Inorganic nanomaterials are widely studied to modify asphalt binder. However, the problems caused by poor compatibility and high viscosity have not been well resolved, and hence their further ...application is still limited. In order to break the limitation, this study proposes a new grafting method to optimize the surface characteristics of graphene oxide (GO), and finds that the upgraded GO when used as a modifier can significantly improve above mentioned problems. Specifically, coupling graft graphene fluid (CG-GF) was successfully synthesized via a two-step grafting method, and then properties of CG-GF were studied through Fourier infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), thermogravimetric analysis (TG), dispersion and fluidity tests. Thirdly, the prepared CG-GF was used to modify the pure asphalt binder (A-90), and the comprehensive performance of CG-GF modified asphalt binder (CMAB) was validated. Results show the modified binder doesn’t see a significant increase in viscosity above 135 °C and compatibility is not weakened. The significance of this paper is to propose a feasible method to modify the performance of inorganic nanomaterials, and this method widens the application of inorganic nanomaterial modified asphalt binders (INMAB) in pavement engineering.
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•Coupling graft graphene fluid (CG-GF) can be synthesized by the designed two-step grafting method.•CG-GF possesses liquid-like feature, and has good compatibility with A-90 asphalt binder.•CG-GF modified asphalt binder (CMAB) exhibits similar viscosity in construction temperature range compared with A-90 asphalt binder.
Asphalt fine aggregate matrix (FAM) is a predominant component directly related to field performances of hot asphalt mix (HMA), it is necessary to investigate material properties of FAM. Prior to ...preparing FAM specimens, the asphalt content was calculated by keeping the filler-bitumen (
) ratio the same as in the corresponding HMA. A non-destructive fabrication method instead of coring and cutting methods was developed to compact FAM cylinders, and the joint base was designed to be concentric with the loading axis of testing system. Rheological responses of FAM were studied using the dynamic shear rheometer (DSR). Two repeated tests prove that the FAM compactor and the jointed base meet the requirement of data validation. Results show that rheological performances of FAM are significantly affected by asphalt content, gradation, air void content, and testing frequency. Air void is concluded to be the decisive factor which influences the stability of FAM, and the fiber is demonstrated to play a role on enhancing the flow resistance of FAM-F even though with the richest asphalt content.
Although shear strength plays an important role in the performance of asphalt mixtures, it is still not adopted as a control index in traditional asphalt pavement structure design. Among most shear ...strength tests, the shape of specimen damage in the uniaxial penetration test and circle shear test proved to be more accurate in reflecting the practical asphalt pavement damage shape. To explore the impact of material composition on the shear performance of asphalt mixtures under different test conditions, uniaxial penetration tests, circle shear tests, and unconfined compressive strength tests were conducted to evaluate shear strength with considerations of asphalt mixture composition (asphalt binders, aggregate, and mineral powder). Experimental results demonstrate that the SBS-modified asphalt mixtures have a higher shear strength than conventional 70# asphalt mixtures, and the shear performance of mixtures is positively correlated with softening point of asphalt binder. For the same gradation, the shear strength of asphalt mixtures increases with the asphalt-aggregate ratio first, then decreases with the ratio increases. The shear performance of mixtures can be increased by properly increasing the maximum nominal aggregate size and reasonably adjusting the aggregate gradation. Mineral powder replaced by 20% cement or 10% PSP (phosphorus slag powder) can also satisfy the requirement. Both coarse aggregate and fine aggregate containing silt impact the shear performance of mixtures; it is recommended that the silt content of coarse aggregates is controlled within 3%, and that of fine aggregate should be within 1%.
Pavement runoff contains complex pollutants that can lead to environmental pollution and health risks. A pavement-runoff-integrated treatment system has been recognized as an effective way to deal ...with pavement runoff pollution. However, there is little support for selecting appropriate materials for physical pools due to a lack of understanding of the selective filtration and physical adsorption characteristics. In this study, gravel and activated carbon were chosen as the substrate materials for physical filtration and adsorption pools, and their corresponding purification characteristics were investigated using an indoor scaled down model. The results showed that the removal rate of all pollutants was related to the size of the gravel used. This was mainly due to the increased gravel particle size and voids, which resulted in a higher water velocity, shorter hydraulic retention time, and inadequate filtration. Compared with coconut shell granular activated carbon (GAC) and coal column activated carbon (EAC), analytically pure granular activated carbon (ARAC) showed a better removal rate for petroleum and heavy metals. This is mainly because ARAC has a larger specific surface area, higher pore volume, and wider pore size distribution, resulting in a remarkable adsorption capacity for pollutants. Overall, the combination of 0.3 mm gravel and ARAC was found to be the most suitable for use as filtration and adsorption materials for physical pools. These findings offer a gravel- and ARAC-based pavement-runoff-integrated treatment system, which has excellent potential to enhance the removal of pollutants from pavement runoff.
The optical reflection characteristics of asphalt pavement have an important influence on road-lighting design, and the macrotexture and microtexture of asphalt pavement significantly affect its ...reflection characteristics. To investigate the impact of texture parameters on the retroreflection coefficient of asphalt pavement, the texture indices of rutted plate specimens and field asphalt pavement were obtained by a pavement texture tester, including the macrotexture surface area (S1), microtexture surface area (S2), macrotexture distribution density (D1), microtexture distribution density (D2), root mean square slope (Δq), skewness (Rsk), and steepness (Rku). The corresponding retroreflective coefficient RL was measured by using a retroreflectometer. In the laboratory experiments, rutted specimens of AC-13, SMA-13, and OGFC-13 asphalt mixtures were formed. The changes in texture parameters and the retroreflection coefficient of rutting specimens before and after rolling were studied, and a factor-influence model between macro- and microtexture parameters and RL was established, along with correlation models of the texture index and RL. The results show that after the rutting test, S1, S2, D1, D2, Δq, and Rku decreased, Rsk increased, and RL increased. In the single-factor model, the parameters could be used to characterize RL with high prediction accuracy, whereas for the onsite measurements, the parameters Δq, Rsk, and Rku could well characterize RL. The nonlinear model established, based on the BP neural network algorithm, improved the prediction accuracy. This research provides ideas for optimizing the reflection characteristics of asphalt pavement and a decision-making basis for road-lighting design.
In order to study the influences of confining pressure and temperature on the shear properties of asphalt mixtures, triaxial tests were conducted at 40 °C, 50 °C, and 60 °C, with the confining ...pressure ranges from 0 to 1 MPa for the widely used continuous-graded AC (Asphalt Concrete)-13, open-graded OGFC (Open-Graded Friction Course)-13, and gap-graded SMA (Stone Mastic Asphalt)-13 asphalt mixtures in China. A nonlinear regression/prediction model of triaxial strength for asphalt mixtures was proposed. The results show that confining pressure and temperature had a significant effect on the shear resistance of asphalt mixtures. With increasing temperature, the shear strength of the asphalt mixture gradually decreased due to the decreasing of cohesion strength; the shear strength of the asphalt mixture increased with the increase of confining pressure. Meanwhile, the cohesion strength increased and the friction angle decreased gradually with the increase of confining pressure. When the confining pressure was close to 0.6 MPa, the Mohr–Coulomb failure envelope bended down, so the linear Mohr–Coulomb criterion is not suitable to describe the failure behavior of asphalt mixtures. Therefore, a power function failure envelope was put forward to characterize the nonlinear shear properties of asphalt mixtures. The nonlinear evolutional laws of shear parameters, which includes cohesion strength and friction angle, were also proposed for asphalt pavement material and structure design. Among these asphalt mixtures, the gap-graded SMA-13 asphalt mixture exhibited better performance on the resistance to shear failure, and it was recommended as the upper layer material to improve the shear performance of asphalt pavement.
Chiroptical material is an intriguing and rapidly evolving field in nanomaterial research to alter and improve the optical interaction of hybrid composites with incident light. In this regard, new ...molecular design strategies and new self-assembled structures of chiral nanoparticles (NPs) or nanorods (NRs) in composition with liquid crystal (LC) matrix have been developed for technological advancement in displays, sensors, development of hybrid materials for optical applications and others. With the emphasis on the chiroptical activities of NPs or NRs in LC systems, this review provides insight into the structure-property and composition-property relationships governing NP-LC interactions, which may point to new directions for major improvements of chiral nanomaterial research.
The strength characteristics of asphalt mixture is crucial for the design and construction of asphalt roads. A strength model considering the effect of temperature is presented in this paper based on ...unified strength theory (UST). Firstly, direct tensile tests, uniaxial compression tests and anti-shear property tests of asphalt mixture were carried out respectively at different temperatures. Key mechanical parameters were obtained, including tensile strength (
σ
t
), compressive strength (
σ
c
) and shear strength (
τ
0
) at different temperatures. Besides, the temperature sensitivity of
σ
t
,
σ
c
and
τ
0
was systematically analyzed. The results showed that the UST parameters of tensile-compression strength ratio
α
and failure criterion parameter
b
have a linear relationship with temperature
t
. A theoretical model to describe strength characteristics with the temperature of asphalt mixture was developed finally. The developed model was validated via applicability analysis. and it will provide theoretical support for the study of strength characteristics of asphalt mixture and engineering practice.
Driven by the huge thermal energy in cement concrete pavements, thermoelectric (TE) cement has attracted considerable attention. However, the current TE cement shows poor performance, which greatly ...limits its application. Herein, a series of Bi0.5Sb1.5Te3/carbon nanotubes (CNTs) co-reinforced cement composites have been prepared, and their TE properties were systematically investigated. It was shown that the addition of Bi0.5Sb1.5Te3 particles can effectively improve the TE properties of CNTs-reinforced cement composites by building a better conductive network, increasing energy filtering and interfaces scattering. The Bi0.5Sb1.5Te3/CNTs cement composites with 0.6 vol.% of Bi0.5Sb1.5Te3 exhibits the highest ZT value of 1.2 × 10−2, increased by 842 times compared to that of the CNTs-reinforced cement composites without Bi0.5Sb1.5Te3. The power output of this sample with the size of 2.5 × 3.5 × 12 mm3 reaches 0.002 μW at a temperature difference of 19.1 K. These findings shed new light on the development of high-performance TE cement, which can guide continued advances in their potential application of harvesting thermal energy from pavements.
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