Properties Of Aged Asphalt Binders Research Articles

Investigating molecular conformation and packing of oxidized asphaltene molecules in presence of paraffin wax

This study investigates the effect of paraffinic wax (as a base component in many commercial rejuvenators) on the rheological and intermolecular properties of aged asphalt binder. Samples of oxidized asphalt binder doped with (1%, 3%, 5%, and 10%) paraffin wax were characterized using the rotational viscometer (RV), dynamic shear rheometer (DSR), bending beam rheometer (BBR) and direct tension test (DTT). The RV results showed an improvement trend in workability of aged binder as wax content increased. The DSR results (for a temperature range of 10–76 °C) showed lower complex modules for wax-doped specimen than control specimen. The BBR test results performed at sub-zero temperature showed that an increase of wax dosage led to higher creep stiffness modulus indicating that the asphalt binder became generally stiffer in presence of wax at low temperature. However, fracture energy measured through DTT test showed a significant reduction in presence of wax. The latter can be attributed to plausible weak secondary bonds between wax and asphaltene molecules as well as crystallization of wax molecules at low temperature within the asphalt matrix. This in turn can lead to wax crystals playing as stress localization point giving rise to crack nucleation at the wax-asphalt interface reducing overall fracture energy; it was further observed that as the wax content increased, the asphalt binder became more brittle.To further investigate the effect of wax on the molecular conformation and packing in aged asphalt binder, a molecular simulation was performed on a system of wax and oxidized asphaltene. The results of molecular simulations showed a reduction in formation of oxidized asphaltene nano-aggregates as the amount of wax increased in the wax-doped oxidized asphaltene matrix at room temperature, which was also confirmed by size exclusion chromatography. Furthermore, the radial distribution function results showed a less packed structure of oxidized asphaltene molecules in presence of wax molecules. Increasing the wax content also increased the diffusion coefficient of wax into the oxidized asphaltene matrix within a solvent medium. It was also showed that interaction energy of a dimer of oxidized asphaltene is at a lower energy state in presence of wax molecules, which suggests that wax molecules can promote dimerization of oxidized asphaltene molecules while suppressing nano-aggregates formation.

Using a modified asphalt bond strength test to investigate the properties of asphalt binders with poly ethylene wax-based warm mix asphalt additive

This paper presents a feasibility of a modified Asphalt Bond Strength (ABS) test method for use with a new adhesion testing device with three different pullout stubs and its application for evaluating Polyethylene (PE) wax-based Warm Mix Asphalt (WMA) additive. Four different asphalt binders were used to evaluate the feasibility of applying the existing AASHTO ABS test method using a new ASTM-certified adhesion testing device and three different pullout stubs. The modified ABS test method was used to evaluate the loss of adhesion and cohesion in asphalt bond strength due to moisture-induced damage. The paper also discusses rheological properties of extracted asphalt binders from three different test sections in Minnesota, Ohio and Iowa constructed using PE wax-based WMA additive and different amounts of Reclaimed Asphalt Pavement (RAP) materials. Based on the modified ABS test results using the new adhesion testing device, it was found that the proposed pullout stub with 0.0mm thickness (no edge) exhibited consistent results. Based on the results from extracted asphalt performance grading and the multiple stress creep recovery (MSCR) test, it was found that the PE wax-based WMA additive, which was specially designed for asphalt mixtures with a high RAP content, significantly improved the rheological properties of aged asphalt binders from RAP materials.

Use of Rejuvenators to Rejuvenate Asphalt Binders in RAP

With increased demand and limited aggregate and binder supply, hot mix asphalt (HMA) producers discovered that reclaimed asphalt pavement (RAP) is a valuable component in HMA. This paper is concerned with the current issue of higher using RAP (Reclaimed Asphalt Pavement) in asphalt mixtures for pavement wearing courses. It describes the effects of application of three types of rejuvenation additives on properties of aged asphalt binders made from a regular RAP. These rejuvenation additives restore the physical and chemical properties of aged binders. In addition, the aged asphalt binder with rejuvenators applied was subjected to a short-term laboratory aging using the RTFOT (Rolling Thin Film Oven Test). This method simulate aging asphalt binder during the manufacturing process and laying. To assess the binder properties, both the standard empirical tests and more advanced functional tests (dynamic shear rheometer and bending beam rheometer) have been performed. Last part of the paper provides an evaluation of the individual rejuvenation additives. Based on the results it can be concluded that a positive change in properties of aged asphalt binder after applying all the three rejuvenators has been proven.

Properties of Rejuvenated RAPs from Stone Mastic Asphalt

Recycling asphalt pavement creates a cycle of reusing materials that optimizes the use of natural resources. Reclaimed asphalt pavement (RAP) is a useful alternative to virgin materials because it reduces the need to use virgin aggregate. This paper is concerned with the current issue of using RAP in Stone Mastic Asphalt (SMA). SMA is a wearing course, which is especially stable and durable. It describes the effects of application of rejuvenators on properties of asphalt binders. These rejuvenation additives restore the physical and chemical properties of aged binders. In addition, the aged asphalt binder with rejuvenators applied was subjected to a short-term laboratory aging using the RTFOT (Rolling Thin Film Oven Test). To assess the binder properties, both the standard empirical tests and more advanced functional tests (dynamic shear rheometer and bending beam rheometer) have been performed. Last part of the paper provides an evaluation of the individual rejuvenation additives. Based on the results it can be concluded that a positive change in properties of aged asphalt binder obtained from a modified RAP (from SMA) after applying all the rejuvenators has been proven. The effect of the rejuvenators during the manufacturing process and laying has been verified.

Effect of Waste Edible Vegetable Oil on High Temperature Properties of Different Aged Asphalts

Based on the asphalt rejuvenation theory and some related studies, waste cooking oil can be used for asphalt regeneration. The objective of this study is to investigate the high temperature properties of aged asphalt binder with waste edible vegetable oil. The materials used for this study included three sources of virgin asphalt (60-80 grad, 40-60 grad, SBS modified asphalt), three sources of aged asphalt (virgin asphalt aged by RTFOT and PAV), and waste edible vegetable oil with five percentages (3.0, 4.0, 5.0, 6.0, and 7.0% of rejuvenating asphalt). The high temperature characteristics of these rejuvenated asphalts were tested including viscosity and rutting resistance factor (phase angle and complex modulus). The results indicated that three aged asphalt with an appropriate amount of waste edible vegetable oil can respectively achieve the demand of virgin asphalt in rutting resistance factor, phase angle and complex modulus. It means that waste edible vegetable oil could recover high temperature performance of aged asphalt to the level of original asphalt at a certain amount. Moreover, waste edible vegetable oil can slightly reduce the viscosity value of the aged asphalt and thus decrease the mixing and compaction temperature of the mixture.

Investigation of Low Temperature Properties for Ultraviolet Radiation Aged Bitumen and Mixture

Asphalt is an organic mixture with complex compounds and chemical structures which will change after exposed to heat, oxygen, and ultraviolet radiation (UV) and make the physical properties worse, especially at low temperature. In this paper, different aging levels (TFOT，UV-6days) of asphalt binders and mixtures with various mass ratio of layer clay powder to asphalt (0,3%,5%) were considered to investigate the low temperature rheological properties of aged asphalt binders and low temperature strength as well as fatigue properties. Dynamic Shear Rheomoter (DSR) and Universal Testing Machine (UTM) were used to evaluate low temperature properties of bitumen and mixture. From the results, after the addition of layer clay powder, the anti-aging properties is greatly improved and low temperature properties can be better maintained compared to base asphalt.

Rheological characteristics of aged asphalt binder

Different aging levels (RTFOT, PAV-10h, PAV-20h and PAV-30 h) of asphalt binders with various mass ratios of mineral powder to asphalt (0, 0.4, 0.8, 1.2, 1.6, 2.0) were used to investigate the rheological properties of aged asphalt binders with respect to their short and long terms aging characteristics. Viscosity test, dynamic shear test and creep test were conducted. The test results indicate that the viscosity of aged asphalt binder increases sharply with the extension of aging period. Complex shear modulus of aged asphalt increases, which indicates that the stiffness of asphalt binders can increase. The phase angle for aged asphalt binders reduces, which indicates that the elastic portion for viscoelastic property of asphalt binders increases. |G*|·sin δ increases after aging procedure which means that the fatigue resistance becomes poor. The creep test results show that creep strain curves varies remarkably for virgin and aged asphalt binders. The total strain during loading period and the permanent strain decreases significantly for aged asphalt binders, which implies that the elastic portion increases and the viscous portion decreases.