Abstract
In order to study dynamic characteristics of warm mix foamed asphalt mixture in seasonal frozen area, cylinder dynamic modulus test of four kinds of mixture with two gradations and three kinds of asphalt was carried out by UTM-100. Then, the effects of test temperature, loading frequency, and foaming water consumption on dynamic modulus were analyzed. Finally, the compressive resilient modulus trial was made to compare mechanical properties. Results show that dynamic modulus for warm mix foamed asphalt mixture increases with rising temperature and decreased frequency. The inflection points of the dynamic modulus vs frequency curves at low temperature, normal temperature, and high temperature are 2 Hz, 10 Hz, and 15 Hz, respectively. Static modulus of SBS# modified and nonmodified warm mix foamed asphalt mixture is corresponding to the dynamic modulus 0.001 Hz–0.1 Hz and 0.00001 Hz–0.05 Hz. The effect on gradation type on the dynamic modulus of asphalt mixture is AC-20 > AC-13, and the degree of sensitivity of the water consumption to the master curve equation of dynamic modulus under different gradations is AC-13 > AC-20.
Highlights
Considering that there are not many research institutions and test section paving for warm mix foamed asphalt mixture in China, only Hebei, Liaoning, and other places have carried out related research, there are certain indoor and experimental roads in terms of road performance [10,11,12]. ere are few research studies on dynamic characteristics, especially after the promulgation of JTG D50-2017 for Highway Asphalt Pavement Design Specification; asphalt mixture design uses dynamic modulus, so it is necessary to study the dynamic modulus of warm mix foamed asphalt mixture under the condition of seasonal frozen zone, in order to provide design basis for highway industry research and road construction personnel
Compared with the stillness springback modulus, the dynamic modulus can better reflect the change of the stress of asphalt pavement under dynamic load, which has been paid much attention by many scholars at home and abroad [13,14,15]. |E∗| is the ratio of stress peak σ0 to strain peak ε0 in the modulus test, and dynamic modulus |E∗| and phase angle φ at specific temperature and frequency conditions can be obtained by the dynamic modulus test, in order to better describe the stress and strain under the action of sinusoidal load, different loading frequencies, and different temperatures; at any time of the change law, the specific calculation formula such as (1)∼(2), wherein Ti is the lag time between stress and strain, Tp is the period of time stress
By panning the corresponding dynamic modulus at the original frequency to the corresponding frequency at the reference temperature, that is, reduced frequency, in which the relationship between the shift factor and the reduced frequency is shown in formula (3), the method of the shift factor is numerous, and in this paper, the Arrhenius equation [17] is selected for fitting calculation (formula (4)) and for the dynamic modulus main curve determination using the sigmoidal model [18] to fitting (formula (5)), and formula (3) after the logarithm, combining formula (4), can get the dynamic modulus of the main curve equation (formula (6)): fr α(T), f log(α(T))
Summary
Compared with the stillness springback modulus, the dynamic modulus can better reflect the change of the stress of asphalt pavement under dynamic load, which has been paid much attention by many scholars at home and abroad [13,14,15]. |E∗| is the ratio of stress peak σ0 to strain peak ε0 in the modulus test, and dynamic modulus |E∗| and phase angle φ at specific temperature and frequency conditions can be obtained by the dynamic modulus test, in order to better describe the stress and strain under the action of sinusoidal load, different loading frequencies, and different temperatures; at any time of the change law, the specific calculation formula such as (1)∼(2), wherein Ti is the lag time between stress and strain, Tp is the period of time stress. Due to the limitations of the test methods and test equipment, it is not possible to test the dynamic modulus of the asphalt mixture over a wide temperature and time, for which a dynamic modulus master curve is introduced. E core of the dynamic modulus master curve lies in the timetemperature equivalent principle of the mixture [16], and the key to the time-temperature equivalent principle lies in the determination of the shift factor. By panning the corresponding dynamic modulus at the original frequency to the corresponding frequency at the reference temperature, that is, reduced frequency, in which the relationship between the shift factor and the reduced frequency is shown in formula (3), the method of the shift factor is numerous, and in this paper, the Arrhenius equation [17] is selected for fitting calculation (formula (4)) and for the dynamic modulus main curve determination using the sigmoidal model [18] to fitting (formula (5)), and formula (3) after the logarithm, combining formula (4), can get the dynamic modulus of the main curve equation (formula (6)): fr α(T), f (3). Where fr is the reduced frequency at the reference temperature, Hz; f is the test frequency, Hz; α(T) is the shift factor, which represents the translation distance from the dynamic modulus curve to the reference temperature at the temperature of the main curve; ΔEa is the activation energy; R is the general gas constant, 8.314 J/(K mol); T is the test temperature, K; Tr is the reference temperature, K; δ is the logarithm of the minimum dynamic modulus |E∗|min; α is the logarithm of the maximum dynamic modulus |E∗|max; and β and c are the regression coefficients
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