Papers by Keyword: Dynamic Modulus

Abstract: In this paper, the dynamic characteristics for three different kinds of copper tailings are studied through a series of cyclic triaxial tests. It is found that under confining pressure 200 and 300 kPa, elastic modulus raises with the increasement of coarse grain content to a certain degree and then declines, and the maximum elastic modulus corresponds to good gradation. While, as for confining pressure 100 kPa, elastic modulus raises with the increasement of fine grain content. It is also found that elastic modulus raises with the increasement of confning pressure. And, damping ratio raises with the increasement of shear strain and finally to a stable value. Finally, the fitting G_d/G_dmax~ curve for three kinds of tailings shows the reasonableness of test results.

Abstract: Viscosity test, dynamic shear test, dynamic modulus test and creep test were conducted to investigate the rheological properties of high modulus asphalt and its mixture. Test results indicated that the viscosity of hard grade asphalt could be increased when compared with the ordinary asphalt, especially at high temperatures. The complex shear modulus and dynamic modulus of hard-grade asphalt binder and its mixture were increased, which implied that the stiffness of them was enhanced. Furthermore, the elastically portions for viscoelastic property of asphalt binders were increased, which resulted in the reduction of phase angle for hard grade asphalt binders and mixtures. The rutting parameter for hard-grade asphalt mixture was increased remarkably, which revealed that the resistance to permanent deformation could be significantly improved for hard grade asphalt mixture.

Abstract: In order to analyze the characteristics of high modulus asphalt mixture dynamic modulus, Universal Testing Machine (UTM-25) was used for dynamic modulus test of three kinds of mixtures, which were PR Module modified asphalt mixture and PR PLAST.S modified asphalt mixture and virgin asphalt mixture, to investigate dynamic modulus and phase angle at different temperatures and frequencies. The results indicate that: the dynamic modulus order of the three asphalt mixtures is PR MODULE > PR PLAST.S > Virgin. PR MODULE asphalt mixture dynamic modulus is much larger than the other two.

Abstract: This study focused on the performance of the Large Stone Permeable Asphalt Mixture (LSPM) with neat asphalt and its feasibility to use as asphalt pavement flexible base. For comparision, LSPM mixtures were designed respectively with neat 60/70-grade asphalt and modified asphalt and the performance of LSPM was studied and compared by volume index test, draindown test, Hamburg Wheel-tracking Test and dynamic modulus test. The results showed that the performance of LSPM with modified asphalt was superior to LSPM with neat asphalt and cellulose fiber, but draindown and rutting performance of LSPM with neat asphalt met requirements of corresponding specification and dynamic modulus of LSPM with neat asphalt had the same characteristic with LSPM with modified asphalt, which proven that LSPM with neat asphalt can use as asphalt pavement flexible base by properly mix design and pavement structure design.

Abstract: To study the dynamic modulus characteristic of LSPM mixes, dynamic modulus test was conducted for Large Stone Permeable Asphalt Mixtures (LSPM ) with neat asphalt and with modified asphalt and the range of dynamic modulus values for LSPM was determined and the dynamic modulus master curves were developed. The magnitude of the dynamic modulus decreased with an increase in temperature and increased with an increase in the frequency. The phase angle decreased as the frequency increased at low temperature. With temperature increase, there was a transition interval, where the phase angle increased up to frequencies of 0.5 Hz, and then it started to decrease as frequency increased. After the transition interval, the phase angle increased with an increase in frequency. Master curves developed by sigmoidal function showed that LSPM with modified asphalt exhibited higher dynamic modulus values at middle and high frequencies and lower dynamic modulus values at low frequencies.

Abstract: Pavement design adopts the static index pavement design method; it has significant limitations for flexible asphalt pavement. This paper proposes asphalt mixture dynamic modulus determination method on the basis of existing research results at home and abroad. Dynamic modulus effect is studied on the mechanical properties of flexible base asphalt pavement, and the flexible base asphalt pavement performance is preestimated by the use of the dynamic modulus indicators in the paper.

Abstract: The fitting models of dynamic modulus of asphalt mixtures were studied in this paper. UTM dynamic modulus tests were adopted to determine the dynamic modulus of two asphalt (A, B) mixtures. Then, the WLF equation and Arrhenius formula, based on the time-temperature equivalence principle, were used to get the shift factors and master curves of asphalt mixtures. Combined with Sigmoidal model and CAM model, it was founded that the Arrhenius formula was more suitable to get the master curves of asphalt mixtures. What is more, the CAM model was more suitable to fit master curves of both asphalt mixtures.

Abstract: An experimental measurement of dynamic properties, including dynamic modulus and phase angle, of asphalt mixtures with varying saturation levels of moisture has been carried out in the study. The specimens of asphalt mixture were compacted with three different air void contents and two different levels of moisture saturation. The relaxation modulus expressed by Prony series was estimated from the Prony series expression of dynamic modulus. The purpose of this study is to identify the effect of air voids on dynamic properties that affect and control moisture susceptibility of asphalt mixtures and then compare the stress relaxation behavior of asphalt mixtures between dry and moisture conditioning. The results show that dynamic properties are quite sensitive to temperature and loading frequency in dry and different saturation levels of moisture. Moreover, and the smaller the air voids and saturation level, the greater the increase in dynamic modulus and rate of stress relaxation, indicating better resistance to cracking and less moisture susceptibility.

Abstract: To evaluate the pre and post change of structure strength of old asphalt pavement field hot regeneration, we use the portable falling weight deflectometer method (PFWD) and benkelman beam method (BB) respectively to do the field test research. The field test researches rely on the ANXIN highway old asphalt pavement field hot regeneration project. We got the data about pre and post regenerations asphalt pavement static bending deflection (l0), PFWD dynamic deflection (lp) and PFWD dynamic modulus (EP). The correlation analysis among static bending deflection, PFWD dynamic deflection and PFWD dynamic modulus suggest that PFWD method is a more stable and reliable method than BB method and PFWD method can be a new evaluation technology for the old asphalt pavement field hot regenerations pavement strength.

Abstract: This study has developed a relationship between the Dynamic Modulus (E*) and the Indirect Tensile Strength (ITS) of Hot-Mix Asphalt (HMA) using standard laboratory tests programs. Two types of SuperPave (SP) mixtures were considered namely, SP-III with 15% Reclaimed Asphalt Pavement (RAP) materials and SP-III with 35% RAP materials. Cylindrical samples of 100 mm diameter and 150 mm height were prepared. The samples were then tested for |E*| value at 210C at several loading frequencies following the AASHTO TP 62-07 test protocol. Next, the samples were cut into circular pieces of 38 to 50 mm thickness using laboratory saw. The samples are then tested for ITS value by applying a deformation rate of 50 mm per minute (AASHTO T 283 protocol). The ITS was calculated following the AASHTO T 283-07 test standard. The |E*| values (MPa) of SP-III with 15% RAP at 25, 10, 5.0, 1.0, 0.5, 0.1 Hz are measured to be 65, 59, 52, 34, 31, and 18 times of ITS (psi) respectively. The |E*| values (MPa) of SP-III with 35% RAP at 25, 10, 5.0, 1.0, 0.5, 0.1 Hz are measured to be 41, 38, 33, 24, 20, and 14 times of the ITS (psi) respectively. This study also draws a conclusion that increase in RAP has resulted in increased stiffness and strength.