Indirect Tensile Fatigue Test Research Articles

Mesoscopic Analysis of Fatigue Damage Development in Asphalt Mixture Based on Modified Burgers Contact Algorithm in Discrete Element Modeling.

This study is aimed at examining the mesoscopic mechanical response and crack development characteristics of asphalt mixtures using the three-dimensional discrete element approach via particle flow code (PFC). The material is considered an assembly of three phases of aggregate, mortar, and voids, for which three types of contact are identified and described using a modified Burgers model allowing for bond failure and crack formation at contact. The laboratory splitting test is conducted to determine the contact parameters and to provide the basis for selecting three different load levels used in the indirect tensile fatigue test and simulation. The reliability of the simulation is verified by comparing the fatigue lives and dissipated energies against those from the test. Under cyclic loading, the internal tensile and compressive force chains vary dynamically as a response to the cyclic loading; both are initially concentrated beneath the top loading strip and then extend downward along the loading line. The compressive chains are oriented roughly vertically and develop an elliptic shape as damage grows, while the tensile chains are mostly horizontal and become denser. An analysis based on the histories of the numbers of different contact types indicates that damage mainly originates from bond failures among the aggregate particles and at the aggregate-mortar interfaces. In terms of location, cracking is initiated below the loading point (consistent with observations from the force chains) and propagates downward and laterally, leading to the macrocrack along the vertical diameter. The findings provide a mesoscopic understanding of the fatigue damage initiation and propagation in asphalt mixture.

Waste cooking oil based capsules for sustainable self-healing asphalt pavement: Encapsulation, characterization and fatigue-healing performance

Waste cooking oil has surfaced as a hazardous waste that induces severe environmental contamination. Encapsulation technology presents a viable solution to regenerate the waste oil and augment the self-healing ability of asphalt materials. This study characterized capsules synthesized with selected waste oil for self-healing asphalt mixture, and evaluated the self-healing and environmental impact. The wetting ability, capillary, anti-aging, and self-healing performance of three potential healing agents were analyzed, and the optimal healing agent was obtained by evaluating the comprehensive behavior with the radar chart method. Capsules were synthesized using the ionic gelation method, and their thermal stability, chemical structure, mechanical performance, and morphology were characterized. Fatigue-healing performance asphalt mixture with capsules were investigated by indirect tensile fatigue test with intermittent time. Leakage of waste oil core were measure to verify it environmental impact to surroundings. Results showed that all healing agents could restore the aged asphalt, and waste rapeseed oil had superior overall performance with comprehensive fi value of 0.993 in radar chart evaluation. The compression characteristic of the capsules could transform from brittleness to plasticity as the water-to-oil(WO) ratio decreases from 15 to 5. SEM observation implied when the WO ratio varied from 10 to 15, the multi-pore structure of capsules could be appropriately filled. The addition of capsules in the mixture increased the fatigue life extension rate (HDf) of aged mixtures (with intermittent time 0.1 s∼0.8 s) by 10∼30%. Leakage of waste oil from the mixture was inhibited, substantially reducing 38% release of waste oil. This can serve as a means for the sustainable utilization of waste oil, thereby mitigating environmental pollution and negative effects caused by waste oil.

Distinctive mechanism and model for whole-life ratcheting of cement-stabilized aggregates in tensile fatigue tests

In light of the limited research on the fatigue damage and plastic strain evolution of cement-stabilized aggregates (CSA) despite their widespread application, this study aims at modeling the ratcheting of CSA, which provides better characterization of fatigue by counting plastic strain accumulation. Uniaxial and indirect tensile fatigue tests were conducted to obtain the plastic strain accumulation and stress-strain curves. A bar system was constructed to describe the ratcheting mechanism of CSA, which considers the non-homogeneity of CSA's components and composes parallel bars with a distribution of plastic-damage properties. The ratcheting rate variation was attributed to the strength distribution of the bars. Then, to prevent complex and hard-to-implement parameter fitting, a predigested ratcheting model was proposed, which focuses only on the secant modulus and simplifies the generation of ratcheting to the difference between reloading and unloading secant modulus. The test results revealed a three-stages characteristic in the ratcheting evolution of CSA. The non-coincidence of reloading and unloading curves was deemed the intuitive cause of the ratcheting. The numerical implementation of the proposed mechanism indicated that the strength and modulus discrepancies between weak and strong bars can lead to ratcheting. By comparing with the experimental results, the effectiveness of the proposed model was verified in describing the ratcheting evolution of CSA and to characterizing the non-linearity of the accumulation curves. Moreover, the parameter fitting process requires the results of the current fatigue test instead of parallel tests or other loading tests, successfully eliminating calibration difficulties resulted from significant property discrepancies among CSA specimens.

Evaluation of Asphalt Binder and Mixture Properties Utilizing Fish Scale Powder as a Biomodifier

Fish represent an abundant and underutilized waste product from the fishing industry. This study investigated the effects of incorporating fish scale powder (FSP) at various dosages (3%, 6%, 9%, and 12%) on the properties of asphalt binder and mixtures. Conventional tests, viscosity, storage stability, Fourier transform infrared spectroscopy, and multiple stress creep recovery tests were conducted on the binder. Mix design, wheel tracking, indirect tensile strength, fatigue, and ultrasonic pulse velocity tests were evaluated for the asphalt mixtures. The results showed that FSP increased binder stiffness and reduced temperature susceptibility but compromised low-temperature performance and workability regardless of dose. The storage stability test results showed improved high-temperature storage stability. In the mixtures, the permanent deformation resistance increased with increasing FSP content, decreasing the rut depth from 4.3mm for the control to 2.9mm at 12% FSP. The moisture damage resistance, indicated by the tensile strength ratio, increased from 90% for the control to 94.1% at 12% FSP. However, the fatigue life decreased from 14,010 cycles for the control sample to 11,190 cycles at 12% FSP. The dynamic and elastic modulus values before conditioning increased with higher FSP dosages, and this increasing trend was also observed after conditioning, signifying greater stiffness retention and moisture resistance of the asphalt mixtures containing higher amounts of FSP. Numerically, the 6-9% FSP range offered the optimum balance, enhancing the rutting resistance by 18% and moisture resistance by 3.2% compared to those of the control, while limiting the fatigue life to 12% and maintaining the workability. Overall, fish scale powder has potential for use as an asphalt biomodifier by transforming an environmental liability into a value-added sustainable paving material.

Using surface free energy and mechanical methods to investigate the effect of aging on the fatigue cracking potential of UHMWPE-modified HMA

Aging due to environmental conditions significantly affects the occurrence of fatigue cracking in hot-mix asphalt (HMA). Previous analyses showed that aging reduces mastic resistance and bitumen-aggregate adhesion, but these experiments were usually performed on HMA samples, and failure mechanisms were not reflected in the results. Accordingly, via the surface free energy (SFE) theory, this study examined the impact of aging on the fatigue cracking mechanism of HMA. Dynamic methods, including indirect tensile fatigue test (ITFT) and Pull-Off tensile strength (POTS), were applied to HMA samples at 5 and 20 ˚C to study the association between the results of SFE tests. Two performance-graded bitumens (PG 58–22 and PG 64–16), two aggregates with different mineralogical properties (limestone and siliceous), and a polymeric additive (ultra-high-molecular-weight polyethylene-UHMWPE) as a bitumen modifier were also used. Based on the results, aging decreased and increased the polar (28.6%) and non-polar (15.14%) properties of bitumens, respectively. A decline in polar properties lowered the bitumen-aggregate adhesion (8.11%), which was generally because of polar bonds. The rise in cohesion free energy (CFE) by up to 9.5% and non-polar properties due to aging decreased the failure probability in the bitumen film of the aged specimens. UHMWPE improved the non-polar properties of the asphalt (by up to 15.09%), providing greater resistance against aging and reduced adhesion with mineral aggregates. According to the POTS test results at the state of cohesive failure, aging enhanced the POTS of cohesion, especially in UHMWPE-modified bitumen-aggregate by up to 12.12%. POTS in the state of cohesive failure was independent of adhesion free energy (AFE), yet CFE influenced POTS at the state of adhesive failure. Based on the fatigue life of HMA, even though aging increased the CFE and stiffness of HMA, the decline in the AFE parameters and flexibility reduced the fatigue life of the aged HMA in comparison to similar non-aged specimens (by up to 5.17%). The polymer additive significantly improved the resistance of asphalt mixtures to cohesion (by up to 23.16%), adhesion (by up to 16.78%), and fatigue life (by up to 12.8%). Additionally, in aged samples, there was a noticeable reduction in the parameters of cohesion, adhesion, and fatigue life in the modified samples compared to the base samples.

Carbon Sequestration via Bituminous Composites Containing Recycled High-Density Polyethylene

This paper presents an innovative bituminous composite containing recycled high-density polyethylene (HDPE) as a means of carbon sequestration. To prepare the composite, rejuvenators and recycled HDPE were introduced to reclaimed asphalt pavement (RAP), separately and in combination. To evaluate efficacy of rejuvenators, this study used the following three rejuvenators: waste engine oil (WEO), oleic acid (OA), and vacuum bottom (VB). The performance of the bituminous composite containing HDPE and rejuvenators was evaluated using the indirect tensile fatigue test, the rutting resistance test, the resilient modulus test, and the semi-circular bending test. Results showed that applying a combination of rejuvenators and recycled HDPE improved the resistance to fatigue, rutting, and cracking. Particularly, in terms of improving resistance to cracking, OA proved to be the most effective rejuvenator, followed by WEO and VB. In all bituminous composites studied here, the hybrid application of HDPE and rejuvenator proved to be more effective than the rejuvenator or HDPE alone.

Performance investigation of phenol–formaldehyde resin (PF) and organic montmorillonite (OMMT) compound-modified bituminous mixture

ABSTRACT Composite modification has proven to be an effective strategy in addressing the insufficient performance associated with single-modified bituminous mixture. This research aims to thoroughly investigate the performance of the compound-modified bituminous mixture incorporation phenol–formaldehyde resin (PF) and organic montmorillonite (OMMT). The performance investigations of the bituminous mixture were conducted through the Marshall stability test, dynamic stability test, indirect tensile test, immersion Marshall test, freeze–thaw splitting test, indirect tensile fatigue test and long-term aging test. The test results indicated that OMMT plays a crucial role in advancing thermal storage stability and compatibility between PF and bitumen. Importantly, the optimal dosage of OMMT was determined not to exceed 5%. The 3%PF+5%OMMT bituminous mixture demonstrated excellent rutting and cracking resistance, superior water stability and anti-fatigue capabilities. Furthermore, the 2%PF+5%OMMT and 3%PF+5%OMMT bituminous mixtures exhibited superior anti-aging abilities. In consideration of laboratory performance and bitumen compatibility, the combination of 3%PF+5%OMMT can be utilised to enhance the bituminous mixture performance. The results of single-factor analysis of variance indicated that PF and OMMT had significantly impact on the bituminous mixture performance. Notably, the influence of PF/OMMT dosage on the cracking resistance, water stability and anti-aging ability requiring attention when considering them as bitumen modifiers.

Enhancing HMA properties with polypropylene-based face mask integration: A qualitative comparison of wet mixing and dry mixing techniques

<span lang="EN-US">In the wake of the emergence and widespread dissemination of the COVID-19 coronavirus, scientifically identified as SARSCoV-2, the utilization of medical equipment, specifically tri-layered polypropylene (PP)-based face masks, has experienced significant proliferation. The extensive adoption of single-use polymer-based face masks has raised notable environmental concerns, given their extended degradation period of up to 480 years and their substantial threat to ecosystems, particularly aquatic organisms, due to pervasive littering practices. Hence, this study is dedicated to assessing the influence of incorporating polypropylene (PP)-based face masks into asphalt formulations. The incorporation of PP-based face masks into asphalt was executed at three distinct weight percentages, employing both dry and wet mixing techniques. Comprehensive performance evaluations were carried out utilizing the Marshall test, indirect tensile fatigue test, and Hamburg wheel tracking rutting experiments and the best value for each. Remarkably, augmenting the PP content yielded improvements in both fatigue life and rutting resistance of the asphalt mixtures, and the maximum improvement was recorded at 0.3% replacement. Notably, asphalt specimens prepared using dry mixing techniques outperformed their wet mixing counterparts, demonstrating superior cohesion attributes.</span>

Evaluation of asphalt concrete’s fatigue behavior using cyclic semi-circular bending test

Fatigue cracking in asphalt concrete (AC) is one of the major distresses that cause premature failure of flexible pavements. Fatigue tests are often lengthy, cumbersome, and expensive. Therefore, in the performance-related mix-design specifications, some static tests are recommended due to their simplicity. The monotonic semi-circular bending (SCB) test is among the most popular. Even though the SCB test is practical, the actual number of cycles to failure due to cyclic loads cannot be obtained. Implementing SCB testing under cyclic loading conditions for AC performance evaluation could be promising. This study aims to develop a cyclic SCB fatigue testing method. To this end, SCB specimens were produced, and static SCB fracture testing was first conducted to determine the loading levels of the cyclic SCB fatigue test. Then, cyclic SCB tests were conducted by varying load levels to obtain the S-N (stress-fatigue life) curves. To demonstrate the applicability of the proposed framework to differentiate fatigue behavior of mixtures, two AC mixtures were designed and subjected to the proposed protocol, varying the type of aggregate (gneiss and mica schist). Additionally, the S-N curves from cyclic SCB tests were compared to the ones from indirect tensile (IDT) fatigue tests. A considerable similarity in the results between the two approaches (SCB vs. IDT) under cyclic loading was observed, while SCB showed good test repeatability. The SCB configuration with a pre-notch allows fracture mechanics-based testing to monitor the cracking mechanisms and promote rapid cracking evolution, which can reduce testing time.

Summarizing the Effect of Mixture Variables and Test Parameters on Fatigue Performance of Asphalt Mixtures

Abstract Fatigue cracking performance of asphalt mixtures is significantly affected by mixture variables and environmental and loading conditions in the field. Thus, there is a need to understand the effect of critical factors on the fatigue cracking resistance of asphalt mixtures through an extensive study. For this purpose, the present research is focused on characterizing fatigue cracking resistance of asphalt mixtures by considering different factors such as aggregate gradations (two dense and two gap gradations), binder types (two unmodified and three modified binder types), binder content (optimum binder content and optimum binder content ±0.5 %), test temperatures (15°C, 25°C, and 35°C), and three stress levels for different asphalt layer thicknesses (40, 80, 120, 160, 200, and 240 mm). An indirect tensile fatigue test was performed to characterize fatigue cracking resistance of asphalt mixtures, and a Kaplan–Meier survival analysis was carried out to examine whether the factors that were considered significantly affected the fatigue performance. Pavement sections with varying thicknesses of asphalt layers were analyzed using IITPAVE, a pavement analysis software, to compare the mixtures’ fatigue performance. All of the variables taken into consideration in this study were shown to have a statistically significant effect (p value < 0.05). However, the binder type had a stronger influence than the other variables on the resistance to fatigue cracking. Finally, a fatigue life equation (adjusted R2 = 0.77) was developed considering all the mixture combinations, which can be used for determining the laboratory fatigue life of asphalt mixtures.

Performance of coconut fiber as bitumen modifier in asphalt mixture influence to fatigue resistance

One of the most prevalent challenges faced in road construction is pavement distresses produced by ageing asphalt pavement, which resulted in fatigue cracking. Fatigue cracking is regarded as one of the primary failure types when the tension in the bituminous layer is low due to high vehicle traffic load repetition. The study focuses on evaluating the performance of coconut fiber as modifier in bitumen penetration grade 60/70. The addition of 0.5%, 0.75% and 1% were used in this study to determine the effect on asphalt mixture. Indirect tensile fatigue test were conducted to determine the life cycle of the sample. The result showed that the increasing percentage of coconut fiber will improve the bitumen physical properties and increased the life cycle of asphalt mixture. In this study, 1% coconut fiber produced the best result. In conclusion, the addition of coconut fiber into bitumen can improve the performance of asphalt mixture in term of fatigue resistance.

Fatigue damage investigation on asphalt concrete under cyclic freeze–thaw using a combined energy and viscoelasticity method

The fatigue damage of asphalt concrete (AC) concerns pavement design and maintenance in cold regions with multiple freeze–thaw (F-T) cycles. Previous studies contribute significantly to investigating the adverse effect of repeated F-T cycles on fatigue damage of AC using phenomenological and dissipated energy (DE) methods. However, few have related the damages to the viscoelastic property of AC. Thus, this research aims to introduce a combined method of DE and viscoelasticity to investigate the fatigue damage evolution in AC under F-T cycles. Using the indirect tensile fatigue test (ITFT), the fatigue life evolution with the increasing F-T cycles was investigated through the measured energy ratio (ER) and accumulated permanent strain (APS). Additionally, a viscoelastic model was introduced to describe the APS under different F-T cycles. The goodness-of-fit represented by R2 of all models was greater than 0.85. Also, the correlation result shows a close relationship between fatigue lives predicted by ER and APS, with an R reaching 0.96. Hence, the combination of DE- and APS-related methods provided a comprehensive prediction of fatigue damages of AC subjected to repeated F-T cycles. This study revealed the evolution of AC fatigue damage under the F-T cycles, which can help narrow the gap between the designed and actual lives of asphalt pavements serving in the cold region.

Fracture studies on basalt fiber reinforced asphalt mixtures with reclaimed asphalt pavement derived aggregates and warm mix additives

The Indian Ministry of Road Transport and Highways’ (MoRT&H) recommended grade II Bituminous Concrete mixture, hitherto referred to as Asphalt Concrete (AC) was investigated during this present research study. Different AC mixtures, with 2 % to 4 % of Sasobit warm mix additive by weight of the asphalt binder, 20 % to 40 % of RAP derived aggregates as replacement to the virgin aggregates and 4 % to 8 % of basalt fibres by weight of the binder as the additive, were investigated during this research study.In addition to the fundamental binder tests, micro structural investigations namely X-Ray Diffraction (XRD) and Fourier-Transform Infrared spectroscopy (FT-IR) were also carried out to understand the crystallographic structure and the functional groups present in the binder, respectively. The efficacy of the WMA and basalt fibre addition in the AC mixtures with RAP derived aggregates was verified through the standard Immersion Type-Hamburg Wheel Track Test (IHWTT) for assessing the rut resistance; through the standard Semi-Circular Bending (SCB) tests for assessing fracture behaviour, and through indirect tensile fatigue test to assess fatigue resistance. It was observed that the AC mixture, with 30 % RAP materials by weight percentage of total aggregates, 6 % chopped basalt fibres by weight percentage of binder and 4 % Sasobit warm mix additive dosage by weight percentage of binder, was found meeting the target AC mixture performance standards.

Mechanical Properties of Open-Graded Asphalt Friction Course Mixtures with Basic Oxygen Furnace Steel Slag as Coarse Aggregates

Open-graded asphalt friction course (OGAFC) is an asphalt course constructed over a dense-graded and impermeable surface to allow quick drainage of surface water runoff and enable reduction of hydroplaning and splash and spray. OGAFC mixtures demand high-quality aggregates to perform the intended functions while transferring traffic loads to the underlying layer. Steel slag is a byproduct generated during steel production, and large quantities are unutilized in steel-producing countries, including India. This study evaluated the mechanical performance properties of OGAFC mixtures using basic oxygen furnace (BOF) steel slag as replacement for coarse aggregates at percentages of 0%, 25%, 50%, 75%, and 100%. OGAFC mixtures with two types of modified asphalt binders and five percentage replacements of coarse natural aggregates with BOF steel slag were fabricated. The mechanical performance of the OGAFC mixtures was evaluated in terms of rutting resistance (dynamic creep test and Hamburg wheel tracking device test), cracking potential (indirect tensile strength, cracking tolerance index, and semicircular bending test), fatigue life (indirect tensile fatigue test), and modulus properties (indirect tensile stiffness modulus and resilient modulus). The test results indicated that the use of BOF steel slag not only improved the performance of OGAFC mixtures in terms of rutting resistance, cracking potential, and modulus properties, but also increased the fatigue life of the OGAFC mixes. OGAFC mixes up to 100% BOF steel slag content exhibited superior performance compared with the mixtures with natural aggregates.

Performance Evaluation of Hot Mix Asphalt (HMA) Containing Polyethylene Terephthalate (PET) Using Wet and Dry Mixing Techniques

This study evaluates the performance of Polyethylene Terephthalate (PET)-modified hot mix asphalt. Aggregate, bitumen of grade 60/70 and crushed plastic bottle waste were utilized in this study. Polymer Modified Bitumen (PMB) was prepared using a high shear laboratory type mixer rotating at a speed of 1100 rpm with varying PET content of 2%, 4%, 6%, 8% and 10%, respectively. Overall, the results of preliminary tests suggested that bitumen hardened with the addition of PET. Following optimum bitumen content determination, various modified and controlled HMA samples were prepared as per wet and dry mixing techniques. This research presents an innovative technique to compare the performance of HMA prepared via dry and wet mixing techniques. Performance evaluation tests, which include the Moisture Susceptibility Test (ALDOT-361-88), Indirect Tensile Fatigue Test (ITFT-EN12697-24) and Marshall Stability and Flow Tests (AASHTO T245-90), were conducted on controlled and modified HMA samples. The dry mixing technique yielded better results in terms of resistance against fatigue cracking, stability and flow; however, the wet mixing technique yielded better results in terms of resistance against moisture damage. The addition of PET at more than 4% resulted in a decreased trend for fatigue, stability and flow due to the stiffer nature of PET. However, for the moisture susceptibility test optimum PET content was noted to be 6%. Polyethylene Terephthalate-modified HMA is found to be the economical solution for high volume road construction and maintenance, besides having other significant advantages such as increased sustainability and waste reduction.

Research on failure strength master curve and fatigue performance of asphalt mixture containing high-proportion reclaimed asphalt pavement

Reclaimed Asphalt Pavement (RAP) is a cleaner production widely used in road engineering. In order to investigate the failure strength and long-term performance of high-proportion RAP asphalt mixture, this research prepared two high-content RAP recycled asphalt mixtures (50% and 60% RAP-RAM) with the gradation of AC-20 based on Styreneic Methyl Copolymer (SMC) regenerant. Firstly, indirect tensile (IDT) strength tests were implemented on 50% and 60% RAP-RAM at four temperatures and six loading rates. Secondly, IDT fatigue tests at six stress levels were carried out. The relationships of strength and temperature, strength and loading rate were obtained based on strength test results. The master curve model of indirect tensile strength and loading rate of high-proportion RAP recycled asphalt mixture was established by linear and Sigmoidal functions. On the basis of the Sigmoidal strength master curve equation, the fatigue stress ratio was calculated. Finally, this paper established the fatigue equation of the high-content RAP recycled asphalt mixture based on the fatigue stress ratio. The analysis results show that 50% and 60% RAP-RAM based on SMC regenerant show favorable strength and fatigue properties. In addition, increasing the proportion of RAP improves the strength of the mix while reducing the loading rate sensitivity of strength. However, the fatigue performance of the mix reduces by increasing RAP content. The fatigue equation based on the fatigue stress ratio takes the factors of temperature and loading rate into account, reflecting the mix's fatigue performance more realistically. The strength and fatigue performance results verify the reliability of the high-content RAP recycled asphalt mixture based on SMC regenerant and provide a reference for the effective utilization of RAP which can generate environmental benefits of saving aggregate and asphalt and reducing energy consumption and carbon emissions.

Fatigue performance of graphene oxide modified asphalt mixture: experimental investigation and response surface methodology

Fatigue in asphalt pavements is a major deterioration caused by repeated traffic loading. The objectives of this research were to investigate the fatigue performance of graphene oxide (GO) modified asphalt mixtures and evaluate the influence of temperature and stress level on the fatigue life of GO asphalt mixtures using response surface methodology (RSM). For this purpose, an indirect tensile fatigue test was conducted. The results showed that the application of GO increased the fatigue life of the asphalt mixture. The RSM analysis proposed a quadratic model with a high determination coefficient (R2 = 0.9977) to fit the experimental data. The ANOVA test showed that temperature, stress level, and GO percentage had a pronounced effect on the fatigue performance of the mixture. Furthermore, multi-objective optimization was used to achieve an optimized mixture proportion and verify the model’s reliability by conducting validation experiments. The predicted and actual results were found to be in excellent agreement, with a variation of only 2.12%, suggesting that the model can accurately predict the fatigue life of the GO-modified asphalt mixture.

Stiffness, rutting, and fatigue performance evaluation of cement-natural rubber latex stabilized recycled concrete aggregate

ABSTRACT The stiffness, rutting, and fatigue performance of cement-natural rubber latex (NRL) stabilized recycled concrete aggregate (RCA) were evaluated under cyclic loading. The RCA was stabilized with 3% cement content and dry rubber content to cement (r/c) ratios at 5%, 10% and 15%. The performance evaluation was carried out through advanced experiments, including indirect tensile resilient modulus test, indirect tensile fatigue test, and rutting susceptibility test using a Hamburg wheel tracking device. The results indicated that the r/c ratio of 10% was optimum for cement-NRL stabilized RCA (3C10R-RCA), which exhibited the optimum performance in terms of permanent deformation, fatigue cracking, and rutting susceptibility. The indirect tensile fatigue life of 3C10R-RCA was found to be 79.3% greater than that of the 3% cement stabilized RCA (3C-RCA), while the rut depth of 3C10R-RCA was 8% lower. Although the resilient modulus value of 3C10R-RCA was slightly lower than that of 3C-RCA, the tensile permanent deformation was found to be lower, which is associated with the lower rut depth. As a result of the significant improvement in fatigue life and rutting performance, the resistance to fatigue cracking and premature failure of cement-NRL stabilized RCA were improved.

Effect of Nano-Cobalt Oxide on the Rheological Behavior of Asphalt Binder and Mechanical Characteristics of Hot Mix Asphalt

In this study, the effects of nano-cobalt oxide (nano-CoO) (1 and 2% by asphalt binder weight) on the rheological behavior of the asphalt binder and mechanical characteristics of asphalt mixtures were examined. To evaluate the behavior of the asphalt binder at moderate and high temperatures, the dynamic shear rheometer (DSR) test was used. Besides, to study asphalt mixtures’ rutting potential and fatigue cracking, the repeated load axial (RLA) test and the indirect tensile fatigue test (ITFT) were conducted, respectively. Based on the rheological tests, adding 1 and 2% of nano-CoO to asphalt binder increases the complex modulus (G∗) and reduces the phase angle (δ) at high temperatures and significantly improves the modified asphalt binder’s rutting parameter. Also, at moderate temperatures, the addition of nano-CoO reduced the fatigue parameter of the modified asphalt binder compared to the control asphalt binder. It was demonstrated that the permanent strain of the modified specimens was decreased by about 35% compared to that of the control specimens. The fatigue tests at two temperatures and five stress levels also showed that incorporating nano-CoO significantly increased (about 90%) the fatigue life of modified samples compared to controlled samples.

Study on the high and low temperature performance of nano alumina modified asphalt mixture

To improve the high and low temperature performance of asphalt mixture, nano alumina was used as additive in this study. Firstly, the high temperature characteristics of asphalt mixture with different content of nano alumina were studied by rutting test and dynamic creep test. Secondly, the fatigue properties of modified asphalt mixture at different temperature were tested by indirect tensile fatigue test. Finally, the low temperature bending test and indirect tensile test were used to evaluate the low temperature performance. The results show that nano alumina can improve the high temperature and fatigue properties of asphalt mixture to some extent, while the low temperature performance decreases slightly.