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Nguyễn Gia Hào

Academic year: 2023

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The strength increased with the increase of the loading rate, and the rate of strength increase slowed down with the increase of the loading rate. Fit curve comparisons of the relationship between strength and loading rate under various loading modes.

Table 1. Test results of SBS (I-D) modified asphalt.
Table 1. Test results of SBS (I-D) modified asphalt.

Summary and Conclusions

Preparation and thermal properties of ceramsite-supported encapsulated phase change materials used in asphalt pavements.Construction. Effect of freezing solutions on tensile strength of micro- or nano-modified asphalt mixture.

Characterization of Asphalt Mixture Moduli under Different Stress States

  • Introduction
  • Sample Preparation
  • Moduli Tests
  • Test Results and Analysis
  • Conclusions

The test temperature for the dynamic modulus was 15◦C, and the stress ratio of the dynamic modulus test was 0.1. Photographs of the test rig: (a) four-point bending test, (b) indirect tensile test, (c) unconfined compressive test, (d) direct tensile test.

Table 1. The SBS-(I-D) modified asphalt performance.
Table 1. The SBS-(I-D) modified asphalt performance.

Damage Detection of Asphalt Concrete Using Piezo-Ultrasonic Wave Technology

Materials and Methods 1. Materials

Grading of AC-13 was selected and 24 samples were prepared for optimum binder percentage according to Marshall's design. One is that a 5 mm diameter cylindrical through hole was drilled in the Marshall sample. The second is that some grooves of different width were cut on the surface of asphalt beam, but the depth of grooves was the same, 15 mm.

The drying test is that all samples are placed in a 50◦C oven for 24 hours. All samples were first fully immersed in water for half an hour and then held in a vacuum saturation condition for 15 minutes. After pretreatment, the samples were frozen in the refrigerator at −18◦C for 16 hours and then taken out and placed in a bath box at 60◦C to melt for 6 hours [26].

The three-point bending test was performed on a material testing machine (WDW-T200, Tianchen, Jinan, China). The distance between the two support points was 200 mm and the loading point was located in the middle of the specimen in the longitudinal direction. Finally, the cured asphalt beams were placed in an oven at 50◦C for one hour.

Table 2. Aggregate gradation for AC 13.
Table 2. Aggregate gradation for AC 13.

Results and Discussion 1. Ultrasonic Test

In addition, the speed of the ultrasonic wave in the dry environment increases rapidly with the increase of the wavelength, the maximum data is 4027 m/s. Furthermore, with the presence of two grooves, the ultrasonic velocity decreased obviously, and the deviation of the test results was 90.74 m/s, which was very large. Furthermore, the voids in the asphalt mixture occurred around 4.5% of the volume and these voids were overfilled during the filling process.

The growth rate of microcracks was higher than the compression rate of the voids in the asphalt concrete beam. In stage 3, after 100 s, the velocity of the ultrasound wave barely changed and it had entered a stable stage. This is obvious because the displacement of aggregate and bitumen is caused by the deformation of the asphalt beam at the same time.

And the growth rate of microcracks was close to the compaction rate of the voids. In addition, the speed of ultrasonic waves in the width direction of the asphalt beam was measured before and after the three-point bending test. Based on the impact analysis, it appears that the ultrasonic speed is the result of the combined effect of temperature, ambient condition and service time.

Figure 3. Ultrasonic velocity of Marshall specimens with different environmental conditions.
Figure 3. Ultrasonic velocity of Marshall specimens with different environmental conditions.

Conclusions

Non-destructive and semi-destructive diagnostics of concrete structures in the assessment of their durability. Bull. Detection of non-emergent defects in asphalt pavement samples with long-pulse and pulse-phase infrared thermography.Eur. Nondestructive evaluation of compaction/density of hot mix asphalt with a step frequency radar: Case study on a newly paved road. Near Surf.

Evolutionary Genetic Algorithms for the Analysis of Nondestructive Surface Wave Tests on Pavements.NDT E International. In situ measurement of coating thickness and dielectric permittivity using GPR using an antenna array.NDT E Int. SASW evaluation of asphalt and cement concrete pavements using different drop heights for a spherical mass.Int.

Experimental studies in ultrasonic pulse rate of roller compacted concrete pavement containing fly ash and M-sand.Int. Damage simulation and ultrasonic detection of asphalt mixtures under the coupling effects of water-temperature-radiation.Adv. Standard Test Methods of Bitumen and Bituminous Mixtures for Highway Engineering: JTG E20-2011; Ministry of Transportation of China: Beijing, China, 2011.

Field Investigation of Clay Balls in Full-Depth Asphalt Pavement

Materials and Methods

Distance Measuring Instrument (DMI) system and Global Positioning System (GPS) were installed to obtain the accurate spatial location of each clay sphere. The distribution of clay ball within the carriageway, passing lane, shoulder and ramp was also compared. Cores with no visually observed clay sphere were also obtained to verify if there were existing clay spheres that were not exposed to the pavement surface.

Such an inspection was necessary because the existing clay ball not exposed to the surface could be the potential weak point. In the lab, such cores were cut into several pieces to investigate the existence of a clay ball. One winter after the clay ball was repaired, the researchers visited the clay ball areas again to check whether there were any newly developed clay balls or whether the previous clay ball repair was working properly.

Figure 1b is a field core from the clay ball area after cutting out the center of the hole. Two types of cores were taken: cores with clay balls and cores without clay balls from good and bad sections based on visual observation. The importance camera was placed close to the surface of the pavement, which was used to catch clay balls.

Figure 1. Field observation of clay ball. (a) Opened and cleaned clay ball; (b) sliced core from clay ball area.
Figure 1. Field observation of clay ball. (a) Opened and cleaned clay ball; (b) sliced core from clay ball area.

Results and Discussion

Skid resistance is a measure of the pavement surface's resistance to sliding or skidding of the vehicle [5-7]. Skid resistance is a function of various factors, including microtexture and macrotexture of the pavement surface. Therefore, the initial BPN value represents the slip resistance property of the pavement surface when it is fully covered with ice.

The following BPN values ​​illustrate the slip resistance when the surface is affected by ice and water. The skid resistance of the pavement surface drops at the very beginning of the ice melting process. The initial skid resistance is relatively low until the thick ice film is carried off the top of the surface by a rubber slider from the BP Tester, resulting in increasing values ​​of BPN.

Fujimoto performed a quantitative evaluation of the relationship between road surface ice thickness and skid resistance property. The stability of the skid resistance during the ice melting process at the temperature from -5◦C to 10◦C was characterized by means of a BP tester. A State-of-the-Art Review of Parameters Affecting the Measurement and Modeling of Slip Resistance of Asphalt Pavements.

Table 3. Summary of project information.
Table 3. Summary of project information.

Optimizing Gradation Design for Ultra-Thin Wearing Course Asphalt

Materials and Methods 1. Raw Materials

When designing the target mixture proportion of ultra-thin wear layer UTWC-10, the skid resistance and high temperature stability of asphalt mixture pavements must be taken into account. Determination of the optimal asphalt content in the asphalt mixture of the ultra-thin wear layer. When the asphalt content of the open friction course OGFC-7 is between 4.4% and 4.6%, the rate of change in leakage analysis loss and flight loss varies greatly.

After the test sample is removed from the mold, it should be inserted into the polishing machine wheel. The dynamic stability of the three asphalt mixtures meets the specification of not less than 3000 times/mm [17]. Figure 8 shows that the residual stability of the three asphalt mixtures meets the requirements of the specifications [17].

Since the TSR value for UTWC-10 was the highest, the water resistance of the UTWC-10 asphalt mixture was the best. It can be seen from Figure 10 that with increasing wear time, the fluctuating BPN of the three asphalt mixtures showed a significant decreasing trend. The detailed volume parameters of the three asphalt mixtures and the UTWC-10 and Novachip-B leakage test results were in Tables A1–A5.

Table 2. Properties of asphalt binder.
Table 2. Properties of asphalt binder.

Phosphors Coated with Silica–Polymer Hybrid Shell

Experiments

It is reported in the literature that persistent phosphors require pretreatment with a transparent and well-compatible silane coupling agent to improve the modification effect of the organic coating [21]. Due to the alkoxy functional groups of the silane coupling agent, which after the hydrolysis reaction produce very active hydroxyl functional groups, the first shell was formed on the surface of the persistent phosphorus. After pretreatment, the persistent silica-shell phosphors were then coated with a polymer shell from the polymerization reactions of acrylic acid (AA) and methyl methacrylate (MMA) monomers by the sol-gel method to achieve the grafting modification of the polymer shell, as shown in Figure 3 [21].

The initial doses of the silicon-polymer hybrid shell coating material are shown in Table 3 [22]. Improving the moisture resistance of persistent phosphors is the main purpose of the coating, which also greatly affects its service life. Therefore, the effects of various factors in the silica or polymer shell on the moisture resistance of persistent phosphors were investigated.

The thermal stability of the stable phosphors was evaluated by a comprehensive thermogravimetric analyzer (TGA/DSC 3+, METTLER TOLEDO, Zurich, Switzerland) in the range from room temperature to 300◦C under nitrogen atmosphere and the heating rate was 10◦C/min. Excitation and emission spectra of stable phosphors were tested by FLs980 full-function steady-state/transient fluorescence spectrometer (Edinburgh Instruments, Edinburgh, UK). Scanning electron microscopy (SEM) (S-4800, Hitachi, Japan) was used to analyze the morphological characteristics of the stable phosphors.

Table 1. Dosages of the coating with silica shell.
Table 1. Dosages of the coating with silica shell.

Results and Discussions

Obviously, KH570 is more suitable for PLO-8B luminescent powder polymer shell coating than KH560. PLO-8B luminescent powder coated with hybrid silica-polymer shell (PLO-8B-SP) was prepared to compare the moisture resistance with PLO-8B luminescent powder coated with silica shell (PLO-8B-S) and polymer shell (PLO-8B-P). Naturally, all types of shell coating significantly improve the moisture resistance of PLO-8B luminescent powder.

The moisture resistance of the PLO-8B luminescent powder coating with a hybrid silica-polymer shell was significantly improved compared to the polymer shell coating, indicating that the silica coating contributes the most to the test. Change in pH of a solution soaked with PLO-8B luminescent powder coated with a silicon polymer hybrid case. Both the polymer shell coating and the silica-polymer hybrid coating greatly improved the organic compatibility of PLO-8B luminescent powder.

TG curves of PLO-8B luminescent powder coated with silica shell, polymer shell and silica-polymer hybrid shell. FLs980 fully equipped Steady/Transient Fluorescence Spectrometer (Edinburgh) was used to measure the excitation and emission spectra of PLO-8B luminescent powder (PLO-8B) and PLO-8B luminescent powder coated with silica-polymer hybrid shell (PLO-8B-SP). Figure 16 shows XRD patterns of PLO-8B luminescent powder (PLO-8B), PLO-8B luminescent powder coated with polymer shell (PLO-8B-P) and PLO-8B luminescent powder coated with silica-polymer hybrid shell (PLO-8B-SP).

Figure 4. The change of solution pH soaked with PLO-8B luminescent powder coated with different reaction time.
Figure 4. The change of solution pH soaked with PLO-8B luminescent powder coated with different reaction time.

Hình ảnh

Figure 6. Mohr circle diagram for determining the values of C and ϕ through unconfined compressive and direct tensile strength.
Figure 7. The variation of cohesive force and internal friction angle with loading rate.
Table 8. Cohesive force and internal friction angles at different loading velocities.
Figure 8. Comparison of the relationship between strength and loading rate under various loading modes.
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