Effect Of Long-term Aging Research Articles

Investigation of the Wet and Thermal Conditions Effect on the Micro-Scale Characteristics of Interfacial Transition Zone of Porous Asphalt Mixture

Complex environmental factors can significantly influence the micro-properties of porous asphalt (PA) mixture. Therefore, the effects of short-term and long-term thermal aging and moisture immersion on the micromechanics properties, micro-morphology, and chemical element distributions of the interfacial transition zone (ITZ) of PA mixture were studied to reveal the mechanisms by which environmental degradation impact performance by means of nanoindentation (NI), backscattering scanning electron microscope (BSEM), and energy-dispersive X-ray spectroscopy (EDS) analysis techniques. The results show that the ITZ is not the softest part of the PA mixture, and the order of modulus is aggregate > ITZ > asphalt mastic. ITZ thickness is about 10–20 μm. Thermal aging has negligible effect on the width of ITZ. With increasing aging degree, the asphalt mastic and ITZ modulus increase, while water damage reduces the modulus of ITZ and slightly increases the width of ITZ. Thermal aging has little effect on the morphology of ITZ, while water damage will lead to microcracks and micropores in ITZ. Compared with thermal aging, water damage has a greater effect on the morphology of ITZ and leads to softening of the interfacial transition zone and asphalt mastic phase. The width of ITZ obtained by EDS line scanning is basically consistent with that of nanoindentation. Overall, external environmental factors have a more significant effect on the mechanical properties than the micro-morphology of ITZ. The outcomes of this research provide a better understanding of the impact of the service environment on the microscopic characteristics of PA mixture.

Effect of microstructural evolution and mechanical properties of Haynes 230 superalloy during long-term aging at 700 °C

The effect of long-term isothermal aging of Haynes 230 super-alloy in an advanced ultra-supercritical (A-USC) power plant at 700 °C for up to 10,000 h on microstructural evolution and tensile behavior. And utilizing a combination of the scanning electron microscope (SEM), X-ray diffraction analysis (XRD), and transmission electron microscope (TEM). Although the grain size and grain boundary M23C6 carbides did not change significantly, the dissolution of intercrystallite primary M6C carbides and the precipitation of intracrystalline secondary lamellar M6C carbides were observed at 2000 h to 10,000 h. According to the SEM and TEM results, it is shown that the dissolution of primary M6C carbides makes the W, Mo, and Cr in the γ matrix increase, while the precipitation process of secondary M6C carbides is M+ 6 C→M6C. To reduce the interfacial energy of the γ matrix, secondary M6C carbides are precipitated in the crystal under long-term aging at 700 °C, with a gradual increase in time content. the best tensile and yield strengths at 750 °C occur after 4000 h of aging, with microscopic voids forming mainly around the granular M6C carbides in the crystal, but the solid solution strengthening effect of the matrix provides the strength. The worst strength and elongation occur after 10000 h aging, when the dissolution of granular M6C and secondary precipitation of M6C carbides are most abundant, interfacial cavity formation of granular M6C carbides and brittle fracture of M6C carbide particles, and the growth of non-co-grained secondary M6C carbides with the matrix allow more microscopic cavities to appear during high-temperature tension, reducing the strength of Haynes 230 and plasticity.

Evaluation of field aging effect on self-healing capability of asphalt mixtures

Asphalt mixtures have the potential to repair a part of their cracks through self-healing capability. However, various factors, such as aging, can influence the effectiveness of this phenomenon. In this respect, it is very important to consider the real effects of field aging. Therefore, this study investigated the effects of long-term field aging on the self-healing capability of asphalt mixtures. For this purpose, three asphalt pavement sections with similar mix designs and service life of 7, 10, and 11 years were studied through Fourier transform infrared spectroscopy (FT-IR). Then, the middle part of the asphalt layers was core-drilled, and their self-healing capability was evaluated using Semi-Circular Bending (SCB) test. The samples were healed using heating in a forced draft oven at three temperatures of 35, 60, and 85℃ for 8, 16, and 24 h. Also, the three-point beam bending test was used to examine the effects of aging on the self-healing capability in the thickness of the asphalt layer. The results showed that the self-healing ability of asphalt can be influenced by the aging changes in its layer thickness. The asphalt samples with a service life of 11 years exhibited a difference of about 10 % between the surface’s self-healing index and the layer’s depth index. In addition, it was seen that the self-healing index of the middle part of the asphalt layers in the period of 7 to 11 years was almost constant and equal to 35 %. Based on the obtained results, it can be concluded that the changes in the Carbonyl Functional Group Concentration (CFGC) were directly associated with the changes in the self-healing ability of asphalt pavements in its thickness due to aging. Therefore, CFGC can be used as an indicator to estimate the self-healing capability of asphalt mixture in the depth of pavement layers.

Evaluation of effects of short and long-term thermo-oxidative aging on chemo-rheological and mechanical properties of asphalt concretes

The effects of short and long-term thermo-oxidative aging on stripping resistance, rut depth, stiffness modulus, fracture and fatigue resistances of asphalt concretes have been assessed. A modified RILEM thermo-oxidative aging procedure on loose asphalt mixtures has been used to evaluate the gradual evolution of these properties with the aging duration. Two short-term aging durations (4 and 8 hours at 135C) and three long-term thermo-oxidative aging durations (3, 6 and 9 days at 85C) and a reference mixture (0 day aging) have been considered to this end. The impact of long-term thermo-oxidative aging on the chemo-rheological properties of recovered asphalt binders have been investigated. At the binder scale, the results show an increase in the Fraass temperature, the softening point, the shear modulus , the aging index (AI= + ) and a decrease in the penetration grade with the aging duration. Some correlations between the viscoelastic transition parameters (, and ) of the recovered asphalt binders and the aging index have been established. At the mixture scale, the results show that the stiffness modulus () increases with the aging duration, while the index of fracture resistance (IFR), the stripping resistance (), the rut depth (P) and the fatigue deformation () decrease with the aging duration. Finally, some correlations between the aging index and the rheological and the mechanical properties of binders and concretes (, , P, IFR, ) have been proposed.

Aging and temperature effects on the dynamic characteristics of asphalt mortar under impact loading

Asphalt pavement structures are subjected to impact loading during the milling process. This study aims to investigate the dynamic behavior of asphalt mortar under high strain rates ranging from 281.7 to 830.3 s−1 through the Split Hopkinson Pressure Bar (SHPB) experiments. The effects of temperature and long-term oven aging on the dynamic properties of asphalt mortar under impact loading were statistically analyzed. The results indicated that the dynamic strength and the impact toughness are both enhanced with the increase in the strain rate and temperature. Laboratory oven aging of asphalt mortar at 85 °C for 72 h indicates a significant increase in the carbonyl and sulfoxide indices, a decrease in compressive strength, and rising in elastic modulus. The failure patterns show a strong correlation with the strain rates. An increase in the temperature produces a better gradation of the fragments at higher strain rates regardless of the aging state.

Antiaging Effects of Linear Alkyl Benzene Sulfonic Acid Utilization on Bitumen Modification

The manufacture of asphalt pavements causes various environmental problems due to bitumen’s hazardous nature. Aging of bitumen yields undesirable properties, which may cause several adverse effects on asphalt performance. Use of antiaging agents for bitumen modification results in improved aging resistance, hence such agents confer environmental benefits by reducing the consumption of bitumen owing to lower maintenance requirements and the reduced volume that needs to be produced. Therefore, it is important to develop new antiaging agents and investigate their benefits to the asphalt industry. This study investigated the use of different rates (1%, 2%, and 3%) of linear alkyl benzene sulfonic acid (LABSA) as a bitumen antiaging agent through chemical and rheological characterization on unaged, short-term-aged, and long-term-aged samples using Fourier transform infrared spectroscopy and dynamic shear rheometer (DSR). A chemical aging index (CAI) and various rheological aging indexes, obtained by the construction of master curves and crossover temperatures were calculated to evaluate the variation of aging effects by LABSA addition. The detailed experiments showed that LABSA-modified samples exhibited better aging resistance compared to neat (base) bitumen. Additionally, the statistical analyses of all aging indexes were investigated to obtain the relationship between chemical and rheological aging indexes. The determination coefficient (R2) and scatter index (SI) results showed that the rheological behavior of bitumen against aging could be evaluated based on chemical behavior and vice versa. Moreover, it was concluded that short-term aging and long-term aging effects should be evaluated separately to determine the relationship between different aging characteristics of samples.

Assessing the effect of short and long-term aging on moisture damage of hot mix asphalt using two different methods

ABSTRACT The effects of short-term aging (STA) and long-term aging (LTA) on moisture damage mechanisms were investigated using mechanical and thermodynamic methods. PG58-22 and PG64-16 asphalt binders modified with Dodecylamine (DA) and Wetfix (WT) additives and limestone and granite aggregates were used. The moisture sensitivity was assessed using the indirect tensile strength (ITS) test via the modified Lottman test and the surface free energy (SFE) method. As asphalt binder becomes harder due to aging, ITS values increase in dry conditions. However, ITS values decrease due to the texture and mineralogical properties of aggregates, the reduction of mastic cohesion and asphalt binder-aggregate adhesion because of water infiltration and weakening of the mixture in wet conditions. The tensile strength ratio (TSR) test revealed that TSR values decrease due to aging. The cohesion free energy of the PG64-16 asphalt binder increased by 8.9% in the STA state and by 29.8% in the LTA state compared to the unaged state. This rise in PG58-22 was about the same as that in PG64-16. Asphalt binder aging in all the samples reduced the adhesion energy. These variations indicated that aging reduces the probability of cohesion failure and increases the probability of adhesion failure.

Aging behavior of Ni-Mn-Ga/silicone particulate composites exhibiting large recoverable magnetostrain

Single crystalline Ni-Mn-Ga particles/silicone composites are new ferromagnetic shape memory materials, exhibiting a large reversible magnetic field induced strain (MFIS), are greatly demanded for actuators and sensors toward future technologies. In the present work, we studied a long-term aging effect on the mechanical and recoverable MFIS properties of the Ni-Mn-Ga/silicone particulate composites containing different amounts of filler. It was shown that despite a strong decline of the effective stiffness of pure silicone during long aging, the stiffness reduction of composites was much less pronounced and barely affected the characteristics of the large recoverable MFIS.

Aging phenomenon in low molybdenum Fe-21Cr-5Mn-1.5Ni alloy: Microstructure evolution, texture development and corrosion behavior

In the present work, the effect of long-term aging at 750°C up to 480 hours on microstructure evolution, texture development and corrosion behavior of a low molybdenum Fe–21Cr-1.5Ni–5Mn alloy has been investigated systematically. An increase in aging time results in increase in proportion of σ-phase. The σ-phase formation took place by the eutectoid decomposition reaction: δ → σ + γ 2 . The σ-phase did not show any specific orientation relationship with neighbouring δ ferrite grains. The initial solution annealed sample showed the presence of strong Brass ({110}<112>), Cube ({100}<001>), Goss ({110}<112>), and minor Cu ({112}<111>) in austenite, and strong γ-fiber (normal direction, ND//<111>) along with minor α-fiber (rolling direction, RD//<110>) in ferrite. After, long-term aging up to 480 hours, austenite showed strong Cu ({112}<111>) and minor Brass ({110}<112>) along with Cube ({100}<001>). Ferrite, on the other hand, showed γ-fiber. The lower amount of Cr/Mo and higher N in Fe-21Cr-1.5Ni-5Mn alloy was not enough to avoid the σ precipitation, however, it delayed its precipitation. The increase in σ-phase with aging time resulted in a decrease in corrosion resistance.

Effect of Long-Term Aging on the Tensile Strength, Flexural Strength and Creep Behaviour of Asphalt Mixtures Containing Different WMA Additives

Effect of Long-Term Aging on the Tensile Strength, Flexural Strength and Creep Behaviour of Asphalt Mixtures Containing Different WMA Additives

Effect of Long-Term Aging on Polymer Degradation and Fatigue Resistance of Hybrid Polymer-Modified Bitumen

Binder aging significantly affects the overall performance of asphalt pavements. For polymer-modified bitumen (PMB), this complex phenomenon is attributed to both polymer degradation and bitumen aging. This study aims to analyze whether the aging of hybrid PMB—combining styrene-butadiene-styrene (SBS) and recycled linear low-density polyethylene (RLLDPE) from waste plastic—is a result of bitumen aging, polymer degradation, or both aspects simultaneously. To further understand the aging process as a function of time, five different PMBs were subjected to long-term aging simulation using a pressure aging vessel (PAV) at three different durations (20, 40, and 60 h). SBS and RLLDPE (polymers only) were also aged under similar conditions, in order to isolate the polymer degradation from the bitumen aging. Tensile strength tests revealed that SBS is susceptible to polymer degradation and improves its elastic response as a result of aging. However, the tensile test results did not indicate whether RLLDPE underwent degradation. Results from the thermal analysis showed that RLLDPE did not significantly change the thermal events as the aging progressed. Hence, RLLDPE is assumed to have minimal degradation when subjected to long-term aging. Infrared spectroscopy results indicated that SBS underwent degradation, with aging promoting carbonyl formation, which is associated with bitumen hardening. Rheological results indicate that bitumen aging, due to thermal oxidation, is dominant compared to polymer degradation; as such, polymer degradation has minimal effects upon bitumen hardening.

Effects of Long-Term Aging on Properties and Laves Phase Evolution of A New Type of Fe-Based Superalloy

Effects of Long-Term Aging on Properties and Laves Phase Evolution of A New Type of Fe-Based Superalloy

Simulated Aging of Metal Tritides by Ball Milling Induced Gas Incorporation

The study of tritium aging effects on materials requires a significant time commitment as a consequence of its 12.3-year half-life, making developmental studies prohibitively difficult and expensive. However, detailed knowledge of long-term aging effects is critical to the development of structural and storage materials for future fusion reactor technologies. As a result, multiple approaches to simulated aging effects have been investigated. We report a method of simulated tritium aging achieved though the incorporation of trapped gases via high-energy ball milling of LaNi4.25Al0.75 alloy storage material. Experimental results verify the presence of trapped gases by a combination of temperature programmed desorption and LECO chemical analysis. Following gas incorporation, we find that many of the degraded hydrogen sorption properties found in aged storage materials are reproduced by the ball milled powders.

The Effect of Long-Term Ageing at 475 °C on Microstructure and Properties of a Precipitation Hardening MartensiticStainless Steel

The effect of long-term ageing (1000, 2000, and 3000 h) at 475 °C on mechanical properties, microstructure, and substructure of CUSTOM 465® maraging stainless steel was studied. The additional precipitation of nanometric particles of η-Ni3Ti phase in partly recovered lath martensite and decomposition of the BCC solid solution accompanied by the formation of nanometric Cr-rich α’particles were identified. The fraction of reverted austenite in the final microstructure gradually increased with time of ageing at 475 °C. Ageing resulted in a gradual slight decline (up to 10%) in yield strength, ultimate tensile strength, and hardness. On the other hand, for all ageing, dwells ductility and impact energy values remained almost unchanged. The reason for this phenomenon lies in the gradual increase in the fraction of reverted austenite during long-term ageing at 475 °C and at the same time in the sluggish kinetics of microstructural changes in lath martensite. No susceptibility to 475 °C embrittlement was proved.

Unraveling the Effect of Long-Term Aging on Hydrogen-Aided Cracking Behavior in a Maraging Stainless Steel

Unraveling the Effect of Long-Term Aging on Hydrogen-Aided Cracking Behavior in a Maraging Stainless Steel

Effect of Long-Term Aging on the Behavior of Batu Pahat Soft Clay-Modified Asphalt Mixture

Aging in the field is significantly influenced by the initial voids in the asphalt mixture, the intensification of the asphalt mixture under traffic, and the amount of heat applied to the mixture during production. Hence, this research is used to evaluate the effect of long-term aging on the behavior of soft clay-modified asphalt mixture. This study aims to evaluate the usage of soft clay powder, as a newly introduced material in asphalt mixture. Indirect tensile strength, indirect resilient modulus, and dynamic creep tests were conducted to determine and evaluate the performance of samples mixed using the Superpave system. The results obtained were perceived to be successful. As for the indirect tensile strength, the addition of batu pahat soft clay contributes to increasing the indirect tensile strength, especially when it was observed by using 4%, which gave better results than other soft clay percentages. In the resilient modulus test, Batu Pahat soft clay particles improved the fatigue and rutting resistance by 10.04%. While; in the dynamic creep test, the 4% soft clay value gave the best performance of evaluation works when it was conducted in a long-term aging process with the value of 0.14mm. More importantly, the evaluation of aging conditions noted that soft clay could resist and delay aging, promoting pavement durability. Also, this study was conducted to determine the most suitable and optimum patu pahat soft clay particles in the asphalt mixture and expectant to produce a new road material and to contribute toward producing cheap and effective asphalt mixtures for road construction

Assessment of the Aging Process of Finished Product–Modified Asphalt Binder and Its Aging Mechanism

Styrene-butadiene-styrene-modified asphalt binder (SBSMA), crumb rubber–modified asphalt binder (CRMA), and high-viscosity-modified asphalt binder (HVMA) have been widely used in porous asphalt concrete. However, the aging of the modified asphalt binder significantly affects the performance of the porous asphalt concrete. The main aim of this research is to quantitatively assess the aging degree of finished product–modified asphalt binders of SBSMA, CRMA, and HVMA at high, medium, and low temperatures, and to explore the aging mechanism at the microscopic level. This study used rolling thin-film oven and pressurized aging vessel to simulate the aging of asphalt binders. Dynamic shear rheometer, bending beam rheometer, Fourier transform infrared spectrometry, thin-layer chromatography with flame ionization detection, and scanning electron microscopy were employed to investigate how aging affects the rheological and microscopic properties of finished product–modified asphalt binder. The results showed that at high temperatures, short-term aging significantly impacted HVMA [change rate of the rutting factor (CRRF)=18.9%], while long-term aging had an enormous influence on CRMA (CRRF=179.5%). Short-term aging had the greatest effect on the fatigue property at medium temperature of CRMA [change rate of Nf(CRNf)=59.9%], followed by SBSMA (CRNf=46.1%) and HVMA (CRNf=26.2%). However, the effect of long-term aging on the fatigue properties of HVMA (CRNf=99.2%) is the largest, followed by that of CRMA (CRNf=95.8%) and SBSMA (CRNf=56.6%). At low temperature, compared with CRMA and HVMA, aging had the greatest influence on the low-temperature rheological properties of SBSMA. In addition, the three finished product–modified asphalt binders exhibited similar changes in microscopic level after aging.

Repair of Bulk-Fill and Nanohybrid Resin Composites: Effect of Surface Conditioning, Adhesive Promoters, and Long-Term Aging.

The aim of the study was to investigate the effect of different repair procedures on the repair bond strength of bulk-fill and nanohybrid resin composites after different aging periods. The resin composite blocks (8 × 8 × 4 mm3) were prepared from a bulk-fill (reliaFIL Bulk) and a nanohybrid (reliaFIL LC) resin composite and grouped according to aging duration (6 months, 1 year, and 2 years). Following aging, the blocks were assigned to different surface treatments; air-abrasion with aluminum oxide powder, roughening with a diamond bur, and no treatment. After cleansing with phosphoric acid, a silane layer (Porcelain Primer) was applied on the surface of half of the specimens in each group. The specimens were subdivided into two groups (n = 5): Scotchbond Universal (3M Oral Care) and All-Bond Universal (Bisco). The blocks were repaired with the nanohybrid composite (8 × 8 × 8 mm 3). The repaired specimens were stored in distilled water (37 °C/24 h) and segmented into beams. Half of the beams were immediately subjected to microtensile μTBS testing (1 mm/min), while the other half was stored in distilled water (37 °C) for 6 months before testing. Failure modes were analyzed using stereomicroscope and SEM. Statistical analyses were performed with ANOVA and least significant difference tests (LSD) tests (p = 0.05). The extension of aging periods (6 months, 1 year, and 2 years) reduced the repair bond strength in some groups for both resin composites (p < 0.05). The air-abrasion and bur roughening improved the repair bond strength (p < 0.05). The silane application did not influence the repair bond strength and durability (p > 0.05). There was no difference among the universal adhesives in the same surface treatment groups (p > 0.05). The mechanical roughening treatments are necessary for the repair of resin composite. The universal adhesives might be used for the repair of resin composites regardless of silane content without prior silane application.

Effect of long-term natural aging on the tensile and fracture properties of aluminum alloy AA2219-T87 parent and weldments at room and cryogenic temperatures

Aluminum alloy (AA2219) is widely used for the fabrication of earth storable and cryogenic propellant tanks. To ensure flight safety, it is important to understand the effect of long-term storage on the mechanical properties, which are dependent on the microstructure. Therefore, the present work is carried out to understand the effect of long term (11 years) ambient storage on the tensile and fracture properties of AA2219-T87 in parent material and weld joint. The tensile test results of naturally aged AA2219-T87 material for 11 years in both parent and weldments indicate an increase in tensile strength at room and cryogenic (77 and 20 K) temperatures. STEM-HAADF and TEM analysis revealed the presence of well-oriented densely populated CuAl2 precipitates (plate-like θ’ and θ” precipitates). The changes in mechanical and fracture properties were understood from the quantification of precipitate distribution, that can be attributed to the natural aging phenomenon taking place at ambient conditions, during the extended period of storage. Here, we report the mechanism towards understanding the increase in strength of AA2219-T87, by the growth of the finer θ” precipitates during natural aging. Since tensile (RT, 77 K, and 20 K) and fracture properties (RT) of welds have improved, with no significant reduction in ductility, long-term naturally aged (up to 11 years) fabricated products of AA2219-T87 are flightworthy.

Effect of short-term and long-term ageing on the elastic and creep behaviour of modified binder containing different SBS copolymer

Effect of short-term and long-term ageing on the elastic and creep behaviour of modified binder containing different SBS copolymer