Toughness, as defined in ASTM D5801, is the work used to stretch a specimen until fracture, and is used to evaluate the ability of polymer modified asphalt (PMA) to resist deformation. Fracture elongations in PMA are usually longer than 10 cm. However, it is almost impossible for asphalt concrete, with or without PMA, to endure such large deformation before fracture. It is presumed that an effective elongation exists for more effective determination of toughness. Principle component analysis (PCA) and single regression analysis were used in this study to evaluate the correlation between physical tests of PMA, including toughness and performance tests of Stonic Mastic Asphalt (SMA). Meanwhile, performance tests, including resilient modulus tests, creep tests and indirect tensile tests, were conducted on SMA samples. According to the results form Principle Components Analysis (PCA), it was observed that only a common factor affects the performance tests. Regression analyses were used to find common factors from physical tests of PMA. Correlation coefficients between toughness and performance tests were found to be better than other physical tests. When toughness was calculated with effective elongation (6.5 cm), R 2 was 0.90. In our opinion, the desirable PMA should provide SMA enough work to resist the deformation while the deformation is still small. This result was also confirmed by observation of SEM and Rheological analysis. Modified toughness (calculated with effective elongation) considered as the common factor, is a simple method to evaluate the microstructure of PMA. Overall, modified toughness seems promising for use in evaluation of the effect of PMA on SMA.
This work addresses the comprehensive viscosity measurements and assessment of fluidic materials in the range from 0.01 to 2000 Poises using a fiber optical viscometer with the long-period fiber grating (LPFG) technology. The fluidic materials used and evaluated in this study were AC-20 asphalt cement, four types of silicone oils, and sunflower seed oil. We simultaneously measured the LPFG-induced discharge time and the transmission spectra both in hot air and fluidic materials (other than the AC-20 asphalt) at six different temperatures, i.e., 30, 60, 80, 100, 135, and 170 Celsius. An electromechanical rotational viscometer was also used to measure the viscosities of fluidic materialsthe silicone oils and sunflower seed oil at the above six temperatures. Comparative analysis shows that the LPFG-induced discharge time agreed well with the viscosities obtained from the rotational viscometer. The LPFG-based viscometer was capable of measuring the viscosity (discharge time) in the range from 0.12 to 2000 Poises, which is much wider than the viscosity range of a traditional electromechanical rotational viscometer. This fiber-optic LPFG-based viscometer could be proposed and implemented in the field of road and airfield pavement technology such as the viscosity measurements of asphalt cements, emulsified asphalt binders, and other viscous materials. Hopefully, such a highly sensitive viscometer is suitable for use in various fields of applications, such as civil, food, chemical and biological, mechanical, petroleum, and aerospace engineering.
In this paper, we describe the development of a viscosity sensing system using a simple and low-cost long-period fiber grating (LPFG) sensor. The LPFG sensor was extremely sensitive to the refractive index of the medium surrounding the cladding surface of the sensing grating, thus allowing it to be used as an ambient index sensor or chemical concentration indicator. Viscosity can be simply defined as resistance to flow of a liquid. We have measured asphalt binder, 100-190000 centistokes, in comparison with optical sensing results. The system sensing asphalt binders exhibited increase trend in the resonance wavelength shift when the refractive index of the medium changed. The prototype sensor consisted of a LPFG sensing component and a cone-shaped reservoir where gravitational force can cause asphalt binders flow through the capillary. Thus the measured time for a constant volume of asphalt binders can be converted into either absolute or kinematic viscosity. In addition, a rotational viscometer and a dynamic shear rheometer were also used to evaluate the viscosity of this liquid, the ratio between the applied shear stress and rate of shear, as well as the viscoelastic property including complex shear modulus and phase angle. The measured time could be converted into viscosity of asphalt binder based on calculation. This simple LPFG viscosity sensing system is hopefully expected to benefit the viscosity measurement for the field of civil, mechanical and aerospace engineering.
The study presents the comparative evaluation of mixture performance of the Superpave and dense-graded mixtures using the results of repeated shear test at constant height (RSCH), frequency sweep test at constant height (FSCH), and Hamburg wheel-tracking device (HWTD) test. The results of HWTD testing displayed the Superpave mixtures I and II were less susceptible to permanent deformation than the dense-graded mixture. The results of RSCH testing showed the cumulative shear strain and the predicted rut depths of the accumulated shear strain of the dense-graded mixture was about six times as large as those of the Superpave mixtures I and II. Compared with the test results of HWTD testing, the Superpave mixture II was less susceptible to permanent deformation and the dense-grade mixture was the most prone to rutting among these three mixtures. The normalizing frequency parameter of the dense-graded mixture was about one and half to five times as large as those of the Superpave mixtures I and II. The larger value the specification parameternormalizing frequency parameter, the less that the mixtures could exhibit performance ranking. The use of specification parameter obtained from FSCH test, normalizing frequency parameter, for assessing mixture performance was consistent with the findings from HWTD and RSCH tests. Therefore, the Superpave mixture II ranked first and the dense-graded mixture ranked third based on the overall mixture performance.
This paper presents the development and assessment of a liquid-level sensor using reflective long-period fiber grating (LPFG) technology. The LPFG was fabricated by the electrical arc discharge method and the liquid-level sensor consisted of five LPFGs in series with a reflective mirror (end) coated with silver by Tollen’s test. The experimental findings showed the sensor could be used to automatically monitor five liquid levels, such as 20, 40, 60, 80, and 100 cm. The sensing system had at least 100-cm liquid-level measurement capacity. The reflective LPFGs-in-series sensor was able to successfully yield a comparable liquid-level sensing performance and hopefully could be used in the fields of civil and agronomy engineering applications such as pipes, channels, dams, and deep-ponding paddy fields.
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