Most of the fireproof asphalt research results are applied to asphalt felt and asphalt overlay. However, the effects of the flame retardant have an adverse effect on the properties of the asphalt and they have not designed a specific flame retardant system.
Methods
Due to the shape of the tube, the sound waves propagate as flat waves inside the tube. Samples were irradiated by different lights within the wavelength range of 400-2000 nm with a step length of 5 nm, followed by detection of the reflected energy.
Results and Discussion 1. Results of the Acoustic Test
Figure 8 shows the results of heat reflection tests subjected to light at wavelengths of 400 to 2000 nm. Newly produced asphalt, which is black, has the lowest light reflectance across the entire wavelength range.
Summary and Conclusions
Laboratory research on the properties of asphalt and its mixtures modified with flame retardant.Constr. Flame retardant, thermal and mechanical properties of mixed flame retardant modified epoxy asphalt binders.Constr.
Study on Compatibility and Rheological Properties of High-Viscosity Modified Asphalt Prepared from
Low-Grade Asphalt
- Introduction
- Materials and Methods Study on Optimum Mixing Content of HVA
- Experimental Study on Rheological Properties of High-Viscosity Modified Asphalt
- Study on Viscosity-Temperature Characteristics of Low-Grade High-Viscosity Modified Asphalt
- Conclusions and Recommendations
The relationship between penetration and softening point of high viscosity asphalt prepared from asphalt with different matrix and HVA content is shown in Figure 3. The stress-strain curves of three types of matrix asphalt and high viscosity modified asphalt with 14% HVA are shown in Figure 9.
Evaluation of Asphalt with Different Combinations of Fire Retardants
Experimental Materials and Methods 1. Combinations of Fire Retardants and Asphalt
The asphalt used in this study is 70# base asphalt and the appearance of fire retardants is shown in Figure 1. The results include TG (thermogravimetric) curves and differential thermogravimetric (DTG) curves, which represent the residual mass of asphalt and the rate of mass loss, respectively. The mass loss rate represents the efficiency of mass loss during the combustion process.
Furthermore, to compare the difficulty of asphalt to burn before and after the addition of fire retardants, the decay rate of the maximum rate of mass loss was proposed. Note: The mass ratio of fire retardants is determined to be 10% of asphalt.
Numerical Analysis Model and Methods 1. Model Establishment
The surface parameters of the fire source, asphalt concrete and cement concrete are set in the "SURFACE" module. Observation points were created at different horizontal and vertical distances from the fire source to record the distribution of the temperature and smoke during the combustion process. For the smoke height, a total of 6 monitoring points were set up along the longitudinal direction of the tunnel.
In the numerical modeling, the distribution of the temperature field after combustion can directly reflect the effect of fire retardancy. Due to the flame retardants, the temperature rise would decrease, which in turn would affect the distribution of the temperature field.
Results
Figure 5 shows the typical DTG (differential thermogravimetric) curve for the asphalt with the combination of fire retardants. It can be found that the temperature approximately presented a symmetrical distribution from the center of the combustion point. Figure 7 shows a typical distribution of the temperature at the combustion point (0 m, 5 m, 10 m, 15 m, 20 m, 25 m in the longitudinal direction of the combustion point).
It can be found that the temperature increased with time and all temperatures were lower than 50 °C when 5 m away from the combustion point, indicating that the affected combustion distance along the longitudinal direction was less than 5 m. It can be seen that after burning, the smoke gradually spread to the exits on both sides of the tunnel, and the height of the smoke in the tunnel was constantly decreasing.
Conclusions
Experimental Study on Phase Transition Characteristics of Asphalt Mixture for Stress Absorbing Membrane Interlayer. Abstract: Asphalt mixtures used in stress absorbing membrane interlayers (SAMIs) play an important role in improving the performance of asphalt pavement. To investigate the rheological properties and phase transition characteristics of asphalt mixtures used in SAMI with temperature changes, twenty-seven candidate mixtures with different binders, grading types and binder contents were selected in this research.
Test results show that phase transition characteristics can better reflect the rheological properties of asphalt mixtures at different temperatures. In this article, different types of asphalt mixtures are selected to determine which is most suitable for the material in SAMI.
Materials and Methods 1. Asphalt Binder
From the literature review, it can be concluded that recent studies have mainly focused on the mechanical properties of asphalt mixtures used in SAMI, such as shear resistance and anti-fatigue performance. Investigating the phase transition characteristics of asphalt mixtures with changes in temperature is a more efficient approach to evaluate the high- and low-temperature performance and temperature sensitivity of asphalt mixtures. The grades of asphalt mixtures in this paper were classified by smooth function curves fitted through two critical control points.
Based on the function of the asphalt mixtures used for SAMI, the passing rate of the 0.075 mm sieve was set to 10% and the nominal maximum size was set to 100%. Not only the type and gradation of asphalt, but also the content of asphalt directly affects the properties of asphalt mixtures.
Results
The stiffness of asphalt mixes at low temperature is also an indication of its performance. For grade M, the stiffness of asphalt mixtures was almost the same for three asphalt types. A large number of holes can be seen on the sample of A70 grade Z asphalt mixtures.
Therefore, it can be used to evaluate the high-temperature performance of asphalt mixtures and it has a clear physical meaning. Results indicate that AR asphalt mixtures have a wider effective functional zone than the other two mixtures.
Conclusions
Regarding asphalt type, AR asphalt mixtures have a higher K value than the others, indicating that they have a smaller change of moduli. In terms of binder content, the results show that AR asphalt mixtures containing more asphalt were more sensitive to temperature changes. Finally, the effects of asphalt type, gradation type and binder content on the various indicators can be derived in Table 3.
The above five indicators can be used to describe phase transition characteristics of asphalt mixtures with temperature changes, and then a comprehensive evaluation of their performance can be made. Effect of bio-based and refined waste oil modifiers on low-temperature performance of asphalt binders. Constr.
Performance Characterization of Semi-Flexible Composite Mixture
Mix Design and Sample Preparation of SFCM
In contrast, the design of cement mortar was aimed at balancing cementitious material with high strength and good flowability. The gradation of the aggregate was designed to form a framework of the mix that allows enough space for the asphalt binder and cement mortar. The viscosity of the cement mortar was checked to determine its fluidity using the Marsh funnel method (ASTM D6910).
Following the method described in the specification, the cement mortar was prepared and tested in the laboratory using the same proportions indicated above. Figure 2a,b shows the asphalt mixture sample before and after filling, and Figure 2c shows cement mortar during filling.
Performance Testing
Three replicate specimens were tested and stress-strain relationship is shown in Figure 5 for both the SFCM specimens and the control HMA mixtures. Table 2 compares the maximum stress and work of fracture between the SFCM specimens and the HMA specimens. A summary of the test results as well as the stress-strain relationship for both the SFCM specimens and the HMA specimens is shown in Figure 6 and Table 3.
For both the SFCM mix and the HMA mix, three samples were tested and the average calculated. The test results are shown in Table 4, and the results show that the indirect tensile strength of the SFCM specimens is 12% higher than that of the HMA control specimens, indicating better rutting resistance.
Conclusions and Recommendations
Effect of cement mortars on properties of semi-flexible bituminous pavements, performance of bituminous and hydraulic materials in pavements. In Proceedings of the Fourth European Symposium on Performance of Bituminous and Hydraulic Materials in Pavements, Nottingham, UK, 11-12 April 2002. Improvement of crack resistance properties of semi-flexible pavement by cement-emulsified asphalt mortar.
Battey, R.L.; Jordan, S.W. Construction, Testing and Performance Report on the Resin Modified Pavement Demonstration Project; Transportation Research Board: Washington, DC, USA, 2007. Investigation of surface microcrack growth behavior of asphalt mortar based on the designed innovative mesoscopic test. Mater.
Effects of Aggregate Mesostructure on Permanent Deformation of Asphalt Mixture Using
Three-Dimensional Discrete Element Modeling
Materials and Methods 1. Materials
According to the Marshall mix design method based on the Chinese specifications [26], a close-graded asphalt mix, AC-20, was prepared in the laboratory. Based on the Marshall mix design method, the volumetric properties of the AC-20 asphalt mixture were determined as shown in Table 1. Aggregate less than 2.36 mm, mineral filler and asphalt binder were mixed as asphalt mastic with an asphalt content of 11.5%.
沥青玛蹄脂的气孔含量应为零，以最大限度地提高其柔韧性。
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Discrete Element Modeling of Asphalt Mixtures 1. Discrete Element Modeling
The coarse aggregate spheres within the spatial domain of the mixture model are shown in Figure 3a. The mesomechanical parameters of the stiffness model could be obtained from the macroproperties of the aggregates, as shown in equation (1) and. Asphalt mixtures exhibit a macroviscoelastic behavior due to the viscoelastic property of the asphalt mastic.
The meso Burger's model in PFC3D was well able to describe the mechanical properties of viscoelastic materials and was used to characterize the viscoelastic properties of the asphalt mastic in this study, as shown in Figure7. It has been proven that there is a conversion between the parameters of the meso Burger's model and the macro Burger's model [15,31], as shown in Equations (3) and (4).
Results and Discussion 1. Effect of Aggregate Angularity
The orientation of 4.75-9.5 mm aggregates had the greatest effect on the permanent deformation behavior of the asphalt mixtures. The aggregate skeleton was thus unstable and led to large axial deformation of the asphalt mixtures. The simulation of the uniaxial creep test performed with the DEM was able to accurately estimate the permanent deformation behavior of asphalt mixtures.
The axial deformation of the asphalt mixes was smallest when the aggregates were almost cubic. Micromechanical modeling of the viscoelastic behavior of asphalt mixtures using the discrete element method.Int.
Rheological and Interaction Analysis of Asphalt Binder, Mastic and Mortar
Results and Discussion
Similarly, SBS modified asphalt putties and mortars have a higher complex modulus compared to SBS modified asphalt binder. In general, filler addition to the SBS modified asphalt binder quadrupled the complex modulus of the putty. It should be noted that a lower value of the interaction parameter A indicates a stronger interaction between the asphalt binder and the mineral particles.
The interaction between the asphalt binder and the filler was stronger than its interaction with fine aggregates. The temperature sensitivity of mastic and mortar was therefore controlled by the type of asphalt binder.
![Figure 2. Average maximum temperature for 7 consecutive days over 30 years in certain African region (Data are from the reference [13]).](https://thumb-ap.123doks.com/thumbv2/1libvncom/9201609.0/28.723.121.605.112.500/figure-average-maximum-temperature-consecutive-certain-african-reference.webp)
