Optimizing Chemical & Rheological Properties of Rejuvenated Bitumen

Bitumen has long been a material used in the construction of roadways, yet new pavement only consists of low fractions of recycled materials due to poor compatibility of aged bitumen and new materials. Thus, rejuvenators, chemical additives, have been used in an attempt to re-balance the chemical composition and restore the physical properties of aged bitumen back to its virgin state. A fundamental understanding of how one particular rejuvenator, soybean oil, revitalizes bitumen was investigated using a multi-scale approach. Fourier-transform infrared spectroscopy (FTIR) was used to determine the changes in chemical properties of pure and rejuvenated virgin and aged samples. Samples were artificially short term aged using a rolling thin film oven (RTFO) procedure or long term aged using a pressure aging vessel (PAV). Rejuvenator concentrations were tested at both 7.5% and 15%. FTIR results reveal carbonyl (IC=O), sulfoxide (IS=O), branched aliphatic (IB), and aromatic (IAr) indices decrease in RTFO and PAV samples from rejuvenation with soybean oil, suggesting that the aging process in the aged bitumen has been reversed. A linear amplitude sweep (LAS), a mechanical procedure using a dynamic shear rheometer (DSR), was employed to investigate rheological properties. LAS analysis of PAV samples manifests fatigue resistances of bitumen samples increase at every applied shear strain as a result of increasing concentration of rejuvenator. The relation of FTIR and LAS results indicates rejuvenation of aged bitumen with soybean oil reverses the aging process at a molecular level and, as a result, increases the fatigue life of the bitumen

Optimizing Chemical & Rheological Properties of Rejuvenated Bitumen

Bitumen has long been a material used in the construction of roadways, yet new pavement only consists of low fractions of recycled materials due to poor compatibility of aged bitumen and new materials. Thus, rejuvenators, chemical additives, have been used in an attempt to re-balance the chemical composition and restore the physical properties of aged bitumen back to its virgin state. A fundamental understanding of how one particular rejuvenator, soybean oil, revitalizes bitumen was investigated using a multi-scale approach. Fourier-transform infrared spectroscopy (FTIR) was used to determine the changes in chemical properties of pure and rejuvenated virgin and aged samples. Samples were artificially short term aged using a rolling thin film oven (RTFO) procedure or long term aged using a pressure aging vessel (PAV). Rejuvenator concentrations were tested at both 7.5% and 15%. FTIR results reveal carbonyl (IC=O), sulfoxide (IS=O), branched aliphatic (IB), and aromatic (IAr) indices decrease in RTFO and PAV samples from rejuvenation with soybean oil, suggesting that the aging process in the aged bitumen has been reversed. A linear amplitude sweep (LAS), a mechanical procedure using a dynamic shear rheometer (DSR), was employed to investigate rheological properties. LAS analysis of PAV samples manifests fatigue resistances of bitumen samples increase at every applied shear strain as a result of increasing concentration of rejuvenator. The relation of FTIR and LAS results indicates rejuvenation of aged bitumen with soybean oil reverses the aging process at a molecular level and, as a result, increases the fatigue life of the bitumen

Multiscale Research Toward Resilient Civil Infrastructure

Infrastructure materials are generally composite in nature and consist of different phases. Despite their widespread use, the mechanisms behind their behavior are often not fully understood. The aim of this research is to develop the capability to predict the performance of infrastructure based on its components, thus eliminating the need for costly experimental tests. Such an objective requires thorough understanding of material properties at various length-scales and investigation of the linkage between each scale. This approach can lead to more optimized designs, sustainable performance and maximized public benefi

Chemical-physical-mechanical Charactization of Aging and Restoration of Asphaltic Materials in Different Length Scales

Asphalt binder is a highly heterogeneous organic material; thus, its aging and restoration phenomena are very complex. Since the effects of aging and restoration on behavior of asphaltic materials are considered chemo-physical and mechanical in multiple length scales, a multiscale experimental approach can provide some significant insights to the understanding of the complex phenomenon. This study aims to investigate the laboratory aging protocol and compare it with the field aging process as well as to examine the short and long-term effects of different restorators on the mechanical, rheological, and chemical characteristics of asphaltic materials. To meet the objectives of this study, a multiscale experimental method was proposed and conducted. Three different binders (i.e. two virgin binders and one field aged binder) and restorators, a blend of different source of aggregates, and reclaimed asphalt pavement were selected/used. Test-analysis results showed that the mechanical/rheological properties and chemical analyses of the laboratory aged binders presented good correlations between aging indicators (e.g., carbonyl and colloidal index). It was also found that the long-term laboratory aging process has a limited ability to properly simulate long-term field aging. The kinetic analysis indicated that a mixed control regime, chemical reaction together with diffusion, governs the binder laboratory aging process. Test-analysis results from binders restored due to additives showed that the addition of restorators improve viscoelastic properties and fatigue resistance while they diminish rutting resistance. However, the petroleum-based restorator might contribute to maintaining the performance of the binder after another round of long-term aging. The chemical analysis indicated that the tall oil restorator contained many hydrogen bond-forming functional groups (-OH), which may increase the moisture sensitivity of the mixture. Outcomes from this study are expected to help more sustainable and energy-efficient civil infrastructure engineering due to the better selection/development of mixture components and more engineered blending of those.

Chemical-physical-mechanical Charactization of Aging and Restoration of Asphaltic Materials in Different Length Scales

Asphalt binder is a highly heterogeneous organic material; thus, its aging and restoration phenomena are very complex. Since the effects of aging and restoration on behavior of asphaltic materials are considered chemo-physical and mechanical in multiple length scales, a multiscale experimental approach can provide some significant insights to the understanding of the complex phenomenon. This study aims to investigate the laboratory aging protocol and compare it with the field aging process as well as to examine the short and long-term effects of different restorators on the mechanical, rheological, and chemical characteristics of asphaltic materials. To meet the objectives of this study, a multiscale experimental method was proposed and conducted. Three different binders (i.e. two virgin binders and one field aged binder) and restorators, a blend of different source of aggregates, and reclaimed asphalt pavement were selected/used. Test-analysis results showed that the mechanical/rheological properties and chemical analyses of the laboratory aged binders presented good correlations between aging indicators (e.g., carbonyl and colloidal index). It was also found that the long-term laboratory aging process has a limited ability to properly simulate long-term field aging. The kinetic analysis indicated that a mixed control regime, chemical reaction together with diffusion, governs the binder laboratory aging process. Test-analysis results from binders restored due to additives showed that the addition of restorators improve viscoelastic properties and fatigue resistance while they diminish rutting resistance. However, the petroleum-based restorator might contribute to maintaining the performance of the binder after another round of long-term aging. The chemical analysis indicated that the tall oil restorator contained many hydrogen bond-forming functional groups (-OH), which may increase the moisture sensitivity of the mixture. Outcomes from this study are expected to help more sustainable and energy-efficient civil infrastructure engineering due to the better selection/development of mixture components and more engineered blending of those.

Multiscale Research Toward Resilient Civil Infrastructure

Infrastructure materials are generally composite in nature and consist of different phases. Despite their widespread use, the mechanisms behind their behavior are often not fully understood. The aim of this research is to develop the capability to predict the performance of infrastructure based on its components, thus eliminating the need for costly experimental tests. Such an objective requires thorough understanding of material properties at various length-scales and investigation of the linkage between each scale. This approach can lead to more optimized designs, sustainable performance and maximized public benefi