Indirect Tensile Test Research Articles

Assessment of the Production Variability and Composite Performance Index for Conventional and High Reclaimed Asphalt Pavement Balanced Mix Design Mixtures

The balanced mix design (BMD) concept enables the design of engineered mixtures containing conventional and high reclaimed asphalt pavement (HRAP) contents, moving beyond the constraints of traditional volumetric design methodologies. During production, the designed mixture undergoes verification and potential modifications at the plant to accommodate actual production and field circumstances, regardless of the mix design method. This study assessed the impact of production and associated performance variability on a volumetrically designed control mixture and five mixtures designed with the BMD concept. This investigation showed relatively precise gradation control, but exceedances of volumetric property tolerances were observed in BMD-optimized mixtures during production. Performance, including durability, cracking, and rutting susceptibility, was evaluated using the Cantabro test, indirect tensile cracking test (IDT-CT), and asphalt pavement analyzer (APA) test, respectively. Test results uncovered that produced mixtures may become unbalanced. Observations from the Cantabro test and IDT-CT highlighted the necessity and effectiveness of employing the BMD for HRAP mixtures. The potential aging effect introduced during the reheating process may compromise durability and cracking resistance. In addition, a three-dimensional plot with a revised composite performance index (CPIR) was used to optimize the process of evaluating the mixture “balance” status among multiple primary performances. It revealed that almost all produced HRAP mixtures demonstrated a well-balanced status. Finally, agencies can use the CPIR as part of their acceptance program for BMD mixtures to determine a pay factor for possible bonuses or penalties.

Effect of Chemical Composition on Rheological Properties of Asphalt Binders Modified with Rap Binders and Rejuvenator

Conventional rejuvenating agents such as virgin binders, polymers and so on, poses environmental, technical, and economic challenges. The objective of this study is to investigate the interaction between chemical components and rheological behavior of hot mix asphalt modified with RAP binder and diesel engine waste oil (DEWO) as rejuvenator. 7.2% DEWO was added to the RAP binder to achieve the modified binder (MB), and the effects of the rejuvenator through the MB were evaluated at varying percentages (0 to 100% by weight of the virgin binder) using Dynamic Shear Rheometer (DSR) under short and long-term aging at high and intermediate temperatures, as well as low temperatures using Bending Beam Rheometer (BBR). Saturates, aromatics, resins, and asphaltenes (SARA)-separation, Indirect tensile stiffness modulus test (ITSM), and fatigue life test were also employed to investigate the interaction between chemical components and rheological properties of binder. Results indicated that incorporating 50% modified RAP binder significantly enhanced the performance of the asphalt mixtures, it was also discovered that 100% of RAP content meets standard specifications when modified with oil rejuvenators. This research suggests that large quantities of diesel engine waste oil can be diverted from landfills and employed as useful resource in asphalt production.

Lime Stabilization of Tropical Soil for Resilient Pavements: Mechanical, Microscopic, and Mineralogical Characteristics.

Lime stabilization is a sustainable technique due to its use of local materials, increased durability, reduced maintenance, and improved resistance to water action. This paper examines the impact of lime stabilization on the mechanical, microscopic, and mineralogical properties of a tropical soil. Two types of lime, calcitic and dolomitic, were tested at 3% and 5% by weight. Compressive, indirect tensile and flexural test results and statistical analysis revealed that calcitic lime mixtures had higher strength and stiffness, whereas dolomitic lime mixtures exhibited greater deformability with higher tensile strain at break. Scanning electron microscopy indicated that the soil's porous matrix closed within 7 days for both lime types due to flocculation, with increased matrix interlocking over time. The calcitic lime mixture developed a more closed matrix compared to the dolomitic lime, which showed weaker cementing. X-ray diffraction analysis indicated higher consumption of clay minerals and a notable reduction in calcium hydroxide peaks in the lime-treated soils. The study concludes that calcitic lime provides better pavement performance for stabilizing the soil, enhancing its engineering properties while also being sustainable by reducing the need for raw material extraction and improving resilience to climate-related issues such as floods.

Using the indirect tensile fatigue test to evaluate fatigue characterisation of asphalt mixtures

Fatigue cracking is a principal structural failure mode in asphalt pavement layers, resulting from repeatedtraffic-induced loading stresses. Therefore, understanding fatigue deterioration behaviour is crucial for ensuring effective pavement design. In recent years, the indirect tensile fatigue test has become one of the mostcommonly used methods for evaluating the fatigue behaviour of asphalt mixtures, owing to its simplicity andsuitability for cylindrical specimens either produced in the laboratory or cored from pavement constructionsites. In this research paper, the indirect tensile fatigue test was employed to assess the stiffness modulus andfatigue behaviour of one unmodified asphalt mixture (DBM50) and two polymer-modified mixtures (EME2and SMA) in stress-controlled mode across various temperatures. The results indicated that the indirect tensile fatigue test worked well and it can be considered to characterise effectively fatigue behaviour of differentasphalt mixtures in Vietnam. In addition, the test results revealed that the SMA mixtures exhibited the bestperformance at both 20 °C and 10 °C compared to other mixtures. Specially, the fatigue lines for DBM50 andSMA at 20 °C were positioned above those at 10 °C, while the fatigue lines for EME2 lines remained quitesimilar across both temperature levels.

Performance of Asphalt Mixtures Modified with Desulfurized Rubber and Rock Asphalt Composites

This study explores the performance of asphalt mixtures modified with North American rock asphalt and desulfurized rubber particles at varying rubber-to-asphalt ratios ranging from 18% to 36% by weight. A comprehensive set of laboratory tests, including high-temperature rutting tests, low-temperature bending tests, indirect tensile tests, and freeze–thaw splitting tests, were conducted to evaluate the modified mixtures. The results indicate that both wet and dry blending methods produce mixtures that meet technical requirements, with the optimal asphalt-to-aggregate ratio determined to be 7.1%. At a rubber-to-asphalt ratio of 18%, the wet blending method slightly improves high-temperature rutting resistance compared to the dry method. However, an increase in rubber content generally enhances rutting resistance regardless of the blending technique. The wet blending method excels in low-temperature crack resistance, possibly due to better rubber dispersion, while an increase in rubber content diminishes crack resistance due to a thinning asphalt film. In terms of fatigue performance, the dry blending method results in significantly longer fatigue life, with a 27% rubber-to-asphalt ratio exhibiting optimal balance. The dry method consistently outperforms the wet method in water stability, and the resistance to water damage increases with rubber content. In conclusion, this study provides valuable insights into optimizing rubber-to-asphalt ratios and blending methods for various application needs, showcasing the benefits of rock asphalt and desulfurized rubber particles in asphalt modification.

Advancing the performance characteristics of rubber asphalt mixtures through the integration of Basic Oxygen Furnace (BOF) slag: A focus on static and dynamic mechanical enhancements.

To investigate the advantageous effects of incorporating industrial solid waste basic oxygen furnace (BOF) slag on the mechanical characteristics of warm-mixed rubber asphalt (WMRA) and hot-mixed rubber asphalt (HMRA) mixture, varying proportions of BOF slag were substituted for limestone coarse aggregates (0%, 25%, 50%, and 75%). Additionally, a 1.5% dosage of Sasobit warm-mixed modifier was introduced to prepare the rubber asphalt. Subsequent to preparation, both static mechanical tests (including Marshall and indirect tensile tests) and dynamic mechanical tests (including dynamic creep and elastic modulus tests) were conducted to evaluate the influence of BOF slag on the mechanical behavior of WMRA and HMRA mixtures across different substitution levels. Following testing, a two-way analysis of variance (ANOVA) was employed to dissect the impact of BOF slag content and Sasobit warm-mixed modifier on the static and dynamic mechanical properties of the rubber asphalt mixtures. The findings reveal that BOF slag exhibits commendable engineering aggregate properties, enabling substantial substitution of coarse aggregates in both HMRA and WMRA mixtures. As the proportion of BOF slag increases, it enhances the resistance of asphalt mixtures to permanent deformation and cracking under static and dynamic loading conditions, while broadening the range of elastic deformation for both WMRA and HMRA mixtures subjected to repeated loading. Moreover, a synergistic enhancement in the resistance of rubber asphalt mixtures to dynamic load-induced deformation is observed when employing both BOF slag and Sasobit warm-mixed modifier. The findings offer valuable insights for enhancing the performance of WMRA and HMRA mixtures, as well as broadening the utilization of BOF slag and waste rubber.

Micro- and macro-scale fracture behaviour of brittle rocks: Comparison between the conventional Brazilian test and the advanced universal snap-back indirect tensile test (AUSBIT)

Post-peak behaviour is crucial for the estimation of rock mass fracturing in cave mining operations where hard rocks can exhibit class-II or snap-back response when subjected to loading. Despite the rapid development of research into class-II rocks under compression, the corresponding behaviour in tensile tests has rarely been investigated, which is critical considering the complexity of rock mass fracturing under various stress states. The post-peak response of brittle rocks involves abrupt micro-fracturing, leading to brittle macro-scale behaviour. Controlling the fracture process using the Advanced Universal Snap-Back Indirect Tensile test (AUSBIT) allowed the acquisition of the complete macro-scale class-II behaviour in the post-peak regime, facilitating the use of advanced techniques for insights into both micro and macro-scale fracture. In this study, the AUSBIT tests with digital image correlation (DIC) and acoustic emission (AE) instrumentation were conducted to analyse the progressive failure in Calca granite and Gosford sandstone specimens. Post-test observations of the fracture surfaces were performed using a scanning electron microscope (SEM). From a macroscale viewpoint, the lateral strain control in AUSBIT enabled controlled cracking with significant lateral strain extension prior to failure accompanied by gradual energy dissipation and higher rates of AE activity as smaller magnitudes of energy are being released by each AE hit or microcrack compared to conventional Brazilian tests. The stable microcrack propagation was also identified from SEM observations with more uniform profiles of microcracks and less debris observed in AUSBIT specimens. These findings were more significant in Calca granite, which verified its extreme class-II behaviour while also demonstrating the efficiency of AUSBIT in controlling the violent failure of high-strength brittle rocks commonly encountered in deep mining projects, leading to the acquisition of more accurate material behaviour in terms of micro and macro-scale post-peak features which was unattainable from conventional indirect tensile tests.

Multi-scale damage characterisation of semi-flexible pavements under freeze-thaw cycles

This study aims to investigate the failure mechanism of semi-flexible pavements (SFP) under freeze-thaw conditions and to provide theoretical support for optimizing the material properties. By simulating the freeze-thaw damage process of SFP in actual service scenarios and combining various experimental methods, the strength characteristics and microstructural change rules of SFP in the freeze-thaw process are systematically analyzed. The study used freeze-thaw tests to simulate the real environment, combined with indirect tensile tests (IDT) and three-point bending tests to evaluate the mechanical properties of SFP. To further investigate the failure mechanism, scanning electron microscopy (SEM) was used to observe the interfacial changes between asphalt and early-strength sulphoaluminate cement (JGM301). Additionally, CT scanning was used to capture the structural changes of SFP during freeze-thaw cycles. The results showed that freeze-thaw cycles significantly and negatively affected the split tensile strength of SFP. SEM observations revealed that cracks appeared at the asphalt-cement interface (ITZ), the cement-SBS bond weakened, and the structure of the cement itself became loose. CT revealed structural changes such as cracking at the interface of the two-phase material, creation of new voids, and linkage of old voids during freeze-thawing of the SFP. In summary, the reduction in adhesion at the cement-asphalt interface and the frost swelling of JGM301 are the main reasons for the damage of SFP in freeze-thaw cycles. This study provides an important basis for an in-depth understanding of the freeze-thaw damage mechanism of SFP and optimization of its performance.

Influence of crack configurations of asphalt mortar on the loading response characteristics of cracks under low-temperature conditions

Asphalt mortar is the base material used in asphalt concrete, and its mechanical properties directly affect those of the prepared asphalt concrete. An analysis of the loading response characteristics of cracks in asphalt mortar under low-temperature conditions can help reveal the interaction effect of multiple cracks in asphalt concrete and the influence mechanism of aggregates on the crack propagation and evolution behaviors. In this study, various forms of pre-cracks were generated in asphalt mortar specimens using the water jet cutting technology. Combined with the discrete element method (DEM), an indirect tensile (IDT) test and a virtual IDT test were conducted to analyze the effects of the crack deflection angle (β) and crack length (r) on the crack propagation behavior from macro- and meso-perspectives. The main results showed that: (1) Changes in the crack shape parameters (β and r) not only induced multiple branch cracks in the asphalt mortar but also led to the development of II Mode fractures; (2) With the increase in the crack shape parameters, the low-temperature crack resistance of the asphalt mortar decreased, with β having a greater effect on the crack propagation behavior than r; (3) At the mesoscale, with the increase in the crack shape parameters, there was a gradual transformation of the fracture mode from I Mode to II Mode, and the crack propagation process accelerated, resulting in a significant decrease in the low-temperature crack resistance at the macroscale. The research results establish a theoretical foundation for revealing the characteristics of multi-crack propagation in asphalt concrete under environmental influences, and offer technical support for pavement crack repair and maintenance.

Functional and structural assessment of an experimental section gap graded modified with sugarcane bagasse ash

Gap-graded aggregate combined with asphalt rubber presents a high-performance alternative for roads with heavy traffic loads, offering advantages over conventional mixtures in terms of permanent deformation (rutting), fatigue life, and texture. In this study, the conventional filler in the well-established mixture was substituted with sugarcane bagasse bottom ash (SCBA) at a proportion of 5% of the total mineral aggregates. The objective was to enhance the mechanical performance of the asphalt coating while ensuring proper disposal of this waste material. Compared to conventional filler, SCBA is less dense, has smaller dimensions, and exhibits greater roughness, thereby affecting the volumetric parameters of the Marshall mix design. Consequently, the volume of voids in mineral aggregates and voids filled with asphalt increased while maintaining the same volume of air voids (5.3%). Consequently, there was a notable increase in Marshall Stability (40%) and Indirect Tensile Test (22%) mechanical parameters. Following laboratory analysis, the modified mixtures were applied as asphalt coating on a high-traffic highway (BR-158). Field specimens revealed an 18% increase in the Resilience Modulus (4088 MPa; 3478 MPa). Additionally, its Flow Number exhibited a 73% increase (16,707; 9681), and its permanent deformation rate was 28% lower within 10,000 cycles in the dynamic creep test. This was further supported by an 11% reduction in permanent deformation rate in the Hamburg Wheel Tracking Device (HWTD) within 20,000 cycles (3.2 mm; 3.6 mm). In conclusion, the partial replacement of conventional filler with sugarcane bagasse ash within the established granulometric range has demonstrated technical feasibility both in laboratory and field settings.

A Comparative Study for the Mesoscale Models of Concrete

Abstract This paper provides an overview of mesoscale models used to simulate concrete behavior. A comparative analysis was carried out using mesoscale models with two dimensions. The impact of material type on three tests: the indirect tensile splitting test, the three-point bending test, and the direct tensile test was examined in the study. Additionally, a comparison is made between the findings obtained with and without the application of ITZ and the analysis results obtained from the direct tensile test. The results showed that the fixed crack model had higher stiffness than isotropic damage model in both direct tensile test, and three-point bending test. In indirect tensile splitting test, only fixed crack model gave meaningful results. The models with ITZ had most of the cracks in ITZ rather than in the mortar.

An alternative approach for increasing the visibility of roads

Visibility problems occur on highways that are not sufficiently illuminated at night, endangering traffic safety. Phosphor material, which has a natural glow feature under ultraviolet (UV) light, is planned to increase road visibility in areas with inadequate lighting. Phosphor powder (PP) was used in four different percentages (25%, 50%, 75%, and 100%) as fillers in hot mix asphalt (HMA), reduced to filler size. Asphalt specimens were prepared using a super pave gyratory compactor and super pave volumetric mixture design. Compacted specimens were exposed to artificial 12V UV light for 10-minute intervals in a dark room, and UV light absorption was observed. Visibility analyses were performed on the specimens by taking high-resolution photos with long exposure from a distance of approximately 30 cm from the asphalt specimen using a professional camera. According to the analysis results, the visibility values increased by 200.4%, 378.5%, 538.1%, and 728.5% compared to the reference specimen for substitution rates of 25%, 50%, 75%, and 100%, respectively. Experiments were conducted to determine the behavior of the specimens prepared as phosphorus substitutes in the mixture. After selecting the optimum binder contents, the modified Lottman test procedure was applied to measure the specimens' strength values and moisture sensitivity prepared at optimum ratios. The indirect tensile test results show that the 25% PP-substituted specimen had a better strength value. The tensile strength ratio (TSR) value, the ratio of dry and wet tensile stresses, was determined to have minor moisture sensitivity in the 50% PP-substituted specimen. HWTT was applied to the specimen containing 50% PP content, which exhibited the best TSR ratio, resulting in improved rutting performance compared to the reference specimen.

Performance of asphalt mixtures containing high reclaimed asphalt pavement and waste steel rolling oil

Reducing costs, dealing with environmental problems, and preserving more natural resources are among the main incentives for reusing asphalt instead of road reconstruction. However, asphalt reuse involves the addition of some modifiers to the asphalt mixture. In this respect, rejuvenators investigated in the previous studies did not perform properly against all failures. Besides, they had problems such as lacking access to the required amount for road construction and high production costs. Regarding the high-temperature resistance and antioxidant properties of the waste steel rolling oil (WSRO), for the first time, the effect of using this lubricant was investigated on the recovery of bitumen aging and the performance of asphalt mixture containing high amounts of reclaimed asphalt pavement (RAP). To this end, the conventional (penetration and softening point) tests and rotational viscosity test were conducted to determine the optimal amount of rejuvenator. In addition, FTIR and FESEM tests were carried out for chemical and morphological investigation. SCB and dynamic creep tests were performed on a balanced mix design to examine the performance against cracking and rutting. Moisture sensitivity was also investigated by performing an indirect tensile test. The results show that a uniform texture was created in the aged bitumen modified with WSRO, and there was a decrease in functional groups that represent the occurrence of aging. Therefore, WSRO can restore aging and improve rutting and cracking performance. Resistance to moisture sensitivity also improved. Overall, the results show a performance improvement in the mixture containing high RAP content mixed with WSRO as a waste rejuvenator. However, more studies encompassing rheological, economic and environmental aspects, are needed to conclude about the practical use of this material.

Compressed stabilised earth block synergistically valorising municipal solid waste incinerator bottom ash and sisal fiber: Strength, durability and life cycle analysis

Compressed stabilized earth blocks (CSEB) represent an eco-friendly substitute for traditional building materials, predominantly utilizing earth. Municipal Solid Waste Incineration Bottom Ash (MSWIBA) is a by-product of municipal waste treatment that can be creatively repurposed in construction projects. This research explores integrating MSWIBA as a substitute for Earth in CSEB production to conserve natural resources and repurpose waste, potentially reducing its landfill disposal. The sisal fibers (SF), often regarded as by-products of agricultural processes, offer an intriguing research material. The SF was treated with a 5 % NaOH alkaline solution to improve the CSEB bonding, increasing the flexural strength. The study aims to determine the optimal mix of stabilizers, in addition to a 10 % cement content, using various percentages of MSWIBA (10–40 % by weight of dry sand) and SF content (0.25–1 % by weight of dry soil). These blocks undergo comprehensive tests to determine their strength and durability. Wet and dry compression, flexural tests and indirect tensile tests were used to assess strength qualities, while wetting-drying cycles and acid exposure were used to determine durability. MSWIBA replaces 20 % sand in CSEB satisfying the strength. However, exceeding this amount increases void content and lowers strength, emphasizing the importance of balanced proportions for best performance. The 20 % MSWIBA and 0.75 % SF combination enhanced the compressive strength by 6.45 MPa, flexural strength by 0.92 MPa and water absorption by less than 18 %. The durability test displayed increases in compressive strength of 14.7 % and flexural strength of 93.48 % and optimized water absorption rate. Furthermore, microstructural analysis has been performed on CSEBs and the results highlight the importance of balanced cement and SF proportions for structural integrity. Life Cycle Analysis (LCA) investigation shows that construction costs using CSEB are 12.24 % higher than those with FCBs. Additionally, the study suggests that CSEB with MSWIBA and SF will be an environmentally sustainable construction material, considering factors such as energy usage, Global Warming Potential, and other environmental considerations

Study on fatigue parameters of high modulus asphalt pavement

High Modulus Asphalt Mixtures (HMAM) have gained widespread utilization in asphalt pavement construction. It is great critical to study the fatigue characteristics of HMAM. At present, various fatigue test methods are employed in indoor testing to assess HMAM under different mechanical states. Therefore, there is a critical problem that the value of fatigue parameters is not unique in the structural design of HMAM. In this study, three fatigue testing methods were initially used to address the above issues: direct tensile testing, indirect tensile testing, and uniaxial compression testing. These tests help to determine the strength yield surface states at different loading rates. And to reveal the effect of loading rate on the mechanical behavior of HMAM. The results show a power function fit and a good correlation between strength and loading rate. The relationship models of strength with speed for indirect tensile, direct tensile and uniaxial compression tests are SI=3.22(v)0.14, SD=3.22(v)0.15 and SU=3.22(v)0.12, respectively.The higher the loading rate for the three fatigue test results, the greater the expansion of the strength yield surface.The fatigue life (Nf) of HMAM underwent testing, yielding its fatigue effective stress ratio. The relationship between the two was and then established. It is found that the point (1, 1) appears on the backextension line, thus effectively complementing the conventional S-N equation. In addition, the fatigue equations for various fatigue test methods were unified based on effective stress strength ratio and the fatigue life. This paper introduces a novel method for the antifatigue design of HMAM.

Analysis of strength size effect and failure mechanism of asphalt mixtures based on discrete element method

The purpose of this study is to further investigate the strength size effect and failure mechanism of asphalt mixtures and clarify the strength parameter conversion relationship between standard and non-standard size samples. The article established an improved microscopic model for uniaxial compression and indirect tensile testing of asphalt mixtures based on laboratory and discrete element simulation tests. The effects of thickness and gradation on the uniaxial compressive strength (UCS) and indirect tensile strength (ITS) of asphalt mixtures were studied. The loading rates of the UCS and ITS tests were set at 2 mm/min and 50 mm/min, respectively. Additionally, the tensile-compressive stress distribution, crack propagation, and strength contribution rates of different contact types within the sample were investigated during the virtual model loading process. The reliability of the model was validated through laboratory test results. Finally, the strength parameter conversion relationship between standard and non-standard size samples was investigated. The study found that the UCS of asphalt mixtures decreases with increasing thickness, while the ITS increases with increasing thickness, with average reduction and increase rates of 70.69 % and 24.18 %, respectively. The contact fracture ratio and the strength contribution rate of the aggregate-asphalt mortar contacts both exceed 50 %, indicating that the fracture of these contacts is the primary cause of asphalt mixture failure. The use of small-sized samples instead of standard samples in practical applications is promising. These research work outcomes can serve as a theoretical basis for designing asphalt pavement materials and acquiring existing asphalt pavement material parameters.

The impact of seepage effect on repaired interface failure in steel bridge deck pavement: A case of pothole distress

The repeated failure of repaired interface in steel bridge deck pavement (SBDP) under complex service environment makes SBDP maintenance challenging. The primary objective of this paper was to figure out the impact of seepage on repaired interface failure, addressing the secondary damage on SBDP after distresses maintenance. A uni-body bi-material structure (UBS) specimen was fabricated to simulate the repaired interface. Besides, a simulation experimental device of hydrodynamic scouring action was put forward to evaluate the effect of cycle numbers on failure behavior of repaired interface during an indirect tensile test. In addition, numerical simulation analysis was conducted to determine the tensile stress characteristics of repaired interface under load-seepage coupling effect. Findings revealed that the failure state of repaired interface may change from brittle fracture to large deformation damage under seepage effect. The longer the duration of hydrodynamic scouring action, the more serious damage of the repaired interface, with 540 cycles resulting in an approximately 25 % reduction in interface strength. Furthermore, the stress condition of repaired interface is significantly worse when consider the coupling effect of load and seepage, approximately 40 % greater than that of a single load action. And it is closely related to its relative position with the orthotropic steel bridge deck and the actual stress conditions. The research findings presented in this paper can serve as a theoretical foundation for SBDP maintenance.

Susceptibility to moisture damage in asphalt mixes with blast furnace dust as aggregate

One of the ongoing challenges in engineering is mitigating the degradation of road infrastructure caused by water in asphalt mixes. This study aims to assess the impact of blast furnace dust, a byproduct of the steel manufacturing process, on moisture-induced damage in asphalt mixes. Three asphalt mixes were developed following the Marshall methodology: one comprising conventional crushed aggregates, while the others substituted 50% and 100% of the conventional fine aggregate with blast furnace dust. Material characterization procedures and chemical analysis of the blast furnace dust were conducted. Once compliance with the specified material requirements was verified and analyzed, water susceptibility was evaluated through an indirect tensile test across various void content levels. Similarly, leveraging the Superpave gyratory compactor, several compaction indices were determined to estimate the compaction behavior of each mix. Based on the findings, the inclusion of blast furnace dust in an asphalt mix proved satisfactory due to its contributions in enhancing tensile strength, consequently leading to a reduction in moisture-induced damage within the asphalt mix, as well as exhibiting improved compaction behavior. Additionally, this utilization contributed to diminishing the environmental impact linked to the steel production process, where substantial quantities of this residue accumulate.

Short- and long-term mechanical performances of damaged porous asphalt mixture treated with asphalt emulsion

Porous asphalt (PA) pavement usually has a short service life due to the ravelling distress. Spraying surface treatment (ST) asphalt emulsion could alleviate it. However, the effects of ST on the short- and long-term mechanical performances of PA mixture are unclear. Therefore, this study used repeated axial load test, indirect tensile fatigue test and indirect tensile cracking test to evaluate the rutting, fatigue and cracking resistances of damaged PA under different curing durations, respectively. Two curing temperatures, 25 and 60°C, were considered here. Results showed that the mechanical properties of ST treated PA were significantly improved in short-term. The durability of mechanical properties is good based on long-term observation data. The rutting resistance of treated PA was not compromised if the application rate of ST is well controlled. A high curing temperature could expedite recovery efficiency of damaged PA, but it was accompanied by faster aging, which cannot be ignored.

A model predicting mechanical properties of asphalt mixtures considering void ratio and loading conditions

The void ratio is an essential parameter in asphalt mixture design, which significantly affects asphalt mixtures' mechanical properties and road performance. The prediction model for mechanical properties will be established based on the Computed tomography (CT) scanning, strength, and fatigue test results in this research to reveal the relationship between the asphalt mixtures' mechanical properties and void ratio. Firstly, the voids' transverse and longitudinal distribution characteristics in asphalt mixtures of different gradations were investigated based on CT scanning. Then, the influences of void ratio, loading rates on the strength, and the impacts of void ratio and stress levels on the fatigue life were investigated by conducting indirect tensile tests. Finally, the mechanical properties prediction model was established for void ratio and loading conditions. Further, the feasibility of the model is verified in conjunction with existing research results. The results show that the void ratio calculated based on CT scanning is about 1.15 times the measured void ratio in the water weight method. The number of voids was uniformly distributed in the range of 15 mm∼50 mm in height and 10 mm∼40 mm in radius of the specimen. The asphalt mixtures' strength decreases with increasing void ratio and increases with increasing loading rate. The asphalt mixtures' fatigue life declines with increasing void ratio and stress level. The correlation coefficients of the established strength and fatigue prediction models were 0.963 and 0.976, respectively. The relative error between the measured strength, fatigue life, and predicted results is about 10.75% and 11.27%, respectively. This research provides a basis for designing high-performance asphalt mixtures by establishing the relationship between asphalt mixtures' microscopic and mechanical characteristics.