Low Temperature Properties Of Asphalt Mixtures Research Articles

Effect of aging on the low-temperature performance of fiber-reinforced asphalt mixtures

To study the effect of aging on the low-temperature crack resistance of fiber asphalt mixes, three kinds of fibers (lignin fiber, polyester fiber, and basalt fiber) were dry blended into AC-13 asphalt mixes to prepare unaged, asphalt aged (that is, the original asphalt material is subjected to aging treatment), short-term aged, and long-term aged fiber reinforced asphalt mixes. Semicircular bending (SCB) tests and scanning electron microscopy tests were used to analyze and study the effects of aging time and fiber type on the low-temperature properties of asphalt mixtures at an ambient temperature of −5 °C. The SCB test results indicated that: with the deepening of aging, the fracture toughness and fracture energy of the fiber asphalt mixture specimens will tend to decrease, and the aging of the original asphalt has a greater impact on the specimens without fiber; there was great variability in the effect of lignin fibers on the crack resistance of the mix, but it could be a good promoter in unaged asphalt mixes; polyester fiber is the material of choice for improving low-temperature crack resistance in long-term aging pavements; the incorporation of basalt fiber greatly enhances the crack resistance of asphalt mixes and is an excellent material for improving aging asphalt mixes. It is clearly seen by the scanning electron microscope test that with the deepening of aging, the adhesion of asphalt and aggregate gradually deteriorates, and even more so, there is the phenomenon of fine aggregate flaking, and the fiber cannot play an excellent role in reinforcement and crack resistance.

Effect of gradation segregation on low-temperature crack resistance of asphalt pavement using 3D DEM

Gradation segregation can have a great influence on the low-temperature crack resistance of asphalt pavement. In this paper, five kinds of AC-20 asphalt mixtures with different degrees of gradation segregation are designed according to the standards put forward by the American NCHRPRReport-441 project report, and numerical models are developed using the DEM to simulate the splitting test. The effect of gradation segregation is analyzed on the low-temperature crack resistance of asphalt pavement from two aspects of macroscopic (mean splitting strength and horizontal tensile stress) and mesoscopic (contact force, displacement and crack). The results show that in the macro level, the coarse aggregate gradation segregation leads to the decrease of the splitting strength and horizontal tensile stress of the mixture, while the fine aggregate gradation segregation leads to the increase of the splitting strength and horizontal tensile stress of the mixture. Moreover, in the meso-level, the coarse aggregate gradation segregation leads to the decrease of the internal contact force, the displacement and the number of cracks, and the fine aggregate gradation segregation leads to the increase of the internal contact force and quantity of the mixture. Furthermore, the macroscopic response caused by segregation is related to the mesoscopic response and coarse aggregate heavy segregation has the greatest influence on macro and meso mechanical parameters and the low-temperature properties of asphalt mixtures. The research results provide a new idea and way to evaluate the low-temperature crack resistance of asphalt pavement based on the meso-level gradation segregation.

Assessment of Thermal Stresses in Asphalt Mixtures at Low Temperatures Using the Tensile Creep Test and the Bending Beam Creep Test

Thermal stresses are leading factors that influence low-temperature cracking behavior of asphalt pavements. During winter, when the temperature drops to significantly low values, tensile thermal stresses develop as a result of pavement contraction. Creep test methods can be suitable for the assessment of low-temperature properties of asphalt mixtures. To evaluate the influence of creep test methods on the obtained low-temperature properties of asphalt mixtures, three point bending and uniaxial tensile creep tests were applied and the master curves of stiffness modulus were analyzed. On the basis of creep test results, rheological parameters describing elastic and viscous properties of the asphalt mixtures were determined. Thermal stresses were calculated and compared to the tensile strength of the material to obtain the failure temperature of the analyzed asphalt mixtures. It was noted that lower strain values of creep curves were obtained for the Tensile Creep Test (TCT) than for the Bending Beam Creep Test (BBCT), especially at lower temperatures. Results of thermal stress calculations indicated that higher reliability was obtained for the viscoelastic Monismith method based on the TCT results than for the simple quasi-elastic solution of Hills and Brien. The highest agreement with the TSRST results was also obtained for the Monismith method based on the TCT results. No clear relationships were noted between the predicted failure temperature and different methods of thermal stress calculations.

Influence of cooling rate and additives on low-temperature properties of asphalt mixtures in the TSRST

The paper presents the results and analysis of low-temperature properties of asphalt mixtures according to Thermal Stress Restrained Specimen Test (TSRST) and Indirect Tensile Test methods. Different groups of bitumen were investigated: neat, SBS-modified and highly SBS-modified. Influence of cooling rates (1 °C/h, 3 °C/h, 5 °C/h and 10 °C/h) and additives (aramid fibres and crumb rubber) was identified as well. Moreover, for each factor stiffness moduli were back-calculated from the TSRST results and analysed. The greatest impact on the TSRST results had type of bitumen, followed by the cooling rate and additives. Application of longer fibres improved low-temperature properties of the asphalt mixtures.

Comparison of low-temperature fracture and strength properties of asphalt mixture obtained from IDT and SCB under different testing configurations

This paper presents an investigation on the low-temperature properties of asphalt mixture determined with the indirect tensile (IDT) and the semi-circular bending (SCB) experimental methods. First, IDT and notched and unnotched SCB tests are performed on a set of ten different asphalt mixtures. Then, the maximum stress (strength) along the crack surface of SCB specimens is estimated using a commercial finite-element software and cohesive zone modelling. Finally, a set of simple linear relations between the numerically determined SCB strength on notched specimens and the nominal strength value experimentally measured on IDT specimens is derived. It is found that the newly proposed relationship can be potentially used to predict the asphalt mixtures’ nominal strength of IDT specimens based on SCB notched fracture tests. No good correlation could be found between SCB strength on unnotched specimens and the corresponding IDT measurements at this stage. This is most likely due to the simple FEM approach selected and the different failure mechanisms of the SCB unnotched configuration.

Low-temperature performance of recycled asphalt mixtures under static and oscillatory loading

In this paper the effect of reclaimed asphalt pavement (RAP) on the low-temperature properties of asphalt mixture is experimentally investigated and modelled. Two test methods are used: bending beam rheometer (BBR) mixture creep test, which is based on static loading, and dynamic shear rheometer (DSR) mixture complex modulus test, which uses oscillatory loading. First, creep stiffness, m-value, thermal stress, critical cracking temperature and complex modulus are derived, and then, statistically and graphically compared. Then, the rheological Huet model is used to evaluate the experimental BBR measurements and to derive a simple relationship associating the characteristic time of mixtures to the RAP content. The statistical results indicate that most of the mixtures prepared with RAP have relatively poorer performance compared to virgin mixtures up to a RAP content of 25%. Based on rheological modelling, it appears that RAP and characteristic time are linked through an exponential relationship.

Effect of Aging on the Low-Temperature Properties of Asphalt Mixture

This article studies the low-temperature anti-cracking properties of plain asphalt mixtures and rubber-modified asphalt mixtures at different aging condition. Laboratory flexural test was conducted on the beam specimens of plain asphalt mixtures and rubber-modified asphalt mixtures. Experiment results indicate that rubber-modified asphalt mixtures have superior low-temperature anti-cracking performance than that of plain asphalt mixtures. Compared with the short term oven aging test, the long term oven aging test has more significant effect on the low-temperature anti-cracking of the mixture. In order to better represent the low-temperature anti-cracking of in-service aging asphalt pavement, the long term oven aging test should be used to appraise the low-temperature anti-cracking of asphalt pavements in china.

Asphalt Mixture Beams Used in Bending Beam Rheometer for Quality Control

This paper introduces the use of asphalt mixture beams in the bending beam rheometer (BBR) for quality control with a project in Utah as a case study. A good solution for quality control, the BBR test can be performed by materials laboratory staff at highway agencies and private materials laboratories because it is reasonably priced, is rugged-tested, uses limited material, is conditioned quickly, is available, and is familiar to staff at materials laboratories for everyday mix design and quality control. The paper begins with a literature review of past research work in support of using BBR tests to measure properties of asphalt mixture beams. An asphalt construction project in Utah was selected to demonstrate the applicability of using asphalt mixture beams in the BBR for quality control. Field samples obtained from the project in Utah were shipped to the laboratory, where comparisons of low-temperature properties of asphalt mixtures were done with the BBR. Results easily showed an anomaly on two paving days, when the m value (slope of the curve) was higher than normal. Because of this irregularity, further testing was initiated with the indirect tension test performed at the Asphalt Institute; the test confirmed the results from the BBR. On the basis of results and demonstration, it is clear that using asphalt mixture beams in the BBR is feasible for quality control to evaluate the performance of constructed materials. The application of using asphalt mixture beams in the BBR can be easily adopted by highway agencies to facilitate quality control operations in asphalt construction.