Interfacial adhesive behaviors between SBS modified bitumen and aggregate using molecular dynamics simulation

Nano-scale analysis of moisture diffusion in asphalt-aggregate interface using molecular simulations

Waste plastics have a significant impact on natural resources and the environment. The focus is on the interfacial adhesion behavior of three types of waste plastics-polyethylene (PE), polypropylene (PP), and Poly acrylic (PA)-with neutral silica (SiO2) aggregates, as well as the influence of graphene oxide (GO) on the asphalt-water-aggregate interface performance. The validity of the molecular dynamics simulations was assessed based on fundamental thermodynamic properties of asphalt, including density, glass transition temperature, cohesive energy density, and solubility parameters. The diffusion patterns of the four asphalt components on the SiO2 aggregate surface were analyzed using the mean square displacement (MSD), diffusion coefficient, and relative concentration distribution. The bonding strength between various waste plastics and the asphalt-aggregate interface was quantified by calculating the adhesion work. The results indicate that van der Waals forces and electrostatic forces play a crucial role in the adhesion between asphalt and minerals. The adhesion work between aged asphalt and aggregates is highest when PE plastic is added, lowest when PP plastic is added, and intermediate when PA plastic added. Upon introducing water molecules at the asphalt-aggregate interface, the interfacial adhesion work decreased significantly, indicating that water molecules exert a substantial negative impact on interfacial adhesion performance. However, after coating the aggregate surface with graphene oxide, the adhesion work at the asphalt-water-aggregate interface increased significantly, suggesting that graphene oxide enhances water damage resistance by improving interfacial polarity. This study provides molecular-level theoretical support for the recycling of waste plastics in asphalt-based materials and for the optimization of interfaces. Molecular dynamics simulations were performed using Materials Studio software with the COMPASS II force field. The Nose thermostat and Berendsen isobaric thermostat were used to control temperature and pressure, respectively, to maintain constant temperature and pressure conditions throughout the simulation. In non-bonded interaction calculations, electrostatic forces were calculated using the Ewald method, and van der Waals forces were calculated using the Atom Based method, with a cutoff radius of 15.5Å. The simulations were conducted using NVT and NPT ensembles, with all simulations set to fine computational precision. The constructed model was first subjected to geometric optimization (100,000 iterations), followed by annealing treatment (10 cycles with a temperature change gradient of 100K), and then the ideal molecular structure of the model was obtained through NPT ensemble simulations.

This study aims to multiscale investigate the effects of rejuvenator type, temperature, and aging degree of bitumen on the diffusion behaviors of rejuvenators (bio-oil BO, engine-oil EO, naphthenic-oil NO, and aromatic-oil AO) in aged binders. The molecular dynamics (MD) simulation method is performed to detect the molecular-level diffusion characteristics of rejuvenators and predict their diffusion coefficient (D) parameters. At an atomic scale, the mutual but partial interfacial diffusion feature between rejuvenators and aged bitumen molecules is observed. Moreover, Fick's Second Law well fits the concentration distribution of rejuvenator molecules in aged bitumen. The magnitude for D values of four rejuvenators varies from 10-11 to 10-10 m2/s, and the diffusive capacity order is BO > EO > NO > AO. Meanwhile, diffusion tests and dynamic shear rheometer (DSR) characterizations are employed to validate the MD simulation outputs. The experimental results in magnitude and order of D values agree well with MD simulation outputs. Lastly, the increased aging degree of bitumen exhibits a negative impact on the molecular diffusivity of BO, EO, and NO rejuvenators, while the D value of AO molecules enlarges as the aging level deepens. The underlying mechanism may be composed of the free volume fraction in aged bitumen and the intermolecular force between rejuvenator and aged bitumen molecules, which differs remarkably for various rejuvenators.

Comparative evaluation of moisture susceptibility of modified/foamed asphalt binders combined with different types of aggregates using surface free energy approach

Coacervation and adhesion mechanism of PEI/TA hydrogel revealed by molecular dynamics simulations.

This paper aims at evaluating the compressive strength of structural sand lightweight aggregate concrete (LWC) by the non-destructive ultrasonic pulse velocity method. To this end, a comprehensive experimental study was carried out involving more than 70 different compositions tested between 3 and 180 days with mean compressive strengths ranging from about 30 to 80 MPa and density classes from D1.6 to D2.0. The influence of several factors on the relation between the ultrasonic pulse velocity (UPV) and compressive strength was examined, including the type and binder content, type and volume of aggregates. It is found that lightweight and normal weight concretes (NWC) are affected differently by mix design parameters. NWC is more affected by the volume of aggregate and the dispersion effect caused by concrete heterogeneity tends to be lower in LWC. The prediction of the concrete's compressive strength by means of the non-destructive UPV test is analysed. Based on the dependence of the UPV on the density and elasticity of concrete, a simplified expression is proposed to estimate the compressive strength, regardless of the type of concrete and its composition. High correlation coefficients were obtained taking into account several results for different types of aggregates and concrete compositions.

Supramolecular structure of ultrathin films of hemicyanine dye bearing a crown ether group (CrHCR) was tuned by lateral pressure and investigated by means of compression isotherms, UV-vis and fluorescence spectroscopies, and X-ray reflectivity. Two different types of aggregation were revealed, depending on the absence or the presence of metal cations in the water subphase. While CrHCR forms at high surface pressures head-to-tail stacking aggregates on pure water, changing the subphase to a metal-cation-containing one leads to the appearance of well-defined excimers with head-to-head orientation. The structure of monolayers transferred onto solid supports by the Langmuir-Blodgett (LB) technique was examined by use of X-ray reflectivity measurements and molecular modeling. A model of cation-induced excimer formation in hemicyanine Langmuir monolayers is proposed. Finally, fluorescence emission properties of LB films of CrHCR can be managed by appropriate changes in the subphase composition, this last one determining the type of chromophore aggregation.

The proper disposal of steel slag has always been a great challenge for the metallurgical industry in China and around the world. In this work, the steel slag aggregate (SSA) was surface pretreated (PSSA) and applied into asphalt mixture. The adhesive behavior between the bitumen and five different types of aggregates (i.e., limestone, diorite, diabase, SSA, PSSA) were evaluated based on the contact angle and binder bond strength tests. The pavement performance of three asphalt mixtures which contain normal aggregate, SSA and PSSA respectively, was analyzed by Marshall stability test, wheel-tracking rutting test, low-temperature bending creep test and water sensitivity test. The results showed that surface modification can improve the surface properties of SSA, reduce its contact angle with bitumen, and eventually lead to the improvement of adhesion between them. In addition to the satisfied low-temperature properties, PSSA was found to significantly improve the anti-rutting property and reduce the water sensitivity of asphalt mixture. This work is expected to promote an alternative application for recycling of SSA in pavement engineering.

The diffusion of five flavor organic molecules, including D-limonene, myrcene, ethyl hexanoate, 2-nonanone, and linalool in low density polyethylene (LDPE) film were investigated by combined experimental and molecular dynamics (MD) simulation studies. The diffusion coefficients derived from the prediction model, experimental determination, and MD simulation were compared, and the related microscopic diffusion mechanism was investigated. The effects of the presence of the flavor organic molecules on the diffusion of O2 and H2O in polyethylene (PE) were also studied by MD simulation. Results show that: The diffusion of five flavor molecules in LDPE is well followed to Fick’s second law by the immersion experiment; MD simulation indicates the dual mode diffusion mechanism of the flavor molecules is in LDPE; the diffusion coefficients from MD simulation are close to those from the experimental determination, but are slightly larger than those values; the presence of the flavor organic molecules hinders the diffusion of O2 and H2O, which can be well explained from the fraction of free volume (FFV) and interaction energy calculation results derived from MD simulation.

Agents that must reach agreements with other agents need to reason about how their preferences, judgments, and beliefs might be aggregated with those of others by the social choice mechanisms that govern their interactions. The recently emerging field of judgment aggregation studies aggregation from a logical perspective, and considers how multiple sets of logical formulae can be aggregated to a single consistent set. As a special case, judgment aggregation can be seen to subsume classical preference aggregation. We present a modal logic that is intended to support reasoning about judgment aggregation scenarios (and hence, as a special case, about preference aggregation): the logical language is interpreted directly in judgment aggregation rules. We present a sound and complete axiomatisation of such rules. We show that the logic can express aggregation rules such as majority voting; rule properties such as independence; and results such as the discursive paradox, Arrow's theorem and Condorcet's paradox - which are derivable as formal theorems of the logic. The logic is parameterised in such a way that it can be used as a general framework for comparing the logical properties of different types of aggregation - including classical preference aggregation.

This paper presents the results of research focused on the modification of composition of the polymer-cement mortars. The use of these materials is quite wide. The greatest use can be found in the production of reinforced concrete repair materials. Specifically, the article analyzes problems of lightweight aggregate effect on the resistance of polymer-cement mortars to extremely high temperatures. The link is particularly evident with the risk of fire. Attention was given to the two different types of aggregates - from primary raw materials (Liapor) and alternative sources of raw materials (fly ash aggloporite). The study was carried out by the laboratory analyzing the basic material characteristics of prepared samples which were exposed to temperatures up to 1200 ° C.

To investigate the mechanical properties of recycled aggregate concrete filled square steel tubular column under bias voltage, and to analyze the effects of three influencing factors (steel ratio, eccentricity and different types of aggregates) on mechanical properties of test specimens. The experimental results indicated that recycled aggregate concrete filled square steel tubular column had high bearing capacity and excellent deformation performance, and its final fracture morphology was similar to that of common concrete-filled steel tube, which was bending failure. Steel ratio, eccentricity and different types of aggregates had significantly effects on the mechanical properties of bias column. Mid-span longitudinal strain distribution of the test specimens could basically satisfy the plane cross-section assumption, the calculated value according to standard GB 50936-2014 was close to the measured value, which was more suitable for calculating the bearing capacity of bias column.

Agents that must reach agreements with other agents need to reason about how their preferences, judgments, and beliefs might be aggregated with those of others by the social choice mechanisms that govern their interactions. The emerging field of judgment aggregation studies aggregation from a logical perspective, and considers how multiple sets of logical formulae can be aggregated to a single consistent set. As a special case, judgment aggregation can be seen to subsume classical preference aggregation. We present a modal logic that is intended to support reasoning about judgment aggregation scenarios (and hence, as a special case, about preference aggregation): the logical language is interpreted directly in judgment aggregation rules. We present a sound and complete axiomatisation. We show that the logic can express aggregation rules such as majority voting; rule properties such as independence; and results such as the discursive paradox, Arrow's theorem and Condorcet's paradox--which are derivable as formal theorems of the logic. The logic is parameterised in such a way that it can be used as a general framework for comparing the logical properties of different types of aggregation--including classical preference aggregation. As a case study we present a logical study of, including a formal proof of, the neutrality lemma, the main ingredient in a well-known proof of Arrow's theorem.

Atomistically motivated interface model to account for coupled plasticity and damage at grain boundaries

Al/Mg bimetallic composites have drawn considerable attention for their promising lightweight applications in sectors such as the aerospace and automotive industries. In these systems, the interfacial behavior critically governs the overall performance and reliability. In this research, the molecular dynamics (MD) simulation was employed to systematically study the effects of pouring temperatures (923 K, 973 K, and 1023 K) and preheating temperatures (373 K, 473 K, and 573 K) on the interfacial diffusion behavior and fracture mechanism of the polycrystalline Al/Mg bimetallic system. The results indicate that the influencing rule of pouring temperatures and preheating temperatures on the interfacial diffusion behavior is consistent. Specifically, the diffusion coefficient of Mg atoms is higher than that of Al atoms, while the diffusion distance of Al atoms is significantly greater than that of Mg atoms. As the temperature increases, the thickness of the interfacial transition layer correspondingly rises. However, the effects of these two parameters on tensile fracture behavior demonstrate notable discrepancies. Specifically, the fracture mode evolves with pouring temperature, transitioning from being mediated solely by dislocations to being co-mediated by twins and dislocations. In contrast, the fracture mechanism remains solely dislocation-controlled, regardless of the preheating temperature. In addition, all the models fractured at the interface between the diffusion layer and the Mg matrix. The optimal tensile strength of 1.850 GPa was achieved at a pouring temperature of 923 K and a preheating temperature of 473 K, representing an improvement of approximately 52% compared to the lowest value recorded in the study. This research offers significant theoretical insights for the rational optimization of preparation parameters and an in-depth understanding of fracture mechanisms in Al/Mg bimetallic systems.