Stress Creep Research Articles

Evaluation and comparison for higher temperature performance index of emulsified asphalt mastic using coal gangue powder

In order to investigate the rheological behavior and the influence of solid waste coal gangue powder on the high-temperature performance of cold recycled Emulsified Asphalt Mastics (EAM), Dynamic Shear Rheometer (DSR) and Multiple Stress Creep Recovery (MSCR) tests were conducted using three different fillers and four powder-to-binder ratios of EAM. Evaluation indexes such as rutting factor (G*/sinδ), improved rutting factor (G*/1−1/sinδ∙tanδ), Unrecoverable Creep Compliance (Jnr), Cumulative Strain (CS) and Creep Recovery Ratio (R) were used to analyze the influence of filler type and dosage on high temperature of EAM, and the effectiveness of these indexes to evaluate high temperature is considered. Moreover, atomic force microscopy experiments were carried out to study on interaction mechanism between the fillers and emulsified asphalt. Finally, grey relational analysis method was used for quantitative assessment of these indexes for EAM. The results indicate that all three fillers effectively improve the high-temperature performance, with a larger improvement observed as the filler dosage increases, among which the tunneling coal gangue powder is the most significant. Under a stress level of 0.1 KPa, the coal gangue filler mastic appears the best deformation recovery ability, whereas under a stress level of 3.2 KPa, the cement filler mastics appears the best deformation recovery ability. The additional fillers significantly influence the nano-scale surface morphology of the residues, and the tunneling coal gangue powder appears a stronger adsorption capacity for free polar components compared to the cement and limestone mineral powder. It is suggested that the Jnr and CS can be used as evaluation indexes of high temperature evaluation index of EAM, instead of G*/1−1/sinδ∙tanδ or G*/sinδ or R.

Effect of waste crab shell powder on matrix asphalt

Abstract In order to solve the problems of depleting petroleum asphalt resources and deteriorating pollution of marine products, a systematic study was carried out on the application prospect of waste crab shell (WS) powder as asphalt modifier. In this study, the physical properties of WS powder modified asphalt (WSA) were tested by blending different contents of WS powder into matrix asphalt; the high and low temperature rheological properties of WS powder modified asphalt were characterized by using Dynamic shear rheometer, Bending beam rheometer, and Multiple stress creep recovery test. In addition, the microscopic chemical properties and modification mechanism were analyzed by Differential scanning calorimetry, Fourier transform infrared spectroscopy, Atomic force microscopy, and Scanning electron microscope. It was shown that the WS powder enhanced the viscoelastic properties, temperature sensitivity properties, and permanent deformation resistance of asphalt. In addition, there was no obvious chemical reaction between the WS powder and the matrix asphalt, and no new chemical substances were generated; at the microscopic level, the WS powder and the matrix asphalt had good compatibility. In conclusion, the use of WS powder as a bio-based asphalt modifier to improve the resources and environmental issues have certain prospects.

Shear creep deformation of rock fracture distrubed by dynamic loading

The long-term stability of jointed rock masses is usually dominated by fault activation, which may be triggered by the dynamic disturbance generated by blasting during mining activities, leading to the occurrence of disasters such as landslides in open-pit and rockbursts in deep mining. The initial stress and dynamic disturbance are key factors that strongly affect the shear creep behavior of rock fractures. In this work, the shear failure instability of rock fractures of sandstone under creep-impact loading was experimentally investigated by using a creep-impact test machine, which allows for applying creep loading and an additional dynamic disturbance on rock fractures. Three stages of shear creep deformation, creep strain rate, and time-to-failure are examined under different creep stress levels and impact energies. Experimental results show that the tangential and normal creep rates increase with the increase of creep stress and impact energy, but the increment of tangential creep rate is higher than that of the normal creep rate. The time-to-failure of the creeping specimen is shortened under high creep stress and large impact energy, while the time-to-failure after the last dynamic disturbance of the specimen is determined by the total impact energy and creep stress level. By using high-speed photography, it is found that the failure types of rock depend on the magnitude of impact energy and creep stress level; that is, rock mainly slides with low stress levels and shears off with high stress levels. In addition, under different impact energy and creep stress levels, the variation of height is between 0.38 and 0.52, while the defined fracture factor, which describes the degree of failure of serrations, is between 0.30 and 0.54. The findings can provide deep insight into the fault sliding mechanism caused by mining activities, which provides theoretical support for the safe mining of ore in fault fracture zones.

Assessing pavement characteristics: An in-depth evaluation of waste engine oil and Buton rock asphalt composite modified asphalt and its mixture

To investigate the cooperative influence of waste engine oil (WEO) and Buton rock asphalt (BRA) on asphalt characteristics, the WEO/BRA composite modified asphalt and its mixture with varied dosages were prepared. The high-, moderate-, and low-temperature assessments of WEO/BRA composite modified asphalt were conducted through temperature sweep tests, multiple stress creep and recovery (MSCR), and bending beam rheometer (BBR) tests. The softening point difference was used to analyze the storage stability of composite modified asphalt. Based on the Fourier transform infrared spectroscopy (FTIR) and fluorescence microscope (FM) test, the microscopic feature and chemical constitution of WEO/BRA composite modified asphalt were analyzed. Rutting test, low-temperature bending test, immersed Marshall test, freeze-thaw splitting test, and four-point fatigue bending test were carried out to verify the pavement properties of the WEO/BRA composite modified asphalt mixture. The results indicated that WEO improved the capability in low-temperature conditions and fatigue properties of asphalt modified with BRA. BRA enhanced the high-temperature property of asphalt modified with WEO. The synergistic effect of WEO, BRA, and neat asphalt was a physical reaction, and these modifiers were uniformly distributed in the asphalt. Meanwhile, WEO/BRA composite modified asphalt had excellent storage stability for the single modified asphalt. The test results of the asphalt mixture verified the results, indicating that WEO/BRA composite modified asphalt can be considered a new green and durable asphalt pavement material.

Extraction solvents effect on asphalt binder properties

Asphalt industries are actively pursuing the integration of recycled asphalt pavement (RAP) into their constructions to promote sustainable pavement solutions amidst resource scarcity. However, challenges persist in the extraction and recovery processes, potentially affecting asphalt pavement performance assessments. This study investigates the impact of three common solvents—n-propyl bromide (nPB), trichloroethylene (TCE), and a toluene-ethanol blend (85 %/15 %)—on the rheological properties of recovered binders, particularly aiming to identify a substitute for TCE in light of its proposed ban by the Environmental Protection Agency (EPA) in the USA. Tests were conducted on six different performance-graded (PG) binders from diverse sources, assessing high-temperature properties using Dynamic Shear Rheometer (DSR) and Multiple Stress Creep Recovery (MSCR) tests, as well as low-temperature properties via Bending Beam Rheometer (BBR). Fourier Transform Infrared (FTIR) spectroscopy confirmed the absence of solvents in the recovered binders. Although minor variations were observed in measured properties between original and recovered binders due to solvent use, these differences did not affect the resulting performance grades. Thus, the toluene-ethanol blend can potentially substitute for TCE. However, it is noteworthy that the toluene-ethanol blend (85 %/15 %) displayed a slower solubility rate compared to nPB and TCE, underscoring the need for caution in its usage.

Creep rafting fracture and strain properties of overheating Co-based superalloy: Crystal plasticity phase-field simulation

The creep fracture and rafting of Co-based superalloys under thermal loading are critical properties for the long time working at high temperature, the crystal plasticity phase-field (CPPF) model is developed by incorporating the creep damage theory. The study of creep in Co-5Al-14V (at.%) superalloy in states of isothermal, continuous heating and overheating is realized. The rafting mechanism and evolution kinetics of γ′–Co3(Al, V) phase are analyzed in processes of directional coarsening and dissolution fracture under thermal loading stress, the incomplete P-type rafting morphology with low volume fraction of γ′ phase shows a reduced creep resistance. The creep strain has a steep rise for the rafting fracture and degeneration induced by overheating stress. The overheating followed by cooling triggers the recovery of γ′ rafts and improves the creep resistance. In addition, the dissolution and fracture of γ′ rafts are driven by the chemical potential, while the rafting and re-precipitation of γ′ phase are driven by the elastic potential under the creep stress. At the tertiary creep stage, the damage variable and creep strain increase in the order of isothermal creep, overheating and continuous heating. The studies show the creep fracture and strain properties in stress-diffusion mechanisms by coupling experiment morphology and CPPF simulation, the relationship of creep fracture and rafting properties of superalloys is established.

Functional and rheological investigations on hydrophilic nanoclay blended bitumen

Functional and rheological characteristics are two essential criteria for the success of any modifiers for the modification of bitumen. Recently, nanoclay has grabbed extensive attention as a key solution for enhancing the performance of bitumen. This study focuses on evaluating the dispersion, storage stability, high-temperature performance, and aging resistance potential properties of bitumen VG-30 modified with montmorillonite bentonite hydrophilic nanoclay (NC). Various proportions (0, 2, 4, 6, and 8% by weight of bitumen) of NC were blended with VG-30 using a high shear mixer (HSM). Various performance assessments, including kinematic viscosity by Brookfield Rotational Viscometer (BRV), multiple stress creep recovery (MSCR), high-temperature performance grade (PG), frequency sweep along with scanning electron microscopy (SEM) were conducted. SEM images and viscosity data analysis show that dispersion problem arises beyond 6% of NC addition while phase separation is in the acceptable range. Further, considerable increment in Superpave rutting parameter (G*/Sinδ) and recovery percentage (%R), and decrease in non-recoverable compliance (Jnr) was seen, resulted up to 30% improvement in rutting performance of the bitumen. Furthermore, the potential for aging resistivity resulted a significant drop in aging index (AI) values, suggesting that introducing NC to bitumen could significantly improve aging resistivity. Moreover, rheological approaches can be helpful to understand temperatures and frequency dependent aging behaviours of bitumen.

Determination of uniaxial creep properties using equivalent factors by sharp indentation

The uniaxial creep properties, including the creep coefficient and stress exponent, are crucial to characterize the creep behavior of materials. Instrumented sharp indentation test (ISIT) is a non-destructive technique to characterize the uniaxial creep properties using the stress equivalent factor and strain rate equivalent factor. However, the strain hardening exponent of tested material is ignored in the contact model, leading to inaccurate estimation of uniaxial creep coefficient. Based on finite element simulations, the effects of the strain hardening exponent on equivalent factors were investigated. The relationships between the equivalent factors, the strain hardening exponent, and the yield strain were established. Indentation and uniaxial tests on Pb95Sn5 and Sn99Cu1 were conducted to validate the established equivalent factors. Then those factors were used to determine the uniaxial creep coefficient of Pb95Sn5 and Sn99Cu1 by ISIT. This work demonstrates the feasibility of measuring uniaxial creep properties of work hardened material by ISIT.

Exploring the physicochemical and rheological properties of sustainable asphalt binders modified with lignin and high-viscosity additive

The primary objective of this investigation is to evaluate how the incorporation of lignin and high-viscosity modifiers impacts the performance of asphalt binders. Lignin-modified asphalt binder (LBA) and lignin-high viscosity modifier composite-modified asphalt binder (LHA) were created by blending 5 % and 15 % lignin, respectively. To understand the physicochemical interactions, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) were employed to analyze functional groups, thermal properties, and phase changes. Additionally, the linear rheological behavior and nonlinear rheological behavior were evaluated through frequency sweep and multiple stress creep recovery tests. The findings suggest that lignin blends physically with the asphalt binder and high-viscosity modifier without a chemical reaction. Although the onset pyrolysis temperature of lignin is significantly lower than that of asphalt binders, due to its relatively low content, the thermal decomposition of lignin-modified asphalt binders is primarily controlled by the asphalt binder itself and still exceeds the construction temperature. However, lignin incorporation increases the asphalt binder's glass transition temperature, potentially affecting low-temperature performance. Lignin significantly enhances the modulus in the high-frequency region of both unmodified and high-viscosity modified asphalt binder. However, it has a negative effect on the modulus in the low-frequency region of high-viscosity modified asphalt binder. Furthermore, nonlinear creep recovery test results demonstrate that lignin positively contributes to the deformation resistance of unmodified asphalt binder in a content-dependent manner, whereas it reduces the elastic behavior and deformation resistance of high-viscosity modified asphalt binder. In addition, low levels of lignin increase the stress sensitivity of binders, while high levels of lignin decrease it. Despite these effects, the performance of lignin and high-viscosity additive composite-modified asphalt binder remains superior to that of unmodified asphalt binder. These findings offer valuable insights into the combined use of lignin and polymers in asphalt binder modification.

Waste coffee biochar and bi-oil composite modified rejuvenated asphalt: Preparation, characterization, and performance evaluation

In the realm of sustainable road construction, bio-oil has emerged as a promising and eco-friendly alternative for rejuvenating aged asphalt. Nevertheless, challenges arise due to poor stability, diminished performance at elevated temperatures, and limited anti-aging properties. This study introduces an innovative approach by blending biochar, obtained from the pyrolysis of waste coffee grounds, into bio-oil to create a composite modified regenerator. Initially, the study conducts a microscopic characterization of the biochar using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Subsequently, the rheological properties of this composite rejuvenated asphalt are evaluated across low, moderate, and high-temperature ranges using bending beam rheometer (BBR), linear amplitude sweep (LAS), and multiple stress creep and recovery (MSCR) tests. Departing from the traditional emphasis on initial property restoration, it further delves into performance alterations after re-aging of rejuvenated asphalt through temperature sweep (TS) and Fourier transform infrared spectroscopy (FTIR) tests, providing a comprehensive assessment of the anti-aging characteristics of rejuvenated asphalt. Additionally, gel permeation chromatography (GPC) is employed to quantitatively analyze the changes in asphalt molecular weight distribution. The microscopic characterization reveals the development of a rough and porous structure within the biochar, facilitating enhanced adhesion and interaction between the rejuvenator and the asphalt binder. Moreover, bio-oil rejuvenated asphalt exhibits excellent low-temperature crack resistance and moderate-temperature fatigue resistance. Following the incorporation of biochar, notable enhancements in high-temperature rutting resistance and anti-aging properties are observed, validating the efficacy of the biochar with bio-oil composite modified regenerator. To achieve optimal performance outcomes, a biochar content of 6 % (as a proportion of aged asphalt), corresponding to a 1:1 ratio of biochar to bio-oil, is recommended. Under this condition, the properties of the composite modified rejuvenated asphalt demonstrate comparability to those of the original asphalt. In summary, this research underscores the potential for integrating waste coffee biochar material into infrastructure development, thereby promoting circular economy principles and advancing more sustainable construction practices.

Structural response of glass fiber-polymer composite bending-active elastica beam under long-term loading conditions

Bending-active elastica beams represent structural members which are initially installed as straight beams and then bent into arched shapes by applying horizontal displacements to one support. Designing such members for permanent structures made of fiber-polymer composites involves complex viscoelastic responses, which have not yet been thoroughly investigated. An experimental investigation of medium-scale bending-active elastica beams, consisting of pultruded glass fiber-polymer composite profiles, was thus conducted to investigate the long-term structural behavior of such members under imposed sustained bending and axial compression. The results revealed that viscoelastic responses are based on an interaction of stress relaxation and creep with their effects increased with increasing bending degree and time of exposure to sustained strains and stresses. The imposed horizontal displacement to one of the supports to maintain the bent beam shape induced sustained bending stresses in the beam. Beneficial relaxation of these stresses occurred with relaxation predicted to reach 12 % during a targeted 50-year design service life. Furthermore, the likelihood of the curved beam exhibiting in-plane deformations under sustained stresses enabled creep to occur simultaneously, with associated in-plane creep deformations and strength reduction. While creep deformations remained insignificant, progressive creep rupture occurred at highest bending degrees, exhibiting sequential creep rupture in the outer combined mat layers, delamination, crack opening and final fiber failure. Creep rupture can be prevented by postponing crack initiation in the combined mat layer beyond the targeted design service life. This can be achieved by limiting the bending degree to 50 % of the bending degree at which short-term crack initiation occurs.

Creep stress analysis of Transversely Isotropic Rotating Disc Composed of Piezoelectric Material

If a crystal undergoes mechanical stress, then an electrical potential is developed across its sides; this phenomenon is called piezoelectricity, or the piezoelectric effect. Piezoelectric materials include quartz, zinc oxide (ZnO), lead zirconate titanate (PZT4), and Rochelle salt. There are numerous uses for piezoelectricity in signal and electrical transducers. In this work, transitional and creep stresses are evaluated in a thin disc made up of piezoelectric transversely isotropic solids subjected to rotation. The mathematical expressions of stress components are computed for the rotating disc by using Seth’s transition theory considering the rotation effect in circular disc. The electric displacement relations and various stress components are computed using Hooke’s Law. A non-homogeneous differential equation is obtained by using mathematical relations and the equilibrium equation. The theoretical solution of the differential equation is obtained under specified boundary conditions. Creep stresses are studied for the considered material. The obtained results are shown graphically, analyzed numerically, and concluded with a discussion of the results for transversely isotropic piezoelectric materials such as BaTiO3 and PZT-4, among others. On the basis of all the numerical discussions and graphs, it is concluded that discs composed of transversely isotropic piezoelectric (PZT4 and BaTiO3) materials are more stable than discs composed of transversely isotropic (magnesium and beryl).

Rheological and mechanical evaluation of a novel fast curing cold asphalt concrete made with asphalt emulsion, by-products and magnetic induction

This work studies the feasibility of a new cold asphalt concrete with 5 % voids with fast curing, developed with asphalt emulsion and magnetic induction. Until now, it was impossible to produce fast curing cold asphalt concretes due to the impossibility of compacting and evaporating the water in the asphalt emulsion quickly. Therefore, the aim of this work is to solve the impossibility of compacting the cold asphalt concrete and thus reduce the long curing times. For this purpose, at laboratory level, an experimental cold asphalt concrete was designed with magnetic induction and compared with two reference hot asphalt concretes manufactured according to Spanish standards without magnetic induction (one with 50–70 grade bitumen and another with a PMB45/80–65 type polymer-modified bitumen). The research was carried out in two stages. First, the new cold asphalt concrete was rheologically characterized, the binder recovered from the asphalt concrete was analyzed according to the tests of ring and ball, penetration, dynamic shear rheometer (DSR) and multiple stress creep and recovery (MSCR). Secondly, the new cold concrete asphalt was mechanically characterized, the mechanical performance of the cold asphalt concrete was analyzed by evaluating stability and deformation, dry and wet indirect tensile strengths (ITS), wheel tracking test, stiffness modulus and resistance to raveling dry and wet conditions. Based on the rheological analysis results, the asphalt emulsion recovered from the cold asphalt concrete is extremely soft with a low softening point and a high penetration rate. On the other hand, the values of viscosity, phase angle, stiffness and non-recoverable creep compliance are between those of the bitumen 50/70 and the PMB45/80–65, but closer to bitumen 50/70. As for their mechanical performance, the novel cold asphalt concrete studied presents better resistance to water damage and particle loss, both in dry and wet conditions, but also high permanent deformations and low ITS, probably due to the fact that the residual binder of the emulsion used is softer than the others.

Development of SBS composite modified asphalt incorporating polydopamine-enhanced MoS2

This study investigated the development of a novel composite modified asphalt incorporating PDA-MoS2 into styrene-butadiene-styrene (SBS) modified asphalt. The successful synthesis of PDA-MoS2 was confirmed through various characterization techniques. The incorporation of PDA-MoS2 into SBS modified asphalt resulted in significant improvements in performance properties. With a PDA-MoS2 content of 0.7 wt%, the modified asphalt showed a notable 15.1% rise in softening point and a 24% drop in penetration in comparison to the control SBS modified asphalt. Dynamic Shear Rheometer tests revealed a 2.4-fold increase in the rutting factor at 60°C. Multiple Stress Creep Recovery tests demonstrated enhanced rutting resistance, with a 72.2% reduction in nonrecoverable creep compliance at 0.1 kPa stress level. Electrochemical measurements showed improved corrosion resistance, evidenced by lower current densities and higher charge transfer resistance. Microstructural analysis revealed well-dispersed PDA-MoS2 particles forming a compact network structure within the asphalt matrix. The hydrophilicity of the modified asphalt increased, with a 35.3% decrease in water contact angle. The synergistic effect between PDA-MoS2, SBS, and asphalt components, facilitated by enhanced interfacial interactions and chemical bonding, contributed to the observed performance improvements. The results indicate that PDA-MoS2 has the potential to improve the characteristics of SBS modified asphalt as a modifier.

A novel Ta-contained TiAl alloy with excellent high temperature performance designed for powder hot isostatic pressing

TiAl alloys offer strong potential for replacing conventional nickel-base alloys in structural applications at high temperatures, which requires good high temperature performance. This study analyzes the creep performance and thermal exposure characteristics for a powder hot isostatic pressing (P-HIP) Ta-contained TiAl alloy. The microstructure characteristics, creep performance, and thermal exposure properties of the nearly lamellar (NL) alloy with a size of about 145 μm were investigated. The alloy remains 0.72 % fracture strain at room temperature after exposure at 750 ℃ for 1000 h. The fitting results of creep curves show that the creep stress index n is 15.82 at 750 ℃, indicating the power law creep mechanism. By reducing the interfacial energy, Ta can facilitate the formation of metastable structures and achieve refinement. The enrichment of Ta element at the lamellar edge, both observed after thermal exposure and creep, inhibits the growth of lamellae and hinders the expansion of cavities due to its low diffusion rate, improving the thermal stabilities and creep performance. The P-HIP Ta-contained TiAl alloy shows exciting high temperature performance.

Creep stress induced pit-to-crack transition of Super304H in fireside corrosion

Parallel experiments on creep-rupture and corrosion of Super304H were conducted at 650 ℃ in a simulated ultra-supercritical fireside environment to study the impact of creep stress on fireside corrosion. The corrosion products, corrosion pits, grain structure and phase composition, and surface cracks of creep-corrosion and corrosion samples were compared. Results show that stresses not only affect the formation and growth of corrosion products, but also widen the recrystallization zone in corrosion affected area. A model of surface cracking from corrosion pits under the synergy of fireside corrosion and creep stress was proposed.

Viscoelastic behavior of warp-knitted spacer fabrics in iterative compression and decompression

In this study the viscoelastic behavior of warp-knitted spacer fabrics was investigated for compressional deformation. The fabric specimens were tested via loading and unloading time intervals under predetermined conditions. Following the upside tests, specimens were relaxed for 24 h to examine the recovery prior to completing the downside tests. The data obtained from the compression and decompression cycles were examined for stress relaxation and creep through stress–time plots. From the results it was observed that, despite the non-homogeneous structure of the spacer fabric, the specimens demonstrated exponentially changing behavior within the given time intervals. Since the response of fabrics to compression and decompression cycles can be expressed as a function of time, a mathematical approach was expressed in accordance with the time-dependent behavior of the fabrics regarding the monofilaments as bent beams. The responses of the fabrics to the experimental set up conditions were evaluated to determine the potential usage performances of the fabrics. Fabric thickness, number of monofilament yarns in the structure, and thickness of the monofilaments had the major effects on the performance of the fabrics. Future research could consider modeling studies to predict usage performance, and tailoring the fabrics before production.

Sewage sludge ash as filler in asphalt mastic: Low-temperature towards high-temperature performance

The sewage sludge ash (SSA) is characterized as a by-product used in the pavement industry to mitigate the environmental risks, enhance the landfill capacity and conserve the non-renewable resources. This research utilized SSA as a filler substitute in asphalt mastic, and its performance-based properties from low towards high temperatures were evaluated. For this goal, the physical and chemical properties of SSA and rock powder (used as base filler) were determined using BET surface area measurement, X-ray fluorescence, and scanning electron microscopy tests. The performance of base and SSA-modified asphalt mastics in four filler/bitumen weight ratios (0.6, 0.8, 1, and 1.2) was investigated using dynamic shear rheometer, multiple stress creep and recovery, linear amplitude sweep, and bending beam rheometer tests across a wide temperature range. The results indicate that SSA has a higher specific surface area, better bitumen absorption, and lower density compared to the base filler. Additionally, unlike the acidic nature of the base filler, SSA possesses strong basic properties, leading to a stronger chemical bond with bitumen and enhanced resistance to aging, particularly at high temperatures. Moreover, the lower density of SSA escalates the amount of filler per unit volume of the SSA-modified asphalt mastic, leading to the increased stiffness and elasticity. This trend improves resistance to permanent deformation and cracking at medium temperatures, although it has an adverse effect on performance of mastic at low temperatures. Moreover, due to the improved performance of SSA-modified asphalt mastic, this study can contribute to the sustainable development of the pavement industry.

A comparative study into the effect of spent coffee powder and ash on improving the mechanical properties of bitumen

Nowadays, waste and renewable materials are used to modify bitumen and asphalt, reduce costs, decrease the use of natural resources, and maintain ecological balance, and have thus received much attention. This study aimed to improve the rheological properties of bitumen and reduce spent coffee grounds' (SCG) waste by partially replacing it with SCG powder and ash. SCG powder and ash were added in percentages of 0, 1, 3, 5, and 8 wt percent of bitumen to check the properties of control and modified bitumens. Microstructural properties were evaluated by Fourier transform infrared spectroscopy, thermal gravimetric analysis, X-ray fluorescence spectroscopy (XRF), and scanning electron microscopy (SEM). Penetration, softening point, and ductility tests were performed to check the physical properties of bitumens, along with the storage stability test. Rheological tests (viscosity, bending beam rheometer (BBR), dynamic shear rheometer (DSR), multiple stress creep and recovery (MSCR), and linear amplitude sweep (LAS) were also carried out. According to the BBR results, adding SCG powder up to −12 °C and adding SCG ash up to −6 °C increased the resistance to low temperatures. Based on DSR and MSCR results, SCG, either in the form of ash or powder, increased the resistance to rutting, and adding SCG ash improved the high temperature performance of bitumen by 1 grade. At 64 °C, adding 8 % of SCG powder increased the rutting resistance by 43 %, and adding SCG ash raised the rutting resistance by about 113 %. LAS results also showed that SCG ash outperforms SCG powder in fatigue. Although both SCG powder and ash performed well in high, moderate, and low temperatures, SCG powder performed better in cold regions, and SCG ash performed better in regions with temperate and tropical climates.

Performance Characterization of the Field Aged Asphalt Pavement Materials at Mortar Scale: Testing Method Optimization and Rheology Analysis

Performance evaluation at the asphalt mortar scale offers increased sensitivity to aging and is less affected by extraction processes comparated to asphalt mixture. Despite these benefits, there is currently a lack of standardized methods for directly processing mortar samples obtained from field mixtures. This study aims to improve and validate a manufacturing procedure for aged mortar specimens derived from field aging cores, and to evaluate the field damage level of asphalt paving materials at the mortar scale. A novel approach was developed that incorporates warm sieving, compaction, coring, and cutting to manufacture mortar specimens suitable for Dynamic Shear Rheometer (DSR) tests. This study selected mortar specimens with different service ages and conducted rheological tests, including frequency sweep tests and modified Multiple Stress Creep Recovery (MSCR) tests, to assess their rheological performance. And the significance test of all the indcies were conducted to select suitable indcies.The results show the proposed aged mortar manufacture approach can prepare eligible mortar specimens for rheology tests. The rheology test results show that several indices can distinguish different mortar types and service ages, and the indices of surface layer mortar follow a linear relationship with service age. The linear viscoelastic zone (LVE), representative shear modulus (G0), and unrecovered creep compliance at 1.6kPa (Jnr1.6) and 3.2kPa (Jnr3.2) are identified as effective indices for evaluating the behavior of field aged mortar because of their effectiveness, lower variability, and better distinction.