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This study, part of the NCHRP 9-45 Project, analyzed the effect of mineral filler properties on asphalt mastic and the rutting potential of asphaltic mixture. The mineral filler properties were characterized by four tests: Rigden voids (RV), fineness modulus (FM), calcium oxide (CaO) content, and methylene blue value. The rheological properties of asphalt binder and mastic were characterized with the use of apparent viscosity and multiple stress creep recovery tests. Dynamic modulus and flow number tests were conducted to examine the asphaltic mixture rutting potential. The tested mixtures included several variables: four asphalt binder types, including virgin and polymer modified; two aggregate gradations; and a selected group of fillers. The study concluded that asphalt mastic performance was significantly affected by the fractional voids in the filler and possibly by the CaO content and FM. This effect, however, depended on binder type. On the one hand, the styrene-butadiene-styrene modified binder showed the strongest effect as a result of the mineral filler inclusion when tested as mastic. On the other hand, RV and CaO content showed relatively greater correlation with the mixture rutting potential, as compared with other filler properties. Addition of RV improved the prediction models for dynamic modulus and flow number. The effect of RV on the mixture rutting potential was more pronounced for the coarse mixture than for the fine mixture.

This study, part of the NCHRP 9–45 Project, analyzed the effect of mineral filler properties on asphalt mastic and the rutting potential of asphaltic mixture. The mineral filler properties were characterized by four tests: Rigden voids (RV), fineness modulus (FM), calcium oxide (CaO) content, and methylene blue value. The rheological properties of asphalt binder and mastic were characterized with the use of apparent viscosity and multiple stress creep recovery tests. Dynamic modulus and flow number tests were conducted to examine the asphaltic mixture rutting potential. The tested mixtures included several variables: four asphalt binder types, including virgin and polymer modified; two aggregate gradations; and a selected group of fillers. The study concluded that asphalt mastic performance was significantly affected by the fractional voids in the filler and possibly by the CaO content and FM. This effect, however, depended on binder type. On the one hand, the styrene–butadiene–styrene modified binder showed the strongest effect as a result of the mineral filler inclusion when tested as mastic. On the other hand, RV and CaO content showed relatively greater correlation with the mixture rutting potential, as compared with other filler properties. Addition of RV improved the prediction models for dynamic modulus and flow number. The effect of RV on the mixture rutting potential was more pronounced for the coarse mixture than for the fine mixture.

Hot-poured bituminous crack sealing has been widely accepted as a routine preventative maintenance practice. With proper installation, the sealing is expected to extend pavement service life by 3 to 5 years. However, current specifications for selection of crack sealants correlate poorly with field performance; hence, a set of new testing methods, based on sealant rheological and mechanical properties, was developed recently. Measurements of the mechanical properties of crack sealant at low temperatures are among the criteria introduced as part of the developed performance-based guidelines. The main purpose of this study was to identify and validate the low-temperature selection thresholds for the newly developed performance-based guidelines for selecting hot-poured bituminous crack sealants. In this study, selection criteria for crack sealant bending beam rheometer (CSBBR) and crack sealant direct tension tester (CSDTT) tests were identified. Two performance parameters for CSBBR test were used for the selection criteria: stiffness at 240 s and average creep rate (ACR). Both parameters were identified by comparing laboratory testing results with known sealant field performance, obtained from a long-term study in Canada. The selection criterion for the CSDTT test was extendibility, on the basis of field values reported in the literature. The recommended selection criteria were used to predict the field performance of 12 sealants evaluated by the National Transportation Product Evaluation Program (NTPEP). Results showed good correlation between the proposed selection thresholds and NTPEP field sealant performance.

Hot-poured bituminous crack sealing has been widely accepted as a routine preventative maintenance practice. With proper installation, the sealing is expected to extend pavement service life by 3 to 5 years. However, current specifications for selection of crack sealants correlate poorly with field performance; hence, a set of new testing methods, based on sealant rheological and mechanical properties, was developed recently. Measurements of the mechanical properties of crack sealant at low temperatures are among the criteria introduced as part of the developed performance-based guidelines. The main purpose of this study was to identify and validate the low-temperature selection thresholds for the newly developed performance-based guidelines for selecting hot-poured bituminous crack sealants. In this study, selection criteria for crack sealant bending beam rheometer (CSBBR) and crack sealant direct tension tester (CSDTT) tests were identified. Two performance parameters for CSBBR test were used for the selection criteria: stiffness at 240 s and average creep rate (ACR). Both parameters were identified by comparing laboratory testing results with known sealant field performance, obtained from a long-term study in Canada. The selection criterion for the CSDTT test was extendibility, on the basis of field values reported in the literature. The recommended selection criteria were used to predict the field performance of 12 sealants evaluated by the National Transportation Product Evaluation Program (NTPEP). Results showed good correlation between the proposed selection thresholds and NTPEP field sealant performance.

Despite the possible benefits of implementing asphalt binder film thickness into current specifications to address durability problems, most of the related research has been theoretical and only a few attempts have been made to measure this property experimentally. The objective of this study was to investigate the concept of asphalt binder film thickness experimentally on the basis of measurements obtained by image analysis techniques, reflective light microscopy, and scanning electron microscopy. The results of the experimental program were used to gain insight into the concept of asphalt binder film thickness and its validity. Experimental results indicated that asphalt binder films coating large aggregates do not actually exist in hot-mix asphalt. Instead, what are referred to as asphalt binder films surrounding large aggregates are actually asphalt mastic films. These films are highly irregular in shape and have a thickness greater than 100 μm in the mixture considered in this study. The asphalt binder films in the mastic were observed at a thickness of 2 μm in the mixtures considered. However, these entities do not represent asphalt binder coatings around aggregates; they are only part of a blend with fine aggregates and mineral fillers. Microscopic analysis showed that air voids usually appear near the boundary between large aggregates and asphalt mastic.

Despite the possible benefits of implementing asphalt binder film thickness into current specifications to address durability problems, most of the related research has been theoretical and only a few attempts have been made to measure this property experimentally. The objective of this study was to investigate the concept of asphalt binder film thickness experimentally on the basis of measurements obtained by image analysis techniques, reflective light microscopy, and scanning electron microscopy. The results of the experimental program were used to gain insight into the concept of asphalt binder film thickness and its validity. Experimental results indicated that asphalt binder films coating large aggregates do not actually exist in hot-mix asphalt. Instead, what are referred to as asphalt binder films surrounding large aggregates are actually asphalt mastic films. These films are highly irregular in shape and have a thickness greater than 100 µm in the mixture considered in this study. The asphalt binder films in the mastic were observed at a thickness of 2 µm in the mixtures considered. However, these entities do not represent asphalt binder coatings around aggregates; they are only part of a blend with fine aggregates and mineral fillers. Microscopic analysis showed that air voids usually appear near the boundary between large aggregates and asphalt mastic.

To establish a clear understanding of the behavior of hot-poured bituminous-based crack sealants at low service temperature and to predict their field performance, the constitutive stress–strain relationship must be described. The description of this relationship would allow accurate prediction of crack sealants’ field responses to thermal and traffic loading. The objective of this paper is to describe crack sealant constitutive behavior at low temperature by linear viscoelastic modeling (Prony series expansion). The suggested model was fitted to creep measurements obtained from a modified bending beam rheometer test setup. The experimental program included testing of three soft crack sealants having a relatively high level of polymer modification content at a temperature ranging from -28°C to -40°C. A Prony series expansion was fitted to the experimental results. To determine the time-dependent responses of crack sealants to a constant creep load, the fitted material parameters were incorporated into a three-dimensional finite element model. Measured and calculated deflections were in good agreement. This finding suggests that the constitutive behavior of crack sealants can be accurately described by the linear viscoelastic regime at low service temperatures.

To establish a clear understanding of the behavior of hot-poured bituminous-based crack sealants at low service temperature and to predict their field performance, the constitutive stress-strain relationship must be described. The description of this relationship would allow accurate prediction of crack sealants' field responses to thermal and traffic loading. The objective of this paper is to describe crack sealant constitutive behavior at low temperature by linear viscoelastic modeling (Prony series expansion). The suggested model was fitted to creep measurements obtained from a modified bending beam rheometer test setup. The experimental program included testing of three soft crack sealants having a relatively high level of polymer modification content at a temperature ranging from —28°C to —40°C. A Prony series expansion was fitted to the experimental results. To determine the time-dependent responses of crack sealants to a constant creep load, the fitted material parameters were incorporated into a three-dimensional finite element model. Measured and calculated deflections were in good agreement. This finding suggests that the constitutive behavior of crack sealants can be accurately described by the linear viscoelastic regime at low service temperatures.