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.

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.

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.

Study on aging of lignin modified asphalt under thermogravimetric conditions

In order to study the aging process of lignin-modified asphalt and explore the effect of lignin on the anti-aging performance of base asphalt, 4 sets of lignin-modified asphalt were prepared under different base asphalt, different dosage, temperature and time. Based on the thermal oxidation test (TFOT), dynamic shear rheological test (DSR), thermogravimetric test (TG), and infrared spectroscopy micro-performance test (FTIR), the high-temperature rheological properties and performance of aging lignin-based asphalt with different content were investigated. The changing law of the chemical properties of functional groups. The results show that the addition of lignin to the base asphalt sample increases the complex shear modulus G* and decreases the phase angle δ compared to the base asphalt sample prepared by the same sample preparation process. In the same sample, with the continuous increase of the test temperature, the complex shear modulus G* of the matrix asphalt before or after aging and the modified asphalt with different content of lignin showed a downward trend. The modification mechanism of lignin on asphalt is essentially that lignin decomposes and reacts with oxygen in the process of thermal oxidative aging, which delays the oxidation reaction of asphalt during aging, so as to achieve the anti-aging effect of asphalt.

The properties of nano-CaCO3/nano-ZnO/SBR composite-modified asphalt

To solve the problem of the pavement being aged due to the influence of temperature, light and other environmental factors are brought in service. Nano-CaCO3 surface was activated by 6% KH-550, and nano-ZnO surface was activated by 6% aluminate. Nano-CaCO3/nano-ZnO/SBR composite-modified asphalt was prepared. The optimum proportion of composite-modified asphalt was determined by orthogonal test. The influence of modifiers on asphalt pavement performance was comprehensively studied. The microstructure of composite-modified asphalt was characterized by scanning electron microscopy and infrared spectroscopy. The mechanism of composite-modified asphalt was analyzed. The results show that the optimum combination of composite-modified asphalt is 4% nano-CaCO3 + 5% nano-ZnO + 4% SBR, the aging performance of the composite-modified asphalt is reduced by 6.9%, and the viscosity is increased by 14.6–23.1%. The complex shear modulus is increased by 24.1% at 82°C, the stiffness modulus is decreased, on average, by 21.1%. and the creep curve slope is increased by 9% on average. In the meantime, during the preparation process of composite-modified asphalt, it mainly occurred due to chemical reaction with surface-modified nanomaterials and physical change with SBR polymer materials.

Artificial Intelligence Prediction of Rutting and Fatigue Parameters in Modified Asphalt Binders

The complex shear modulus (G*) and phase angle (δ) are fundamental viscoelastic rheological properties used in the estimation of rutting and fatigue pavement distress in asphalt binder. In the tropical regions, rutting and fatigue cracking are major pavement distress affecting the serviceability of road infrastructure. Laboratory testing of the complex shear modulus and phase angle requires expensive and advanced equipment that is not obtainable in major laboratories within the developing countries of the region, giving rise to the need for an accurate predictive model to support quality pavement design. This research aims at developing a predictive model for the estimation of rutting and fatigue susceptive of asphalt binder at intermediate and high pavement temperatures. Asphalt rheological and ageing test was conducted on eight mixes of modified binders used to build the study database containing 1976 and 1668 data points for rutting and fatigue parameters respectively. The database was divided into training and simulation dataset. The Gaussian process regression (GPR) algorithm was used to predict the rutting and fatigue parameters using unaged and aged conditioned inputs. The proposed GPR was compared with the support vector machine (SVM), recurrent neural networks (RNN) and artificial neural network (ANN) models. Results show that the model performed better in the estimation of rutting parameter than the fatigue parameter. Further, unaged input variables show better reliability in the prediction of fatigue parameter.