Sandra Erkens - Academia.edu (original) (raw)
Papers by Sandra Erkens
7th RILEM International Conference on Cracking in Pavements, 2012
Most design methods for pavements use a factor explaining the difference between pavement life pr... more Most design methods for pavements use a factor explaining the difference between pavement life predictions from design models and performance in the road [1]. Part of this correction factor is healing, the natural capacity of asphalt concrete to recover in rest periods, which generally are not present in laboratory fatigue tests in order to limit the test time. In the design method used for Dutch highways [2] a shift factor of 4 is traditionally used. This factor is based on in-practice behaviour of pavements with mixes using straight run bitumen of limited softness (mostly 40/60 and 70/100 pen bitumen). Currently many developments regarding polymer and chemical modification and the use of hard binders raise questions about the value of the shift factor for these mixtures as well as questions about how much of this factor is actually related to the healing potential of the mixes. In the project described in this paper it is investigated whether the four point bending test used to assess the fatigue resistance in the European standard can be used in a discontinuous way to determine the healing capacity of a mix. In order to do this, a set of continuous and discontinuous tests was performed on two mixes that deviate only in the softness of their binder, 70/100 or 10/20. Although the approach appears promising in its simplicity and the consistency of the results, finding the correct interpretation remains difficult and may require linking the pragmatic with more fundamental understanding of the mechanism behind healing.
Construction and Building Materials
Journal of Transportation Engineering, Part B: Pavements
Journal of Materials in Civil Engineering
Transportation Research Record: Journal of the Transportation Research Board
Micromechanics, which can be used to relate the properties of a composite to the properties of in... more Micromechanics, which can be used to relate the properties of a composite to the properties of individual constituents, is considered a good approach to understanding the fundamental mechanisms behind the behavior of asphalt materials. Compared with the semi-empirical and numerical micromechanical models, analytical micromechanical models do not need calibration factors. In addition, they can provide analytical solutions on the basis of a series of assumptions. Using these models, researchers have separated the effects of different stiffening mechanisms (i.e., the volume-filling reinforcement, the physicochemical reinforcement, and the particle-contact reinforcement) for mastic. However, similar research work has not been conducted for asphalt mixtures and, moreover, the characteristics of the particle-contact reinforcement have not been deeply analyzed by researchers. Therefore, this paper aims to understand the stiffness of asphalt mixture through micromechanics. The focus of this...
Construction and Building Materials
Progress in Rubber, Plastics and Recycling Technology
Considering the application scenarios of rubber granules from waste tires in the bitumen modifica... more Considering the application scenarios of rubber granules from waste tires in the bitumen modification process (wet or dry process), both aerobic and anaerobic aging of rubber may occur. The current study aims to investigate the thermal aging behavior of waste tire rubber samples using nanoindentation and environment scanning electron microscopy (ESEM) tests. Both aerobic and anaerobic aging tests with different durations were conducted on rubber samples. The complex moduli of aged rubber samples were measured by nanoindentation tests. The surface morphology and elemental composition of aged samples were obtained by ESEM tests together with the energy dispersive X-ray analysis. Results have shown that for both aerobic and anaerobic aging, the equilibrium modulus derived from the complex modulus curve first increases and then decreases with aging time. However, the time needed for the aerobically aged sample to reach the maximum equilibrium modulus is shorter than the anaerobic case. ...
Construction and Building Materials
Transportation Research Record: Journal of the Transportation Research Board
Rubber swelling in bitumen, which is a diffusion-induced volume expansion process, plays a domina... more Rubber swelling in bitumen, which is a diffusion-induced volume expansion process, plays a dominant role in the design of crumb rubber modified bitumen binders and their properties development. This study aims to investigate the kinetics of bitumen diffusion into truck tire rubber, the equilibrium swelling characteristics of rubber, and the mechanical properties of rubber before and after swelling at different high temperatures. Fourier transform infrared spectroscopy results indicate that no rubber dissolution happens during the interaction in the temperature range from 160°C to 200°C. Aliphatic compounds from bitumen preferentially diffused into rubber during the swelling process. The diffusion coefficients of bitumen into rubber were determined by the sorption test using the gravimetric method. The diffusion coefficient increases with the increase of temperature in an Arrhenius form. The volume expansion of rubber during swelling was captured by the X-ray computed tomography scan...
Construction and Building Materials
Materials and Structures
In-depth understanding of the synergetic effect between the various incorporating constituents in... more In-depth understanding of the synergetic effect between the various incorporating constituents in asphalt binders (e.g., polymers, fillers) is needed to design durable paving materials with desired properties. In this research, the focus was first on the effect of the reactivity of fillers on the evolution of adhesive strength between stone aggregates and epoxy modified asphalt mastics during the epoxy polymerization. Uniaxial tensile tests were performed on different combinations of fillers and binders with and without the epoxy-based polymer, and at different modification levels. Based on the results of the tensile tests, the increase of the adhesive strength of mastic with aggregates was generally lower when reactive filler particles (i.e., hydrated lime) were added than of epoxy binders with non-reactive filler. In other words, the non-reactive fillers did not influence the adhesion process and were thus selected for the next step studies on aging. The chemo-mechanical changes o...
Construction and Building Materials
Construction and Building Materials
International Journal of Pavement Engineering
Oxidative aging is responsible for the irreversible asphalt stiffening and embrittlement leading ... more Oxidative aging is responsible for the irreversible asphalt stiffening and embrittlement leading to asphalt pavements of increased susceptibility to fatigue and thermal cracking. In recent years, various flexible binders have been introduced in asphalt industry to produce long-life pavements and the epoxy asphalt binders are among them. Nevertheless, in-depth understanding of the oxidative aging mechanism of epoxy asphalt binders and binding systems is still needed to enable reliable predictions of material degradation through service life. In this research, the compositional and rheological changes of epoxy asphalt, with and without filler, were analysed by means of Fourier Transform Infrared spectroscopy and Dynamic Shear Rheometer. Especially, kinetics (Arrhenius) parameters of epoxy asphalt have been determined by tracking the chemical composition changes. Oxidation of carbon species in epoxy asphalt is compositional dependent, and low values of activation energy accompany in low values of reaction rate are shown by adding epoxy in asphalt. Furthermore, the epoxy asphalt mastics (binders with filler) have been subjected to rheological testing to evaluate the stiffening effect as oxidation proceeds. Increase of modulus over a wide range of frequencies, decrease of frequency dependency of modulus of epoxy asphalt and shifting of phase angle to lower values are some important observations noticed as well. Overall, oxidation in epoxy asphalt materials occurs slowly yielding to oxygen-resistant binders when epoxy compounds are incorporated in asphalt binders.
Molecules
Organosolv lignin, a natural polymer, has been used in this study as an oxidation inhibitor in bi... more Organosolv lignin, a natural polymer, has been used in this study as an oxidation inhibitor in bitumen. Particularly, the effect of oxidative aging on the chemical compositional changes and on the rheology of bituminous binders with organosolv lignin and the impact to inhibit oxidation in bitumen were evaluated. Firstly, after analyzing the microstructure and surface characteristics of utilized organosolv lignin, a high shear mixing procedure was followed to produce binders of different proportions of lignin in bitumen. Pressure aging vessel conditioning was applied to these binders to simulate in-field aging and a series of tests were performed. Fourier transform infrared spectroscopy was used to track the compositional changes of lignin–bitumen systems before and after aging respectively. The rheological changes due to oxidative aging in the different lignin–bitumen systems were studied by means of dynamic shear rheometer tests. Based on the spectroscopic laboratory analyses, cert...
Construction and Building Materials
h i g h l i g h t s Epoxy asphalt mixes have higher tensile strength than conventional asphalt mi... more h i g h l i g h t s Epoxy asphalt mixes have higher tensile strength than conventional asphalt mixes. The four-point bending tests indicate that a high modulus material, as the epoxy asphalt, can effectively reduce deflections of specimen beams and improve their fatigue resistance. Epoxy-type tack coat improves significantly the bonding strength between two asphaltic layers. Two-layer monolithic pavements with epoxy asphalt could mitigate bonding defects of surfacing layers of enhanced strength, modulus and fatigue resistance.
Materials
This Special Issue “Sustainable Designed Pavement Materials” has been proposed and organized as a... more This Special Issue “Sustainable Designed Pavement Materials” has been proposed and organized as a means to present recent developments in the field of environmentally-friendly designed pavement materials. For this reason, articles included in this special issue relate to different aspects of pavement materials, from industry solid waste recycling to pavement materials recycling, from pavement materials modification to asphalt performance characterization, from pavement defect detection to pavement maintenance, and from asphalt pavement to cement concrete pavement, as highlighted in this editorial.
International Journal of Pavement Engineering
Waste tire rubber has been incorporated into asphalt modification for decades due to its various ... more Waste tire rubber has been incorporated into asphalt modification for decades due to its various benefits. There are two main mechanisms during bitumen-rubber interaction: rubber swelling and chemical degradation. This study surveys these two processes from the viewpoint of polymer science. The kinetics of rubber dissolution and thermodynamics of rubber swelling are discussed to provide a fundamental understanding of the interaction process and to demonstrate how optimisation of material selection and processing procedures can lead to the desired binder properties. Factors including the interaction conditions and raw material characteristics are analysed based on the previous theories and compared with experimental results.
Construction and Building Materials
h i g h l i g h t s A robust methodology was developed to evaluate the storage stability of CRMB ... more h i g h l i g h t s A robust methodology was developed to evaluate the storage stability of CRMB binders. The instability mechanism was explored by the concept of dynamic asymmetry. It is possible to manipulate raw material properties and interaction conditions to achieve a storage-stable CRMB blend.
7th RILEM International Conference on Cracking in Pavements, 2012
Most design methods for pavements use a factor explaining the difference between pavement life pr... more Most design methods for pavements use a factor explaining the difference between pavement life predictions from design models and performance in the road [1]. Part of this correction factor is healing, the natural capacity of asphalt concrete to recover in rest periods, which generally are not present in laboratory fatigue tests in order to limit the test time. In the design method used for Dutch highways [2] a shift factor of 4 is traditionally used. This factor is based on in-practice behaviour of pavements with mixes using straight run bitumen of limited softness (mostly 40/60 and 70/100 pen bitumen). Currently many developments regarding polymer and chemical modification and the use of hard binders raise questions about the value of the shift factor for these mixtures as well as questions about how much of this factor is actually related to the healing potential of the mixes. In the project described in this paper it is investigated whether the four point bending test used to assess the fatigue resistance in the European standard can be used in a discontinuous way to determine the healing capacity of a mix. In order to do this, a set of continuous and discontinuous tests was performed on two mixes that deviate only in the softness of their binder, 70/100 or 10/20. Although the approach appears promising in its simplicity and the consistency of the results, finding the correct interpretation remains difficult and may require linking the pragmatic with more fundamental understanding of the mechanism behind healing.
Construction and Building Materials
Journal of Transportation Engineering, Part B: Pavements
Journal of Materials in Civil Engineering
Transportation Research Record: Journal of the Transportation Research Board
Micromechanics, which can be used to relate the properties of a composite to the properties of in... more Micromechanics, which can be used to relate the properties of a composite to the properties of individual constituents, is considered a good approach to understanding the fundamental mechanisms behind the behavior of asphalt materials. Compared with the semi-empirical and numerical micromechanical models, analytical micromechanical models do not need calibration factors. In addition, they can provide analytical solutions on the basis of a series of assumptions. Using these models, researchers have separated the effects of different stiffening mechanisms (i.e., the volume-filling reinforcement, the physicochemical reinforcement, and the particle-contact reinforcement) for mastic. However, similar research work has not been conducted for asphalt mixtures and, moreover, the characteristics of the particle-contact reinforcement have not been deeply analyzed by researchers. Therefore, this paper aims to understand the stiffness of asphalt mixture through micromechanics. The focus of this...
Construction and Building Materials
Progress in Rubber, Plastics and Recycling Technology
Considering the application scenarios of rubber granules from waste tires in the bitumen modifica... more Considering the application scenarios of rubber granules from waste tires in the bitumen modification process (wet or dry process), both aerobic and anaerobic aging of rubber may occur. The current study aims to investigate the thermal aging behavior of waste tire rubber samples using nanoindentation and environment scanning electron microscopy (ESEM) tests. Both aerobic and anaerobic aging tests with different durations were conducted on rubber samples. The complex moduli of aged rubber samples were measured by nanoindentation tests. The surface morphology and elemental composition of aged samples were obtained by ESEM tests together with the energy dispersive X-ray analysis. Results have shown that for both aerobic and anaerobic aging, the equilibrium modulus derived from the complex modulus curve first increases and then decreases with aging time. However, the time needed for the aerobically aged sample to reach the maximum equilibrium modulus is shorter than the anaerobic case. ...
Construction and Building Materials
Transportation Research Record: Journal of the Transportation Research Board
Rubber swelling in bitumen, which is a diffusion-induced volume expansion process, plays a domina... more Rubber swelling in bitumen, which is a diffusion-induced volume expansion process, plays a dominant role in the design of crumb rubber modified bitumen binders and their properties development. This study aims to investigate the kinetics of bitumen diffusion into truck tire rubber, the equilibrium swelling characteristics of rubber, and the mechanical properties of rubber before and after swelling at different high temperatures. Fourier transform infrared spectroscopy results indicate that no rubber dissolution happens during the interaction in the temperature range from 160°C to 200°C. Aliphatic compounds from bitumen preferentially diffused into rubber during the swelling process. The diffusion coefficients of bitumen into rubber were determined by the sorption test using the gravimetric method. The diffusion coefficient increases with the increase of temperature in an Arrhenius form. The volume expansion of rubber during swelling was captured by the X-ray computed tomography scan...
Construction and Building Materials
Materials and Structures
In-depth understanding of the synergetic effect between the various incorporating constituents in... more In-depth understanding of the synergetic effect between the various incorporating constituents in asphalt binders (e.g., polymers, fillers) is needed to design durable paving materials with desired properties. In this research, the focus was first on the effect of the reactivity of fillers on the evolution of adhesive strength between stone aggregates and epoxy modified asphalt mastics during the epoxy polymerization. Uniaxial tensile tests were performed on different combinations of fillers and binders with and without the epoxy-based polymer, and at different modification levels. Based on the results of the tensile tests, the increase of the adhesive strength of mastic with aggregates was generally lower when reactive filler particles (i.e., hydrated lime) were added than of epoxy binders with non-reactive filler. In other words, the non-reactive fillers did not influence the adhesion process and were thus selected for the next step studies on aging. The chemo-mechanical changes o...
Construction and Building Materials
Construction and Building Materials
International Journal of Pavement Engineering
Oxidative aging is responsible for the irreversible asphalt stiffening and embrittlement leading ... more Oxidative aging is responsible for the irreversible asphalt stiffening and embrittlement leading to asphalt pavements of increased susceptibility to fatigue and thermal cracking. In recent years, various flexible binders have been introduced in asphalt industry to produce long-life pavements and the epoxy asphalt binders are among them. Nevertheless, in-depth understanding of the oxidative aging mechanism of epoxy asphalt binders and binding systems is still needed to enable reliable predictions of material degradation through service life. In this research, the compositional and rheological changes of epoxy asphalt, with and without filler, were analysed by means of Fourier Transform Infrared spectroscopy and Dynamic Shear Rheometer. Especially, kinetics (Arrhenius) parameters of epoxy asphalt have been determined by tracking the chemical composition changes. Oxidation of carbon species in epoxy asphalt is compositional dependent, and low values of activation energy accompany in low values of reaction rate are shown by adding epoxy in asphalt. Furthermore, the epoxy asphalt mastics (binders with filler) have been subjected to rheological testing to evaluate the stiffening effect as oxidation proceeds. Increase of modulus over a wide range of frequencies, decrease of frequency dependency of modulus of epoxy asphalt and shifting of phase angle to lower values are some important observations noticed as well. Overall, oxidation in epoxy asphalt materials occurs slowly yielding to oxygen-resistant binders when epoxy compounds are incorporated in asphalt binders.
Molecules
Organosolv lignin, a natural polymer, has been used in this study as an oxidation inhibitor in bi... more Organosolv lignin, a natural polymer, has been used in this study as an oxidation inhibitor in bitumen. Particularly, the effect of oxidative aging on the chemical compositional changes and on the rheology of bituminous binders with organosolv lignin and the impact to inhibit oxidation in bitumen were evaluated. Firstly, after analyzing the microstructure and surface characteristics of utilized organosolv lignin, a high shear mixing procedure was followed to produce binders of different proportions of lignin in bitumen. Pressure aging vessel conditioning was applied to these binders to simulate in-field aging and a series of tests were performed. Fourier transform infrared spectroscopy was used to track the compositional changes of lignin–bitumen systems before and after aging respectively. The rheological changes due to oxidative aging in the different lignin–bitumen systems were studied by means of dynamic shear rheometer tests. Based on the spectroscopic laboratory analyses, cert...
Construction and Building Materials
h i g h l i g h t s Epoxy asphalt mixes have higher tensile strength than conventional asphalt mi... more h i g h l i g h t s Epoxy asphalt mixes have higher tensile strength than conventional asphalt mixes. The four-point bending tests indicate that a high modulus material, as the epoxy asphalt, can effectively reduce deflections of specimen beams and improve their fatigue resistance. Epoxy-type tack coat improves significantly the bonding strength between two asphaltic layers. Two-layer monolithic pavements with epoxy asphalt could mitigate bonding defects of surfacing layers of enhanced strength, modulus and fatigue resistance.
Materials
This Special Issue “Sustainable Designed Pavement Materials” has been proposed and organized as a... more This Special Issue “Sustainable Designed Pavement Materials” has been proposed and organized as a means to present recent developments in the field of environmentally-friendly designed pavement materials. For this reason, articles included in this special issue relate to different aspects of pavement materials, from industry solid waste recycling to pavement materials recycling, from pavement materials modification to asphalt performance characterization, from pavement defect detection to pavement maintenance, and from asphalt pavement to cement concrete pavement, as highlighted in this editorial.
International Journal of Pavement Engineering
Waste tire rubber has been incorporated into asphalt modification for decades due to its various ... more Waste tire rubber has been incorporated into asphalt modification for decades due to its various benefits. There are two main mechanisms during bitumen-rubber interaction: rubber swelling and chemical degradation. This study surveys these two processes from the viewpoint of polymer science. The kinetics of rubber dissolution and thermodynamics of rubber swelling are discussed to provide a fundamental understanding of the interaction process and to demonstrate how optimisation of material selection and processing procedures can lead to the desired binder properties. Factors including the interaction conditions and raw material characteristics are analysed based on the previous theories and compared with experimental results.
Construction and Building Materials
h i g h l i g h t s A robust methodology was developed to evaluate the storage stability of CRMB ... more h i g h l i g h t s A robust methodology was developed to evaluate the storage stability of CRMB binders. The instability mechanism was explored by the concept of dynamic asymmetry. It is possible to manipulate raw material properties and interaction conditions to achieve a storage-stable CRMB blend.