Incorporating iron tailings (ITs) into asphalt represents a new method for waste-to-resource conversion. The objective of this study is to evaluate the fatigue performance of ITs as fillers in ...asphalt mastic and investigate the interaction and interfacial adhesion energy between asphalt and ITs. To achieve that, the particle size distributions of two ITs and limestone filler (LF) were tested through a laser particle size analyzer; the morphology and structure characteristics were obtained by scanning electronic microscopy (SEM), the mineral compositions were conducted through X-ray diffraction (XRD), and the chemical compositions were tested through X-ray Fluorescence Spectrometer (XRF). Furthermore, the fatigue properties of asphalt mastic and the interaction between asphalt binder and mineral fillers (ITs and LFs) were evaluated by Dynamic Shear Rheometer (DSR). The interfacial adhesion energy between ITs and asphalt binder were calculated through molecular dynamics simulation. In the end, the correlation between the test results and the fatigue life is established based on the gray correlation analysis, the environmental and economic benefits of iron tailings asphalt pavement are further evaluated. The results show that the particle size distribution of ITs is concentrated between 30 μm and 150 μm, and the main component is quartz. ITs have rich angularity and a higher interaction ability with asphalt. The adhesion energy of iron tailings filler to asphalt is less than that of limestone. The correlation degree of the interfacial adhesion energy and interaction between asphalt and mineral filler with asphalt mastic fatigue life is close to 0.58. Under the combined action of interaction ability and interfacial adhesion energy, the fatigue life of IT asphalt mastic meets the requirements. ITs as a partial replacement for mineral fillers in asphalt pavement have great environmental and social effectiveness.
To evaluate rutting based on driving quality of vehicles, three pavement models were established in view of the morphological characteristic of pavement ruts and friction coefficients, and the ...control models of vehicles conducting the braking were established according to different driving conditions. Lateral acceleration, roll angle, yaw angle, and lateral offset were adopted to describe the driving quality and safety of vehicles. The effects of different rut depths and width–height ratios on driving quality of vehicles under different driving conditions were analyzed. Results show that when a vehicle drives across a rut on a dry pavement at a speed of 100 km/h, the rut depth should be less than 20 mm to ensure the driving stability of vehicle. Road engineers and researchers should pay attention to this situation that width-height ratios of sidewall are 1 or smaller. When one wheel of a vehicle is braked in a rut groove with water, the driving speed of vehicles should be strictly controlled within 120 km/h, and the rut depth for road with a high driving speed should be less than 10 mm to ensure the driving stability and safety. The presented findings may make a contribution to maintenance decision-making.
This study aims to develop a new index to evaluate the low-temperature cracking performance (LTCP) of recycled asphalt mixtures. To achieve this, the assumption that fracture energy has limitation in ...evaluating the LTCP of mixtures was put forward firstly. To reveal this limitation theoretically, a concept of energy absorption rate that characterized the fracture energy of the mixtures was then given. Thirdly, an equivalent fracture temperature (EFT) corresponding to the critical cracking temperature in a thermal stress restrained specimen test (TSRST) was proposed to evaluate the LTCP of mixtures based on a three-point bending beam (3PBB) test. Finally, some data derived from previous work were collected to verify the proposed assumption, and the 3PBB test and TSRST were conducted to investigate the LTCP of five recycled mixtures with different reclaimed asphalt pavement (RAP) material contents and to verify the rationality of the proposed EFT. The results confirmed that fracture energy had some limitations in predicting the LTCP of mixtures. The EFT was as accurate as the critical cracking temperature in evaluating the LTCP of mixtures. Compared to fracture energy and critical cracking temperature, EFT had bigger absolute change and relative change between different mixtures, meaning it was better to differentiate the LTCP of mixtures. Compared to failure strain, EFT was also more definite and less variable when processed by different data analysts, meaning it was more objective.
The thermodynamic property of asphalt binder is changed by the addition of crumb rubber, which in turn influences the self-healing property as well as the cohesion and adhesion within the ...asphalt-aggregate system. This study investigated the self-healing and interface properties of crumb rubber modified asphalt (CRMA) using thermodynamic parameters based on the molecular simulation approach. The molecular models of CRMA were built with representative structures of the virgin asphalt and the crumb rubber. The aggregate was represented by SiO 2 and Al 2O 3 crystals. The self-healing capability was evaluated with the thermodynamic parameter wetting time, work of cohesion and diffusivity. The interface properties were evaluated by characterizing the adhesion capability, the debonding potential and the moisture susceptibility of the asphalt-aggregate interface. The self-healing capability of CRMA is found to decrease as the rubber content increases. The asphalt-Al 2O 3 interface with higher rubber content has stronger adhesion and moisture stability. But the influence of crumb rubber on the interfacial properties of asphalt-SiO 2 interface has no statistical significance. Comparing with the interfacial properties of the asphalt-SiO 2 interface, the asphalt-Al 2O 3 interface is found to have a stronger adhesion but a worse moisture susceptibility for its enormous thermodynamic potential for water to displace the asphalt binder.
Rutting is a major distress occurring in the service life of the asphalt pavement, especially in hot weather areas. A laboratory-produced specimen is widely used for rutting performance evaluation ...which may not be completely represented by the field situation. The objective of this study is to evaluate the rutting performance of field specimens from the Chongqing highway by utilizing the Hamburg wheel-tracking test (HWTT) and dynamic modulus test. Different test conditions were conducted on the HWTT by investigation of the actual local weather condition. The results showed that rutting depth was different under different test conditions, and 10000 loading cycles were recommended as the maximum loading cycles. Particularly, several factors that influence the rutting depth were investigated, and the specimen height of 6 cm is more appropriate for the HWTT. Additionally, different test conditions were proposed as the HWTT test condition for different asphalt concrete (AC) layers in the Chongqing area. Rutting contribution of each AC layer to the pavement structure was analyzed. Moreover, the dynamic modulus at 54.4°C, 5 Hz and 54.4°C, 1 Hz could effectively represent the rutting performance of the asphalt mixture, and the dynamic modulus test is recommended for the rutting performance evaluation of the full-thickness AC layer.
Crack sealing with hot-applied sealant is a widely used technology for asphalt pavement crack repair, but the sealant usually occurs bond failure at an early stage. Due to the research on the ...mechanical changing characteristics of crack sealant bonding interface is insufficient, the systematic analysis and explanation for the early failure phenomenon is lack. Based on this, a 3D finite element (FE) model of asphalt pavement with crack repair structure is established to study the dynamic behavior characteristic of crack sealant. Firstly, the dynamic response characteristics of the crack sealant bonding interface under different repair groove sizes and forms are systematically analyzed. Then the recommended repair groove size range is given accordingly. Secondly, the effects of different vehicle speeds and axle loads on the dynamic response of the crack sealant bonding interface are analyzed. The results show that lower vehicle speeds and higher axle loads result in higher stress levels at the crack sealant bonding interface, the sensitivity of tensile stress to vehicle speed and axle load is higher than that of shear stress. Finally, the temperature stress field of the repair structure is used as a predefined field and imported into the 3D FE model. The dynamic response of crack sealant bonding interface under thermal-mechanical coupling is analyzed. The results show that the tensile stress of bonding interface is mainly affected by temperature conditions, and the vehicle load is the primary factor affecting the level of shear stress. The research findings provide a scientific insights and guidance for the evaluation of crack sealant performance and the improvement of crack repair technology.
•The recommended repair groove size range was given.•The influence of thermal-mechanical coupling was evaluated.
It is common for reinforced concrete in the saline region to bear fatigue loading and chloride induced corrosion, which has become one of the main causes of structural failure of reinforced concrete. ...The objective of this paper is to investigate the characteristics of chloride ion transport in concrete under fatigue loading. A new theoretical model describing the chloride ion transport in saturated concrete under fatigue loading is proposed. In this model, the concrete is divided into two parts, matrix and microcrack, to characterize the chloride diffusion coefficient of concrete based on crack area. The influence of fatigue damage on the microcrack area of concrete is quantitatively analyzed and the relationship between fatigue loading and chloride diffusion coefficient is established. Then, based on Fick’s second law, the model is proposed and solved by analytical solution. Some experiments are conducted to verify the proposed model and the simulated and measured results are in good agreement with each other. Finally, the characteristics of chloride ion transport under different influencing factors are analyzed using the proposed model.
The dynamic modulus of semi-rigid material is one of the important material parameters widely used in the design and evaluate of asphalt pavement, which has a great effect on the reliability, healthy ...condition and service life of pavement. To show the three-phase degradation process of dynamic modulus accurately and calculate the time-dependent reliability based on fatigue damage, the degradation models based on non-linear fatigue damage and improved Wei-bull distribution modulus degradation are established and testified in this paper, considering the threshold of normalized modulus. Then the reliability models based on the two above degradation process models are evaluated. Finally, the reliability analysis procedure is established using Monte Carlo (MC) method and the corresponding calculation is conducted using Matlab. Cement stabilized macadam is used as an example in this paper. Results show that non-linear fatigue damage and improved Wei-bull distribution modulus degradation models can indicate threephase degradation process of semi-rigid material modulus better and the reliability based on the proposed two models was more accurate to the actual situation.
The combination of pavement rutting, poor road alignment, and extreme adverse weather will seriously threaten the driving safety of vehicles, whereas only a few of these factors are commonly ...concerned. This study aims to efficiently evaluate the impacts of various driving conditions on the lateral stability of the vehicle and produce a practical recommendation for pavement maintenance in what concerns rutting. A systematic framework was, thus, developed to conduct a comprehensive evaluation of the lateral stability of the vehicle, which incorporates a single-factor test and multi-factor test based on the stability indicators obtained from Carsim simulations. The vehicle road weather model was established in the Carsim software by considering seven factors, including driving speed, width–height ratio (WHR) of rutting sidewall, radius of circular curve, superelevation, crosswind angle, crosswind speed, and friction coefficient, respectively. The results show that the established framework behaves with satisfactory performance, regarding evaluating the effect of various impact factors on the lateral stability of the vehicle while driving across rutting. Stability indicators suddenly fluctuate in a short time, due to the instantaneous wandering behavior of crossing rutting. Additionally, the sudden fluctuation phenomenon is greatly enlarged, and the vehicle is inclined to occur with lateral instability when WHR equals 5, particularly in roll-over instability. It is recommended to concurrently confine the WHR greater than 10 and friction coefficient greater than 0.4, in order to ensuring driving stability. The multi-factor test revealed that the vehicle speed and WHR of the rutting are leading factors that affect driving stability, followed by the radius of circular curve, superelevation, crosswind angle, crosswind speed and friction coefficient, respectively, which are both essential factors for driving stability. The outcomes of this study may contribute to supplying guidelines for controlling key adverse conditions and making decisions on pavement maintenance.
High-elasticity anti-rutting additives, one of the most promising modifiers of asphalt mixtures, were commonly utilized for mixtures by mixing with aggregates directly. However, their interaction ...with the asphalt binder and their modification mechanism remain unclear. Accordingly, to understand the rheological behavior of asphalt binder modified with high-elasticity anti-rutting additives, three additives were added into asphalt binder to prepare high-elasticity modified asphalts (HEMAs) via a high-speed shear mixer, and the typical attributes of viscoelastic properties were investigated by the rotational viscosity (RV) test, frequency sweep test, as well as bending beam rheometer test. Following that, the relation between the macro-rheological behavior and microscopic mechanism was incorporated by applying Fourier transform infrared spectroscopy (FTIR), atomic force microscope (AFM), and fluorescence microscopy (FM) analysis, respectively. Results indicate that the incorporation of high-elasticity additives into base asphalt causes a remarkable increase in RV along with a decline in temperature susceptibility. Likewise, a higher proportion of elasticity behavior is indicated for HEMAs, for which the wider temperature range of elasticity dominance also occurs. Regarding modification mechanism, the interaction between the asphalt and additives is physical co-blending, without new characteristic peaks appearing in FTIR spectrum. The AFM test reveals the grouping effect of “bee-structures” conduces the agglomeration of wax crystals and macromolecular components, thus increasing the elasticity and RV of HEMAs. However, the poor compatibility between the ARA-U additive and asphalt leads to unsatisfactory low-temperature performance. Significantly, a large area percentage of “sea-island structure” implies better compatibility of ARA-N, which strongly confirms the existence of the plateau region in master curve. It recommends employing anti-rutting additives that are compatible with the asphalt and enable moderately increase its elasticity, which ensure considerable entanglement and sufficient network in the asphalt-additive system, so that balanced performance can be achieved for the asphalt binder.
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