Untreated and acid-treated multi-walled carbon nanotubes (MWNT) were used to fabricate MWNT/epoxy composite samples by sonication technique. The effect of MWNT addition and their surface modification ...on the mechanical properties were investigated. Modified Halpin–Tasi equation was used to evaluate the Young’s modulus and tensile strength of the MWNT/epoxy composite samples by the incorporation of an orientation as well as an exponential shape factor in the equation. There was a good correlation between the experimentally obtained Young’s modulus and tensile strength values and the modified Halpin–Tsai theory. The fracture surfaces of MWNT/epoxy composite samples were analyzed by scanning electron microscope.
•The purpose here focused on Microwave heating and healing of asphalt mixture.•Nano-graphite (NG) enhanced the heating rate of asphalt concrete.•The NG increased the microwave healing index (HI) of ...broken samples under the IDT test.•The specific heat capacity of aggregates is an influential part of asphalt mixtures' heating and energy consumption.•Healing Index was affected by aggregates type, the content of NG, and rest time.
This paper aimed to investigate the effect of nano-graphite (NG) as a conductive additive and specific heat capacities of aggregates on the self-healing performance of the asphalt mixtures. In this research, three types of aggregates, including Limestone, Granite, and Dolomitic Limestone, with different contents of NG (5%,10%, 20%, and 30% by the weight of bitumen) were used. The indirect tensile tests (IDT) were applied to evaluate the microwave healing capability of broken samples. The healing index (HI) analysis showed that the optimum amount of NG was 10% by weight of bitumen, which restored tensile strength in healed samples above half of their original strength. Also, it was found that among the mixtures containing optimum NG, the sample with Granite aggregate consumes 16% and 30% less heating energy than samples with Dolomite Limestone and Limestone aggregates, respectively. In addition, results indicated that the HI of broken samples in the 24-hour rest period at ambient temperature has increased by 15 to 30 % compared to the 12 h.
•FEM was employed to extract the critical response function of flexible pavement.•The required data were determined using analytical method, WIM, and field studies.•The modified gaussian function is ...best fitting equation to critical responses.
Accurate and realistic identification of critical response of pavement structure leads to sustainable pavement structure design. This study aimed to obtain and analyse the rutting critical response function under heavy trucks using Abaqus three-dimensional finite element and particle swarm optimization (PSO) methods. For modeling, asphalt viscoelastic properties, data of the Weigh-In-Motion (WIM) device, and the Moving Load method were used to simulate trucks passing over the pavement. The thickness of pavement layers and their elastic and viscoelastic properties were calculated by field study and theoretical relationships, respectively. The truck specifications including loads, axles and wheels configurations, and dimensions were collected by WIM data and field survey. The results showed that the best statistical equation that could be fitted to critical responses was the modified Gaussian function. Also, according to analysis results, the effect of truck speed on the rutting critical responses was greater than its weight.
•The PHEMA modifier significantly affects the healing potential of bitumen.•The results show that the trends of fatigue life logarithm are almost equal to the healing indices trends.•NMR tests of ...RTFO-aged modified samples show the highest slope of healing.•Aging effects on self-healing capability are decreased in modified bitumen.•The healing indices are between 0.26 and 4.45 for all the healing tests.
This research study aims to investigate fatigue and self-healing performance of poly 2-hydroxyethyl methacrylate modified bitumen using Linear Amplitude Sweep, Time Sweep, Fourier-Transform Infrared Spectroscopy, Scanning Electron Microscope and Nuclear Magnetic Resonance tests and healing indices. Results show that modifying virgin bitumen with PHEMA expands the aromatic part of the binder. NMR and FTIR results show aging effects on healing capability are reduced by PHEMA addition. Also, the results show that healing indices are between 0.26 and 4.45. The comparison of HI indices trends with Nf trend shows that the PHEMA%-Log (Nf) trends are almost equal to the PHEMA%-HIFTIR&NMR trends.
In this study, Mg–2 wt% Zn scaffolds were fabricated by the powder metallurgy method, and the effects of the porosity content on the microstructure, and the mechanical properties of the scaffolds ...were studied. Nanocomposite coatings were deposited by pulse electrodeposition (PED) method on Mg–2Zn scaffolds and studied using a scanning electron microscope (SEM), X-ray diffraction (XRD), energy-dispersion spectrometer (EDS), and Fourier transform infrared spectroscopy (FT-IR). The coatings morphologies showed that optimal coating was obtained at 40 V pulse voltages, 10 min coating time and nanohydroxyapatite(nHA)/chitosan (CS) ratio = 10. The pulse-peak current density (CD), the pulse duty cycles (DC), pH and temperature were considered 10 mA/cm
2
, 0.2,7 and 37 °C, respectively. In optimal coating, Ca/P atomic ratio was obtained at 1.57, which is similar to the value of bone hydroxyapatite. The corrosion resistance and thermal stability of optimal coating were examined by potentiodynamic polarization and thermogravimetric analysis (TGA), respectively. The results showed that the corrosion rate of the optimal coating was 0.58 mm/year, which is very low and appropriate in compared to the Mg–2Zn with a corrosion rate of 2.09 mm/year. The TGA results indicated that the significant weight loss is about 23% and 14% for CS and optimal coating, respectively. The in vitro biocompatibility of the optimal coating was evaluated by cell adhesion, cytotoxicity, and alkaline phosphatase (ALP) assays using MG63 cells. The results indicate that the optimal nanocomposite coating was highly biocompatible, making this material more suitable for applications in bone tissue engineering and to repair bone defects caused by sports injuries.
The similar mechanical properties of magnesium and its alloys to natural bone, along with their appropriate biodegradability, make them promising candidates for orthopedic implant applications. ...However, there are concerns regarding their poor corrosion resistance. In this study, a double-layer coating of ceramic-polymer (nHA/PLGA) was applied to Mg to address this challenge. In the first step, the hydroxyapatite coating was deposited using the electrodeposition method. The poly(lactic-co-glycolic) acid coating was then applied to the coated samples using the dip method. Scanning electron microscopy of the samples reveals a uniform double-layer coating with a thickness ranging from 20 to 30 μm. The mechanical properties of the coatings were examined through the indentation testing, which revealed a higher degree of adhesion of the double-layer coating to the substrate. Potentiodynamic polarization of the double-layer coating indicates an increase in the corrosion potential from −1.82 to −1.4 V and a decrease in the corrosion current from 2.3 to 0.37 μA/cm2. Moreover, the MTT assay of double-layer coated samples showed an increase in cell proliferation near the 48-h extract of the samples. This indicates a decrease in the release of ions from the surface of magnesium when this coating is applied.
This paper aimed to investigate the effect of Nano-TiO
2
as a semi-conductor additive on the pollutant's absorption of a micro-surfacing layer. In this research, micro-surfacing samples with Nano-TiO
...2
values of 5, 7, 9, 11, and 13% (by weight of bitumen) and two types of aggregates (immersed and non-immersed aggregates in Nano-TiO
2
) were tested to determine contaminant absorption and evaluate rutting performance at two temperatures of 20 and 40°C. The results revealed that NO
X
absorption improved with increasing Nano-TiO
2
, reaching 40% in samples with the optimal amount of Nano-TiO
2
(11% by weight of bitumen). Wheel track test results showed that the optimum sample had a better performance compared to the control sample. Also, it was observed that the absorption of pollutants decreased after conducting the wheel track test.
Well-ordered and surface engineered hierarchical hydroxyapatite microspheres (HAM) were prepared via a template free hydrothermal process. Ethylene diamine tetra (methylene phosphonic acid) (EDTMP) ...was used as chelating or regulating agent for the first time in this study. The results indicated the formation of sheet-like particles in the absence of EDTMP. On the other hand, microspheres with radially grown nanorods (HAMNR) or nanosheets (HAMNS) on the surface were obtained (with average diameter of 5 µm) in the presence of EDTMP. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to characterize the crystalline phases in the synthesized samples. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that EDTMP concentration played an important part in regulating the morphology to form well organized microspheres with nanosheets or nanorods on the surface. Brunauer-Emmett-Teller (BET) revealed an increase in the specific surface area with the change in morphology from the HAMNS to HAMNR. Possible mechanisms are proposed to account for the formation of different morphologies based upon thermodynamic and kinetic theories.
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This study aimed to evaluate the effect of mastic specifications on the intermediate and low temperatures performance of hot mix asphalt. In this research study, four different asphalt mixtures were ...fabricated with two types of aggregate and bitumen at three different mastic densities (defined as F/B ratios). At intermediate temperature, Four-Point Bending (4PB) beam fatigue tests were carried out at 8 Hz frequency and the strain levels of 460, 750, and 1100 microstrain. Also, the low-temperature performance of mixtures was evaluated by using Semi-Circular Bending (SCB) tests at −6°C, −18°C and −12°C, −24°C for PG 64-16 and PG 58-22 fabricated mixtures, respectively. Fatigue test results showed that the fatigue life of asphalt mixtures was more influenced by the mastic density at the lower strain level. Moreover, a minimum mastic density was necessary for improving fatigue performance. The SCB test results revealed that increasing the mastic density makes higher values in the mixture's fracture energy, fracture toughness, cracking resistance index (CRI), and tensile strength. Also, the low-temperature performance of asphalt mixtures containing aggregate with a high abrasion value (AAV) was more dependent on the mastic density.
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