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On investigation of stripping propensity of bituminous mixtures Bagampadde, Umaru

By: Bagampadde, UmaruPublication details: Stockholm Kungliga tekniska högskolan. Vägteknik, 2004; TRITA-VT FR 04:01, Description: 97 sSubject(s): Sweden | Thesis | Bituminous mixture | | Moisture | Rheology | Chemistry | Properties | Penetration | Softening | Viscosity | Ductility | Viscoelasticity | Chromatography | Susceptibility | Aggregate | Bitumen | | 51Online resources: Publikation/Publication Bibl.nr: VTI P4856:2004-01Location: Abstract: In this study, an experimental programme was designed to establish a relationship between bituminous mixture constituent material properties and their propensity to moisture induced damage in form of stripping. Six bitumen types (3 from Uganda and 3 from Sweden) with presumably varying characteristics were evaluated basing on rheology and chemistry. Eleven aggregates were used in this study. Seven were sourced from active quarries in Uganda and four were from Sweden. Bitumen rheology was established basing on penetration, softening point, viscosity, ductility and visco-elastic parameters obtained from dynamic mechanical analysis. Bitumen chemistry was studied using Fourier Transform Infrared Spectroscopy, Gel Permeation Chromatography (GPC) and Thin Layer Chromatography (TLC). Bituminous mixtures were reconstituted from the bitumen and aggregate combinations basing on the Swedish mix design procedure ROAD 94 using dense graded mixtures with 16mm maximum aggregate size (AG16). Mixture sensitivity to moisture was evaluated basing on Swedish FAS 446-98 specifications closely related to the modified Lottman procedure. The investigation was done in two phases namely, (a) the effect of aggregate properties on mixture moisture sensitivity and (b) the of cross effects of bitumen and aggregates on mixture moisture sensitivity. The results reveal chemical compositional differences in bitumens that would be considered similar basing on classical rheological properties like penetration and viscosity. Results of dynamic mechanical analysis show that binders have similar visco-elastic response around 0oC. This could be a potential phenomenon to serve as a grading scheme for bitumen as is the case with penetration and viscosity grading systems. The results from phase I of the study show that presence of Ca-feldspars and ferromagnesian minerals in aggregates largely relates to improved resistance of mixtures to moisture damage. In addition, mixtures from aggregates with high concentrations of acid insolubles (SiO2 and Al2O3) are sensitive to moisture damage. The results of phase II of this study show that the choice of aggregate type is the dominant factor affecting moisture sensitivity of the resulting mixtures. Bitumen type seems not to be an important factor in determining moisture sensitivity of bituminous mixtures. Aggregates with Ca-feldspars and ferromagnesian minerals seemed to be the most resistant to moisture damage irrespective of the bitumen type. Assessment of moisture sensitivity basing on absolute stiffness values of water treated mixtures seems not to be reliable. Results from this study show that mixtures with similar wet resilient moduli had varying tensile strength ratios, hence varying moisture sensitivity tendencies. Modulus of resilience ratio (MRR) and tensile strength ratio (TSR) parameters show similar trends in comparing moisture sensitivity of different mixtures. However, MRR values are generally lower than TSR values for the same mixtures.
Item type: Reports, conferences, monographs
Holdings: VTI P4856:2004-01

In this study, an experimental programme was designed to establish a relationship between bituminous mixture constituent material properties and their propensity to moisture induced damage in form of stripping. Six bitumen types (3 from Uganda and 3 from Sweden) with presumably varying characteristics were evaluated basing on rheology and chemistry. Eleven aggregates were used in this study. Seven were sourced from active quarries in Uganda and four were from Sweden. Bitumen rheology was established basing on penetration, softening point, viscosity, ductility and visco-elastic parameters obtained from dynamic mechanical analysis. Bitumen chemistry was studied using Fourier Transform Infrared Spectroscopy, Gel Permeation Chromatography (GPC) and Thin Layer Chromatography (TLC). Bituminous mixtures were reconstituted from the bitumen and aggregate combinations basing on the Swedish mix design procedure ROAD 94 using dense graded mixtures with 16mm maximum aggregate size (AG16). Mixture sensitivity to moisture was evaluated basing on Swedish FAS 446-98 specifications closely related to the modified Lottman procedure. The investigation was done in two phases namely, (a) the effect of aggregate properties on mixture moisture sensitivity and (b) the of cross effects of bitumen and aggregates on mixture moisture sensitivity. The results reveal chemical compositional differences in bitumens that would be considered similar basing on classical rheological properties like penetration and viscosity. Results of dynamic mechanical analysis show that binders have similar visco-elastic response around 0oC. This could be a potential phenomenon to serve as a grading scheme for bitumen as is the case with penetration and viscosity grading systems. The results from phase I of the study show that presence of Ca-feldspars and ferromagnesian minerals in aggregates largely relates to improved resistance of mixtures to moisture damage. In addition, mixtures from aggregates with high concentrations of acid insolubles (SiO2 and Al2O3) are sensitive to moisture damage. The results of phase II of this study show that the choice of aggregate type is the dominant factor affecting moisture sensitivity of the resulting mixtures. Bitumen type seems not to be an important factor in determining moisture sensitivity of bituminous mixtures. Aggregates with Ca-feldspars and ferromagnesian minerals seemed to be the most resistant to moisture damage irrespective of the bitumen type. Assessment of moisture sensitivity basing on absolute stiffness values of water treated mixtures seems not to be reliable. Results from this study show that mixtures with similar wet resilient moduli had varying tensile strength ratios, hence varying moisture sensitivity tendencies. Modulus of resilience ratio (MRR) and tensile strength ratio (TSR) parameters show similar trends in comparing moisture sensitivity of different mixtures. However, MRR values are generally lower than TSR values for the same mixtures.

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