Low Temperature Properties Of Bitumen Research Articles

Low-temperature characterization of bitumen and correlation to chemical properties

A comprehensive understanding of the low-temperature performance of bitumen presents a crucial aspect in the durability of asphalt pavements. In order to capture these properties, current low-temperature testing by the bending beam rheometer (BBR) requires a relatively high amount of aged material, which is not always available. In recent studies, the complex shear modulus and phase angle acquired using a 4 mm geometry with the dynamic shear rheometer (DSR) have been used directly as a criterion for the lower performance grade of bitumen. The purpose of the presented study was to assess the application of the previously developed 4 mm DSR test method for material characterization at low temperatures and to develop a correlation between mechanical and chemical properties. BBR and DSR measurements were performed on 8non-modified and 4 polymer-modified binders. Fourier transform infrared (FTIR) spectroscopy and SARA fractionation were used to gather chemical information about the samples. A strong linear correlation (R2 = 0.93) between the results from BBR and DSR measurements could be observed, allowing an accurate assignment of the low-temperature performance grade for a majority of the investigated samples. Additionally, connections between the FTIR aging index, asphaltene content and the ratio of SARA fractions to the continuous lower performance grade and ΔTc were observed. This demonstrates the potential of chemical analysis methods to provide information about the low-temperature properties of bitumen.

Effect of molecular structure on low-temperature properties of bitumen based on molecular dynamics

Low-temperature cracking is one of the most prevalent distress in asphalt pavement, closely related to the bitumen low-temperature properties. However, the molecular mechanism of low-temperature properties of bitumen is still ambiguous. This paper focuses on studying the effects of molecular structure on the low-temperature properties of bitumen by molecular dynamics (MD) simulation. The low-temperature viscoelasticity and glass transition temperature of bitumen were measured by dynamic shear rheometer (DSR) and differential scanning calorimeter (DSC) experiment. The MD models containing 20 kinds of molecules were constructed to represent the bitumen and validated by density, shear modulus and glass transition temperature. Furthermore, the effects of molecular structure on the low-temperature properties were analyzed by relative density, mean square displacement (MSD), radial distribution function (RDF), and potential energy. The DSR and DSC results showed that the low-temperature properties ranking of the bitumen is HY90 > LH50 > LH90 > LH70. The relative density and RDF curves showed that the increasing aromatic carbons in resins and aromatics reduce the asphaltenes aggregation degree and improve the low-temperature properties by promoting the formation and dispersion of asphaltene-resin aggregates. The MSD curves indicated that the bitumen with a high average diffusion coefficient has good low-temperature properties. The increase of aromatic carbons improves the diffusion coefficient by forming molecules with low molecular mass. Moreover, non-bond energy positively correlates with the low-temperature properties of bitumen. The low-temperature properties of bitumen can be optimized by increasing the resins and aromatics, or adding molecules with high aromatic carbon content and diffusion coefficients.

Characterizing mechanical response of bio-modified bitumen at sub zero temperatures

Cracks associated with large temperature fluctuation especially in cold regions are among prevalent pavement distresses. Binder rheology is typically found to the key factor affecting low temperature cracking resistance. Recognizing the importance of binder properties, many road authorities are requiring the use of special additives to enhance low temperature properties of binder to alleviate low temperature cracking problems. However, most of these modifiers are petroleum-based products with unstable price and depleting resources. Therefore, the asphalt industry is looking for renewable alternatives for modifying bitumen and improving its low temperature performance. Accordingly, this paper incorporates laboratory experiments and modeling to study merits of modifying bitumen with several bio-binders to enhance low temperature properties of bitumen. To investigate rheological properties at low temperatures, an extended bending beam rheometer test was used incorporating a simple fractional viscoelastic model based on the general power law. The data collected during loading and unloading portion of the test was used to evaluate the effect of introduction of bio-modifiers on low temperature properties of bitumen. The experimental results showed that introduction of bio-modifiers to bitumen significantly enhanced bitumen behavior both during creep loading and relaxation. The results of finite element modeling based on the extended bending beam rheometer geometry and boundary conditions proved that the simple fractional viscoelastic model can accurately characterize low-temperature mechanical behavior of bio-modified bitumen.

High- and Low-Temperature Properties of Layered Silicate-Modified Bitumens: View from the Nature of Pristine Layered Silicate

Layered silicates, as bitumen modifiers, have received increasing attention. The main objective of this study was to evaluate the influence of layered silicates on bitumen properties. For this study, montmorillonite (MMT), rectorite (REC), organic montmorillonite (OMMT), and organic rectorite (OREC) were selected. The layered structure type of layered silicates was characterized by SEM (scanning electron microscope) and XRD (X-ray diffraction diffractometer). Tests for determining high-temperature properties included viscosity, DSR (dynamic shear rheometer), and TG (thermogravimetry) tests, and studies for determining the low-temperature properties were conducted by BBR (bending beam rheometer) and DSC (differential scanning calorimetry) tests. Our results show that MMT, REC, OMMT, and OREC were all intercalated structures. OREC had the largest d001 interlayer space, followed by REC, OMMT, and MMT. OREC improved the high-temperature property of virgin bitumen more effectively than OMMT. Meanwhile, REC-modified bitumen exhibited a high-temperature property similar to OMMT-modified bitumen. When compared with REC and OREC, MMT and OMMT were less efficient in reducing the low-temperature properties of virgin bitumen, and OMMT was the least efficient. Therefore, it can be concluded that the nature of pristine layered silicates has a great impact on the high- and low-temperature properties of bitumen. Moreover, organic treatment can simultaneously improve the high- and low-temperature properties of layered silicate-modified bitumens.

Effect of Carbon Black on the High and Low Temperature Properties of Bitumen

In the present study, the effect of carbon black (CB) as an additive on resistance of bitumen to delay or prevent rutting and low temperature cracking was investigated. For this purpose, different amounts of CB (0, 5, 10, and 15 wt%) were added into bitumen with PG 58-28. Conventional tests (penetration, softening point, Fraass breaking point, ductility, and kinematic viscosity) and Superpave binder tests (rotational viscosity, dynamic shear rheometer, and bending beam rheometer test) were carried out to determine the physical and rheological properties of pure and modified bitumens. In addition, high and low temperature performance grades of pure and modified bitumens were identified according to Superpave binder specification. The results indicated that the addition of CB increased the stiffness and resistance of bitumen to rutting at high temperatures and resistance to thermal cracking at low temperatures of bitumen. Finally, the bitumen becomes more elastic and less susceptible to temperature changes.

Effect of Silane Coupling Agent Surface Modified Layered Double Hydroxides on Properties of Bitumen

Layered double hydroxides (LDHs) surface modified by silane coupling agent KH550 were prepared to modify bitumen, the surface modified LDHs (KH550-LDHs) were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD). The effect of KH550-LDHs and LDHs on physical and anti-ageing properties of bitumen was evaluated by means of physical test. The results of FTIR showed that KH550 had successfully grafts onto the surface of LDHs, and XRD result showed that KH550 had little effect on the crystal structure of LDHs. The storage stability test showed that KH550-LDHs dispersed better homogeneously and existed more stable than LDHs in bitumen. The physical properties tests indicated that high and low temperature properties of bitumen were improved compared with LDHs. After UV aging with the addition of KH550-LDHs, the increase rate of softening point slowed remarkably, the reduction rate of ductility declined evidently compared with LDHs. Aging indices (softening point increment and ductility retention rate) show that KH550-LDHs exhibited better improvement than LDHs in UV aging resistance of bitumen, implying more effective modification of KH550-LDHs which is due to the enhanced compatibility between KH550-LDHs and bitumen.

Low temperature characterization of bituminous binders with a new cyclic shear cooling (CSC) failure test

Low temperature cracking of asphalt pavements is associated to the thermal stresses created when asphalt binder changes from a ductile into a brittle state during cooling. Under repetitive traffic loads, this change of properties can become a significant problem, resulting in the formations of large cracks on the driving surface, thus requiring early pavement repair. Nevertheless, the conventional test methods for assessing low temperature properties of bitumen are often insufficient and subject to low reproducibility. Therefore, a reliable method is necessary to characterize the performance of bituminous binders at low temperature. This work presents the cyclic shear cooling failure test (CSC-failure test) as an alternative method based on a failure test with the dynamic shear rheometer (DSR) at decreasing temperature until fracture occurs. Operational parameters, like shear strain amplitude or loading frequency, have been analysed in order to develop a reproducible procedure applicable for different types of bituminous binders. Moreover, a failure criterion has been defined by analysing the different characteristic temperatures from the failure curves obtained in the test.

Effect of Gamma-Irradiated Recycled Low-Density Polyethylene on the High- and Low-Temperature Properties of Bitumen

This paper describes polymer modification of bitumen with gamma-irradiated recycled (γ-LDPER) low-density polyethylene. The recycled low-density polyethylene (LDPER) was obtained from greenhouse films exposed to sunlight at least one year. The surface of theLDPERwas treated by gamma beam irradiation that provided formation of free radicals and some functional groups that may contribute to the creation of strong chemical bonds between polymer modifier and bitumen. Five different samples of bitumen/γ-LDPERcompositions with the modifier content, wt. %: 1, 3, 5, 7 and 9, were prepared. The effects of theγ-LDPERon original and aged bitumen were investigated by means of morphological, chemical, and physical testing program, including FTIR spectroscopy, conventional tests, rotational viscosity (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR) tests. Superior performing asphalt pavements (Superpave) specifications were used to analyze mechanical test results as well as to determine the performance grades (PG) of the binders. Optimum usage of theγ-LDPERas modifier in bitumen were suggested after testing program. The results reveal the stiffening effect of theγ-LDPERon bitumen that provide enhanced temperature susceptibility and also promise better performance grades (PG) withγ-LDPERpolymer modification.

Influence of Physical Hardening on the Low-Temperature Properties of Bitumen and Asphalt Mixtures

A laboratory study was carried on the effects of physical hardening on the low-temperature performance of bitumen and corresponding asphalt mixtures. Bitumen testing involved measurements of glass transition temperature and creep stiffness at various isothermal storage times. Mixture testing included evaluation of glass transition temperature, thermal stress build-up in restrained conditions and thermal strains in non-restrained conditions. A physical hardening rate was introduced both for bitumen and mixtures (PHRB and PHRM). Results indicated that glass transition temperatures can be reduced passing from bitumen to mixtures and a correlation can be found between the hardening rates PHRB and PHRM.

Rheological properties for aged bitumen containing ultraviolate light resistant materials

Aging, which occurs in asphalt roadway pavements during construction and service life, can affect the rheological properties of bitumen. Different aging levels (TFOT and ultraviolate aging (UV aging for short) for 6days) of bitumen with various mass ratios of the ultraviolate light resistant materials to bitumen were considered to investigate in this paper. LDHS were used as the ultraviolate light resistant materials. The TFOT tests and UV aging process were used to simulate short-term field thermal-oxidative aging and long-term field light-oxygen aging of bitumen separately. Basic properties test, dynamic shear temperature sweep and frequency sweep tests as well as creep test were conducted in this paper. Dynamic Shear Rheomoter (DSR) was also used to evaluate low temperature properties of bitumen. The results showed that LDHS can improve the UV aging resistance of the bitumen, and the bitumen with more LDHS can present a better low-temperature performance compared to the base bitumen.

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.