Analysis of the Dispersion of Viscoelastic Clusters in the Industrial Rotor-Stator Equipment

Materials with complex rheology and viscoelasticity may require special equipment for processing, such as for dispergation. Rheological and mechanical data of the material can help with finding the required equipment or designing equipment. For highly viscous and complex material, a rotor-stator mixer can be a good choice for dispergation. Due to the laminar or creeping mechanism of flow inside the equipment, the dispergation mechanism is assumed to be a combination of the shear stress and slicing of the material by the rotor and stator blades. For the validation of the theory, the mechanical properties of the viscose identified in a previous work were used for comparison with the data from the CFD simulation of the rotor-stator mixer. The comparison showed that the rotor-stator device can overcome the complex shear modulus and ultimate strength of the material and homogenize the solution through a combination of the shear stress and slicing. The theory was also confirmed on the process line proposed for homogenization of the specific material. The stability of viscosity during the process of homogenization was measured and used as the main parameter for quality assessment.

Measurement of complex shear viscosity up to 3 GHz using an electrodeless AT-cut quartz transducer

An experimental method is proposed to determine the frequency-dependent complex shear viscosity of liquids based on the quartz crystal microbalance with dissipation method. An AT-cut quartz transducer without metal electrodes is immersed in a sample liquid and the transducer is electrically coupled to the circuit through the dielectric response of the sample itself. After correcting for the apparent change in the resonance properties due to the dielectric coupling of the sample, our method is able to determine the viscosity of liquids of high polarity and low viscosity at frequencies as high as 3 GHz. The method was then applied to ethylene glycol and the viscoelastic relaxation in the GHz regime was observed. Furthermore, it was also applied to room-temperature ionic liquids to show that the dielectric correction of the resonance properties is valid for conductive liquids.

Characterizing the Diffusion and Rheological Properties of Aged Asphalt Binder Rejuvenated with Bio-Oil Based on Molecular Dynamic Simulations and Laboratory Experimentations

Soybean-derived bio-oil is one of the vegetable-based oils that is gaining the most interest for potential use in the rejuvenation of aged asphalt binders. This laboratory study was conducted to characterize and quantify the diffusion and rheological properties of bio-oil-rejuvenated aged asphalt binder (BRAA) using soybean oil. In the study, the chemical structure of the soybean oil was comparatively characterized using an element analyzer (EA), gel permeation chromatography (GPC), and a Fourier infrared (FTIR) spectrometer, respectively. Based on the chemical structure of the bio-oil, BRAA molecular models were built for computing the diffusion parameters using molecular dynamic simulations. Likewise, a dynamic shear rheometer (DSR) test device was used for measuring and quantifying the rheological properties of the aged asphalt binder rejuvenated with 0%, 1%, 2%, 3%, 4%, and 5% soybean oil, respectively. The laboratory test results indicate that bio-oil could potentially improve the diffusion coefficients and phase angle of the aged asphalt binder. Similarly, the corresponding decrease in the complex shear modulus has a positive effect on the low-temperature properties of BRAA. For a bio-oil dosage 4.0%, the diffusion coefficients of the BRAA components are 1.52 × 10−8, 1.33 × 10−8, 3.47 × 10−8, 4.82 × 10−8 and 3.92 × 10−8, respectively. Similarly, the corresponding reduction in the complex shear modulus from 1.27 × 107 Pa to 4.0 × 105 Pa suggests an improvement in the low-temperature properties of BRAA. Overall, the study contributes to the literature on the potential use of soybean-derived bio-oil as a rejuvenator of aged asphalt binders.

Detection of Reclaimed Asphalt Pavement Presence in Asphalt Mixtures Using a Method of Successive Asphalt Binder Extraction

The work deals with the detection of presence of RAP (reclaimed asphalt pavement) in asphalt mixtures. Information about the presence of RAP in an asphalt layer can be technically advantageous, for example, when planning further recycling of the layer. The method described in the paper can also be used to verify the success of a treatment of an aged binder in RAP, which is dosed in the production of new asphalt mixtures. The asphalt binder was obtained by a method of successive extraction from asphalt mixtures with different RAP content. Basic empirical tests of the asphalt binder (needle penetration and softening point) were chosen to detect the presence of RAP. The complex shear modulus G* was further determined on the extracted binders using a dynamic shear rheometer (DSR).

Evaluation of Rheological Characteristics of Graphite Modified Bitumen

The level of performance of asphalt concrete has a close relationship with the properties of bitumen used. This research evaluates the rheological parameters of graphite modified bitumen. Index properties tests were conducted on bitumen and graphite to determine their suitability. Dynamic viscosity and dynamic shear rheometer were conducted on bituminous binder modified with four different proportion of graphite ranging from 2% to 10% by bitumen weight. Dynamic viscosity test was conducted on bitumen and graphite modified bitumen at temperature of 1350C and 1650C using Brookfield Viscometer. The rheological properties are centered on phase angle (δ) and complex shear modulus (G*) which were determined on bitumen and graphite modified bitumen at temperature ranging from 520C – 700C at 10 rad/s frequency using Dynamic Shear Rheometer in accordance with ASTM D7175-15. The storage modulus (G'), loss modulus (G") and rutting parameters were then evaluated from phase angle and complex shear modulus. The bitumen and graphite modified bitumen showed that graphite modified bitumen has the highest complex shear modulus and rutting parameter of 8984 (kPa) and 33387 (kPa) at 10% graphite content. The results of viscosity helped to determine the mixing and compaction temperatures. Dynamic shear rheometer test results determined the elastic and viscous behaviour at various temperature. The higher the complex shear modulus and rutting parameter the stiffer the binder will resist deformation and rutting.

Study of the Influence of SBS and APDDR on the Low-Temperature Properties of Road Bitumen

A comparative assessment of the effect of two modifiers on the low-temperature properties of BND 90/130 bitumen was investigated using Asphalt Binder Cracking Device (ABCD test) and Dynamic Shear Rheometer (DSR 4-mm test). These modifiers are styrene-butadiene-styrene block copolymer (SBS) and active powder of discretely devulcanized rubber (APDDR) - powder elastomeric modifier obtained by high-temperature shear grinding of waste tire crumb rubber. ABCD results of RTFO-aged samples showed clear and gradual decrease of the ABCD cracking temperature (improvement) for all BC as the modifier concentration increases. It is noteworthy that the Bitumen Composites (modified bitumens) were cracking at higher strain and fracture stress values compared to neat bitumen. Results of DSR-4 mm test showed a decrease in the complex shear modulus (G*), storage modulus (G¢) and loss modulus (G²) BC compared to the neat bitumen. It is shown that bituminous composites have no maximum on the Cole-Cole diagram (dynamic vitrification) at T = -28°C which is observed in the neat bitumen.

Homogeneity and Viscoelastic Behaviour of Bitumen Film in Asphalt Mixtures Containing RAP

This article discusses the phenomenon of fresh and RAP binders miscibility and presents test results of bitumen film properties from specially prepared asphalt mixtures. The miscibility of a fresh binder and a RAP binder still has not been fully recognised. The aim of this study was to determine the homogeneity level of the bitumen film based on viscoelastic assessment. In addition, an attempt was made to assess the impact of fresh binder on the binders blending degree. The study included assessment of homogeneity of bitumen film comprising various types of bituminous binders. The assessment was conducted on the basis of tests in the dynamic shear rheometer regarding rheological properties of the binders recovered from specific layers of the bitumen film using a staged extraction method. A complex shear modulus as a function of temperature, an elastic recovery R and a non-recoverable creep compliance modulus JNR from MSCR test were determined. The conducted statistical analyses confirmed the significant impact of the type of fresh binder on the blending degree. Regressive dependencies have been set between the differences of the complex shear modulus of the binders subject to mixing and differences of the complex shear modulus of binders from the internal and external layer of the bitumen film comprised of those binders. It was found that there is no full blending of fresh hard bitumen-simulated binder from RAP, which results in non-homogeneity of the bitumen film.