.98 times higher at 15 °C compared to that at 60 °C, while at a temperature of 30 °C, the rutting factor for this material is observed to be 3.09 times greater at a frequency of 25 Hz than at 0.1 Hz. These findings suggest that rutting is most likely when vehicles drive at low speeds in hot weather conditions.

Relationships between 3D linear viscoelastic properties of bitumen, asphalt mastics and asphalt mixtures using micromechanical models

In this paper, micromechanical models are used to predict the 3D viscoelastic behaviour of asphalt mixtures (with volume fraction of aggregate particles up to 87%) from the mechanical properties of their constituents. To fulfil the objective of study, complex modulus tests are conducted on bituminous materials at three different scales: bitumen, asphalt mastics and asphalt mixtures. The volume fraction of particles varies from 0% (bitumen) to 15%, 25%, 35% (asphalt mastic) and up to 87% (asphalt mixture). In the experimental program, complex modulus of bitumen, asphalt mastic and asphalt mixtures at different temperatures, frequencies are measured. For asphalt mixtures, measurements of complex Poisson’s ratio are also performed. The rheological model 2S2P1D is used to simulate the 3D viscoelastic behaviour of tested bituminous materials. From the experimental results and simulations, two micromechanical models (self-consistent and generalized self-consistent model) are used to predict the complex modulus and complex Poisson’s ratio of asphalt mixtures. The obtained results show that both micromechanical models give the good prediction of complex modulus for asphalt mastic where the volume fraction of aggregate particles is lower than 35%. At asphalt mixture scale where the volume fraction of particles is up to 87%, only simulation using the generalized self-consistent model can show good results. The prediction using the generalized self-consistent model at the mixture scale can be applied for both complex modulus and complex Poisson’s ratio. In addition, the prediction of complex modulus and complex Poisson’s ratio of asphalt mixtures becomes better when the asphalt mastic instead of bitumen is considered as viscous matrix.

Experimental study of improving hot mix asphalt reinforced with carbon fibers

Abstract Using hot asphalt mixtures (HMAs) is very common in flexible pavement construction due to its mechanical properties of durability, water resistance, and riding comfort. It proved to substantially reduce the applied stresses from vehicular traffic to subgrade. However, these types of pavements can undergo different types of distress such as cracks and rutting, which could be the result of weak mixing of the asphalt mixture and/or increasing traffic volumes. Therefore, the need to improve the mechanical properties of hot mix asphalt mixtures using different additives and modifiers was raised. Different materials have been recently used to reinforce asphalt concrete. For the construction of road pavements, using fibers in a HMA has emerged as a significantly more appealing option due to their strengthening properties. The alteration of asphalt binder is expected to benefit from carbon fibers (CFs) more than other types of fiber. In this study, an experimental study is carried out to investigate the effects of adding CFs to the asphalt mixtures with grades of (40–50) which comply with the Iraqi specifications. Twelve Marshall specimens were tested for stability and flow, 24 specimens for moisture failure testing, and two specimens for the rutting resistance of the asphalt mixture. The optimum bitumen content of 5.0% was used to prepare all the specimens. Different percentages of CFs by weight of asphalt (0, 0.2, 0.4, and 0.6%) were implemented to study the performance of paving mixtures. The way to mix the disperse the CFs homogeneously is by dry state (after separating the fibers manually) for 10 min, and then the asphalt was added; the mixture was heated to 165°C and mixed for at least 20 min. The results showed that the optimum properties of the HMA were reached by adding 0.4% CF to the HMA. Marshall stability was increased by 48%, the flow was decreased by 23%, and in addition, rut depth was reduced by 50%. The unit weight and the percentage of air voids in the mix were maintained and, along with other mix properties, are preserved within acceptable limits. Moreover, the indirect tensile strength has increased by 88.6%. Furthermore, moisture susceptibility reached 88%. Therefore, the addition of 0.4% CFs improved the performance of HMA at a high temperature of 60°C, which is close to the paving temperature in Iraq, by reducing the rutting of the asphalt mixture, which is considered the most dangerous tiling problem in Iraq. By improving the performance characteristics of asphalt mixture, the durability of the pavement will increase, and the riding will be more comfortable.

Study on the influence factors of fatigue properties of large-stone asphalt mixtures based on semi-circular bending tests

In order to alleviate the fatigue cracking problem of asphalt pavements. The development of large-stone asphalt mixtures (LSAM) is a worthwhile research direction. In this paper, different loading frequencies, test temperatures and stress ratios are designed to investigate the influence of semicircular bending (SCB) test conditions for LSAM fatigue properties. Comparative tests were also conducted with AC-13 fine-grained asphalt mixtures. The fatigue property of LSAM was analyzed by applying Paris' law, measuring fatigue crack length and using fatigue rupture energy theory. The test results indicated that fatigue life increased approximately 12 times with increasing loading frequency, 5 times with lower test temperatures, and 4 times with reduced stress ratio. Respectively, the magnitude of the single fatigue rupture energy and the total fatigue rupture energy also increased. Compared to AC-13 fine-grained asphalt mixtures, LSAM has a lower rate of rise in the displacement curve and smaller fracture displacement. After logarithmic transformation, the fatigue rupture energy and fatigue life of LSAM show an obvious linear relationship, specifically Wf=0.000806Nf1.12975. In summary, based on the SCB test conditions, LSAM exhibited superior fatigue performance compared to AC-13 fine-grained asphalt mixture. Additionally, LSAM demonstrated better resistance to fatigue loading-induced deformation.

Investigating the effects of ageing condition and type of aggregates on the properties of asphalt mixtures

In this study, asphalt mixtures made by steel slag (SSA), copper slag (CSA), limestone (LA) and siliceous (SA) aggregates were subjected to different aging conditions; and were evaluated using Marshall, indirect tensile strength (ITS), Cantabro abrasion loss and semi-circular bending (SCB) tests. Results reveal that the moisture damage, raveling and fracture resistance of asphalt mixture decrease with aging and the ITS and Marshall properties improve with aging. After 7-day long-term aging, the TSR of the mixtures made by LA, SA, SSA and CSA, decreases, 28.8%, 48.5%, 8.8% and 15%, respectively, while, the ITS in dry condition increases, 61.9%, 33%, 62% and 81%, respectively. The fracture properties and moisture damage resistance of asphalt concrete made by SSA and CSA are less affected by aging than those made by LA and SA. Statistical analysis revealed that the effect of aggregate type, aging condition and their interaction on the mixture properties is significant.

Assessing the Impact of Sustainable Recycled Concrete Aggregate on the Mechanical Properties of Hot Mix Asphalt Mixtures

Assessing the Impact of Sustainable Recycled Concrete Aggregate on the Mechanical Properties of Hot Mix Asphalt Mixtures

State of the Art Review of Ageing of Bituminous Binders and Asphalt Mixtures: Ageing Simulation Techniques, Ageing Inhibitors and the Relationship between Simulated Ageing and Field Ageing

Asphalt mixtures age during service in the field, primarily as the result of chemical changes in the bituminous binder phase. The ageing phenomenon changes the properties of the asphalt mixture, including the stiffness modulus, the resistance to deformation and the resistance to cracking, and it leads to surface weathering or erosion that often leads to pavement resurfacing. Consequently, many researchers have attempted to understand and to simulate the ageing of bituminous binders and asphalt mixtures in the laboratory. This review of bituminous binder and asphalt mixture ageing considers ageing simulation techniques, the effect of ageing on both bituminous binders and asphalt mixtures, the potential benefits of ageing inhibitors, and efforts to relate simulated laboratory ageing to observed field ageing. It is concluded that ageing has a significant effect on the properties of bituminous binders and asphalt mixtures, and that improved simulated ageing is important for comparing the effect of ageing on different materials and mixtures, as well as for quantifying the potential benefits of ageing inhibitors, which have generally been promising. It is also concluded that current ageing protocols are based on heat only, omitting the important contribution of solar radiation to the weathering and ageing of asphalt surfaces in the field. In the future, different simulated ageing protocols should be developed for binder and mixture samples. Similarly, a different ageing protocol is appropriate for understanding base-layer fatigue, compared to research on surface-layer weathering. Finally, it is concluded that a universal ageing protocol is unlikely to be found and that mixture- and climate-specific protocols need to be developed. However, given the importance of simulated ageing to asphalt researchers, the development of reliable, robust and calibrated laboratory ageing protocols is essential for the future.

RSM based modelling and optimization of Marshall properties of steel-slag and lime-modified asphalt mixtures

Statistical and optimization techniques are useful tools in understanding the interactions and relationships between the asphalt mix variables and the contribution of each variable to the resulting asphalt mixture properties. This study explores the response surface methodology to study the influence of steel slag and lime on the Marshall properties of asphalt mixtures using Box Behnken Design tool. The independent variables considered are steel slag (0-100%), lime (0-4%) and bitumen (4-8%). The stability, flow, Marshall quotients, bulk density, Vb and VMA obtained were 1.98-6.35 kN, 3.27-4.53 mm, 0.53-1.60 kN/mm, 2.08-2.29 kg/m3, 7.67-14.7% and 14.02-24.63%, respectively; indicating that the steel-slag and lime-modified asphalt mixtures satisfy the specification limits recommended by the asphalt institute and Nigeria General Specification for Roads and Bridges. The models' analysis of variance revealed could well predict the Marshall properties of the mixtures, and the terms of steel-slag, lime and bitumen content are significant. Likewise, based on the optimization analysis, 24.93% of steel slag, 2.43% of lime and 5.51% of bitumen content were selected as the optimal values for the modified asphalt mixtures. Additionally, a mean error of less than 5% was attained for all the responses, demonstrating the effectiveness of RSM in designing asphalt mixtures.

Effect of dry desulfurization ash as a filler on asphalt pavement performance

This study aims to explore the feasibility of using dry flue gas desulphurization ash (DFGDA) as a filler in asphalt pavements. Two DFGDA materials were added into the base asphalt with different mineral powder proportions to prepare asphalt mastic and mixture, and the pure mineral powder asphalt mastic and mixture were used as the blank control group to evaluate the properties of DFGDA-doped asphalt mastic and mixture. The results show that the addition of DFGDA can improve the high-temperature rheological property and reduce the low-temperature rheological property of asphalt mastic; similarly, the high-temperature stability of asphalt mixture can be greatly improved, while its low-temperature performance and water stability are reduced; despite these decreases, all outcomes still meet the requirements of relevant specifications. No chemical reactions are observed between DFGDA and asphalt, indicating that the physicochemical properties of fillers are responsible for the change in the properties of DFGDA-doped slurry and mixture. Notably, the DFGDA-added asphalt mixture does not bring additional negative effects to the environment. Based on cost analysis, the high-quality use of DFGDA in asphalt mixture can save direct material costs of about $920,000 per 100 kilometers of asphalt road construction. In summary, the application of DFGDA in the asphalt mixture can not only meet the basic performance requirements of asphalt pavements but also greatly save material costs and protect the environment.

Fracture characteristics of asphalt mixtures containing asphalt millings with geosynthetic fragments

The increasing cost of asphalt and environmental concerns have created a greater interest in exploring the possibility of incorporating higher percentages of reclaimed asphalt pavement (RAP) materials in asphalt mixtures. However, increasing the RAP content can adversely affect some of the properties of asphalt mixtures, including their cracking resistance potential. Consequently, finding a solution that accommodates incorporating higher RAP contents into the asphalt mixture is crucial. Moreover, geosynthetics has gained significant popularity as an anti-reflective cracking system in asphalt pavements, which may lead to the possibility of milling asphalt layers with geosynthetic interlayers. Thus, research studies need to be conducted to understand the characteristics and behaviour of RAP obtained from asphalt layers with geosynthetic interlayers (referred herein as GRAP). The objective of this study is to investigate the cracking characteristics of asphalt mixtures containing different percentages (0, 15, and 30%) of RAP and GRAP material using cross-shear tests. Results indicated that the addition of GRAP into the asphalt mixture by about 30% significantly improves the performance of asphalt mixtures against crack initiation and propagation compared to those asphalt mixtures containing only RAP. Overall, it can be inferred that the presence of geosynthetic fragments could increase the possibility of incorporating higher percentage of RAP in asphalt mixtures.

Enhanced stability of a three-dimensional graphene nanosheets networks modified asphalt mixture

To date, several concepts have been developed to enhance the mechanical and service life of asphalt pavements. Additives such as graphene, carbon nanotubes, carbon fibers and carbon black are used in the hot mix asphalt (HMA) or the asphalt binder (i.e., bitumen) for higher resistance to permanent deformations such as rutting, and transverse thermal cracking due to increased traffic volumes, vehicle mass and axle loads. In this study, graphene nanosheets (GNs) were used as potential modifier of bitumen binder in the HMA. The objective of this work is to investigate the impact of GNs modified bitumen on the Marshall stability and flow of the asphalt mixture using laboratory-compacted samples. The X-ray diffraction (XRD) study revealed a diffraction peak of GNs (002) at 2θ =26.5° along the bitumen’s γ-band and 10-band, which confirm a successful dispersion of GNs into bitumen binder. Furthermore, morphological analysis showed formation of a three dimensional (3d) interconnected networks of GNs between the bitumen micro-structures which could act as bridges for increased flexural strength of the binder. The Marshall stability and flow test results indicate that the mechanical properties of asphalt mixture were influenced by the addition of GNs to the bitumen binder. At 5% by weight of GNs modified bitumen (GNs-B), the compacted hot-mix Asphalt sample showed a higher Marshall stability of 11.7 kN recording 13.6% enhancement in comparison with the asphalt mixture with pure bitumen (P-B). In addition, when GNs-B was used, a lower flow of 1.4 mm was recorded which is desirable to prevent rutting and other forms of failure in asphalt pavements. This study underlines that adding GNs into asphalt binders such as bitumen could play a key role in enhancing the performance of asphalt pavements, which in turn extends their service life and saves maintenance expenses.

Aggregate gradation effect on the mechanical properties of asphalt mixtures

The issue of road deterioration in Mosul, Iraq, has become a matter of concern for local communities. The instability of road surfaces under the stress of vehicular traffic necessitates significant intervention to mitigate and manage this problem. This study has developed an asphalt mixture by following the Bailey method for aggregate gradation. The impact of aggregate gradation on the mechanical properties of the asphalt mixture was thoroughly analysed. Additionally, two separate mixtures were conducted using the conventional Marshall method to assess indirect tensile strength, Marshall properties, and susceptibility to moisture damage. The primary objective of this research is to design an aggregate structure that acts as a robust unit capable of withstanding heavy loads, repeated stresses, and high temperatures. The findings of the study indicate that the asphalt mixture created using the Bailey method exhibited superior stability with values of 13.6 kN, compared to the two traditional mixtures (11.8 kN, 9.2 kN), and. However, it is worth noting that the flow values also indicated a relative preference for the Bailey method, with values of and 3.1 mm, compared with 3.85 mm and 3.2 mm of the traditional mixtures. The results of Tensile strength ratio further corroborated the efficacy of Bailey’s technique, with outcomes of 85.1 %, thus enhancing the applicability of this method. This observation is attributed to the concept of granular interlocking, which forms the foundation of the Bailey method.

Deformation characteristics of asphalt mixtures

Asphalt pavement is among the most widespread road surfaces. For their design, assessment, and service life, it is necessary to evaluate the deformation characteristics of asphalt mixtures, which include the complex modulus of rigidity. Two-point (2PB-TR) and four-point (4PB-PR) flexural tests are used to determine these. The scientific paper focuses on the evaluation of the complex modulus as a function of varying temperature and frequency. The results of the study indicated that both methods provide significant information on the behaviour of asphalt mixtures under different loading conditions. Four-point bending may be more sensitive to changes in deformation properties than two-point bending. This finding is of fundamental importance when analysing the influence of different factors on the mechanical properties of asphalt mixtures. Measurements were performed at temperatures of 0°C, 10°C and 20°C and frequencies of 1 Hz, 5 Hz, 10 Hz, 15 Hz and 20 Hz. Validation of the different measurement methods was carried out on the comparison asphalt mix AC 11 O PMB 45/80-75.

Laboratory investigation on electrical and mechanical properties of asphalt mixtures for potential snow-melting and deicing pavements

This study aims to develop electrically conductive asphalt (ECA) mixtures utilizing carbon fiber and/or graphite for potential snow/ice-melting pavements without compromising the mechanical properties. The results showed that an electrical resistivity of 0.7–2.7 Ω·m could be potentially used as the design resistivity of ECA mixtures. 6 mm was the optimum length of carbon fiber for improving electrical conductivity. The ECA mixtures had a comparable or higher Marshall stiffness and indirect tensile strength than the control mixture. Adding carbon fiber alone significantly improved the cracking resistance of single-phase ECA mixtures, while the cracking performance of two-phase ECA mixtures was highly affected by the combinations of carbon fiber and graphite. Four ECA mixtures could meet the design resistivity requirement, while only one single-phase ECA mixture containing 6 vol% (by volume of binder) carbon fiber and one two-phase ECA mixture made with 3 vol% carbon fiber and 15 vol% graphite did not impair the cracking resistance.

Evaluating the low-temperature performance of asphalt mixtures based on the contraction and relaxation properties

The thermal cracking of asphalt pavement has been the focus of research in cold regions of the world. The contraction and relaxation properties of asphalt mixtures were crucial for investigating the thermal stress of asphalt pavement based on the thermal cracking mechanism. This paper proposed a novel evaluation index for characterizing the low-temperature performance of asphalt mixtures by considering their contraction and relaxation properties. Firstly, the rank during the evaluation indexes for low-temperature performance was determined by comparative analysis of method. Secondly, the thermal contraction coefficient was used to characterize contraction properties and cumulative stress at per unit strain rate (CSSR) was used to characterize relaxation properties in this paper. According to the cumulation process of thermal stress, a novel index was constructed based on the contraction and relaxation properties. Finally, considering the correlation between the failure temperature and the novel indexes, the prediction model of low-temperature performance consistent with the order of failure temperature was established based on the multiple linear regression method. Through the standardized analysis of the prediction model, the influence of novel indexes for the low-temperature performance of asphalt mixtures under different temperature conditions was clarified. A novel evaluation index provided a theoretical basis for unifying the evaluation indexes of asphalt mixtures.

Effect of aging on damping properties of rubberized asphalt binder and rubberized porous asphalt mixture

The purpose of the study is to explore the effect of aging on the damping properties of rubberized asphalt binder and rubberized porous asphalt mixture (RPAM), and to reveal the attenuation mechanism of damping properties. The effect of aging on the damping properties of asphalt binder was analyzed through temperature scanning test. Fourier transform infrared spectroscopy, gel permeation chromatography, and fluorescence microscopic test were conducted to analyze the aging mechanism of damping properties from the perspectives of chemical composition and morphology. The dynamic modulus test and free vibration damping test were used to investigate the effect of aging on the damping properties of asphalt mixtures. Results showed that aging led to a decrease in the damping properties of asphalt mixtures. Compared to porous asphalt mixture, RPAM had lower sensitivity to aging, so its damping properties was less prone to decay. The effect of aging on asphalt binders obtained from the temperature scanning test was consistent with the results of asphalt mixtures, indicating that the decrease in damping properties of asphalt mixtures was attributed to the deterioration of damping properties of asphalt binders. The results of chemical composition and phase morphology indicated that the proportion of large molecules in the asphalt binder increased significantly during the aging process. The decrease in intermolecular mobility led to a decrease in the damping properties of asphalt binder. Significantly, crumb rubber can prevent the aging of asphalt binder, thereby delaying the attenuation of damping properties of RPAM.

Effects of crumb rubber and styrene-butadiene rubber additives on the properties of asphalt binder and the Marshall performance properties of asphalt mixtures

The primary aim of this study is to evaluate the impact of incorporating crumb rubber (CR) and styrene-butadiene rubber (SBR) additives, ranging from 0% to 5% by weight of bitumen, on the performance of a bituminous concrete mixture using the wet process. Laboratory experiments, including the Marshall test, were conducted to establish the optimum bitumen content (OBC) for the hot mix. The study focuses on determining the optimal proportions of CR and SBR to achieve maximum strength. The results show that increasing the proportions of both CR and SBR leads to significant improvements in strength, with the maximum stability recorded at 16.14 kN and a flow of 1.23 mm for a mix containing 5% CR and 4% SBR. The findings further suggest an inverse relationship between CR content and strength, while an increasing SBR content enhances strength. Consequently, the optimal proportions for incorporating CR and SBR additives are identified as 5% and 4%, respectively.