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  • 1.
    Bagampadde, Umaru
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Investigations on moisture damage-related behaviour of bituminous materials2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This doctoral thesis presents results of literature review on classical and contemporary aspects of stripping, as well as experimental investigations on moisture damage as influenced by bituminous materials.

    Previous research in the area of moisture damage was reviewed and synthesized into a state-of-the-art. Important parameters linked to moisture sensitivity, like bituminous material characteristics, dynamic loads from heavy vehicles, environmental factors, construction practice and nature of anti-stripping additives, are presented. The state-of-the-art in current test methods is summarized and given.

    The experimental work involved investigations of the influence of bitumen and aggregate composition on water susceptibility. The influence of aggregate mineralogy and chemistry was evaluated using eleven aggregates and one bitumen, followed by studying the interactive effect of four bitumens and four aggregates. Moisture sensitivity was evaluated in accordance with (EN 12697-12:2003) for conditioning, ASTM D 4123 for resilient modulus determination, and (EN 12697-23:2003) for indirect tensile strength testing. Furthermore, thermal stability of two liquid amine anti-stripping additives mixed with two bitumens of varied acidity was investigated using potentiometric titration and Fourier Transform Infrared (FTIR) Spectroscopy. Lastly, a technique based on Fourier Transform Infrared Spectroscopy-Attenuated Total Reflectance (FTIR-ATR) was developed and used for studying transport of water across thin bitumen films, as well as stripping at bitumen/substrate interfaces. Bitumens from different sources and three substrates (silicon, germanium and zinc selenide crystals) were used. Based on the results obtained, it was concluded that aggregates containing sodium and potassium in alkali feldspars generally showed high moisture sensitivity. In contrast, presence of calcium, magnesium and iron was associated with aggregates with low moisture sensitivity. Contrary to several previous findings, one aggregate with practically 100% quartz exhibited low moisture sensitivity. No linear relationship between moisture sensitivity and the contents of SiO2 and Al2O3 in the aggregates studied was established. Results of the interactive influence of bitumen and aggregate composition showed that high acid and low penetration bitumens exhibited high dry strength for all the aggregates studied. On the other hand, for a given bitumen, the wet strengths were found to be aggregate specific.

    The results of tests on thermal stability of amine additives showed that usefulness of these additives reduces considerably, when the more alkaline additive was mixed with the high acid bitumen, followed by storing the blends under pronounced conditions of time and temperature (24 hours and 140ºC, or more, in this study). Much less interaction occurred when the less alkaline additive was blended with the low acid bitumen. Even if a correlation was found between the results of potentiometric titration and Fourier Transform Infrared spectroscopy, the latter was not considered good enough at detecting amine additives, especially at low dosages.

    The technique based on FTIR-ATR developed in this study distinguished between good and bad bitumens with regard to stripping. The effectiveness of amine-based additives in reducing stripping was also shown by the method. Three likely processes occurred during the test, namely water diffusion, film break, and displacement (stripping) of bitumen from the substrate surface. The results also indicated that the diffusion process of water into the bitumen/substrate interface does not obey Fick’s law.

  • 2.
    Bagampadde, Umaru
    KTH, Superseded Departments, Civil and Architectural Engineering.
    On investigation of stripping propensity of bituminous mixtures2004Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    In this study, an experimental programme was designed toestablish a relationship between bituminous mixture constituentmaterial properties and their propensity to moisture induceddamage in form of stripping. Six bitumen types (3 from Ugandaand 3 from Sweden) with presumably varying characteristics wereevaluated basing on rheology and chemistry. Eleven aggregateswere used in this study. Seven were sourced from activequarries in Uganda and four were from Sweden.

    Bitumen rheology was established basing on penetration,softening point, viscosity, ductility and visco-elasticparameters obtained from dynamic mechanical analysis. Bitumenchemistry was studied using Fourier Transform InfraredSpectroscopy, Gel Permeation Chromatography (GPC) and ThinLayer Chromatography (TLC).

    Bituminous mixtures were reconstituted from the bitumen andaggregate combinations basing on the Swedish mix designprocedure ROAD 94 using dense graded mixtures with 16mm maximumaggregate size (AG16). Mixture sensitivity to moisture wasevaluated basing on Swedish FAS 446-98 specifications closelyrelated to the modified Lottman procedure.

    The investigation was done in two phases namely, (a) theeffect of aggregate properties on mixture moisture sensitivityand (b) the of cross effects of bitumen and aggregates onmixture moisture sensitivity.

    The results reveal chemical compositional differences inbitumens that would be considered similar basing on classicalrheological properties like penetration and viscosity. Resultsof dynamic mechanical analysis show that binders have similarvisco-elastic response around 0oC. This could be a potentialphenomenon to serve as a grading scheme for bitumen as is thecase with penetration and viscosity grading systems.

    The results from phase I of the study show that presence ofCa-feldspars and ferromagnesian minerals in aggregates largelyrelates to improved resistance of mixtures to moisture damage.In addition, mixtures from aggregates with high concentrationsof acid insolubles (SiO2 and Al2O3) are sensitive to moisturedamage.

    The results of phase II of this study show that the choiceof aggregate type is the dominant factor affecting moisturesensitivity of the resulting mixtures. Bitumen type seems notto be an important factor in determining moisture sensitivityof bituminous mixtures. Aggregates with Ca-feldspars andferromagnesian minerals seemed to be the most resistant tomoisture damage irrespective of the bitumen type.

    Assessment of moisture sensitivity basing on absolutestiffness values of water treated mixtures seems not to bereliable. Results from this study show that mixtures withsimilar wet resilient moduli had varying tensile strengthratios, hence varying moisture sensitivity tendencies. Modulusof resilience ratio (MRR) and tensile strength ratio (TSR)parameters show similar trends in comparing moisturesensitivity of different mixtures. However, MRR values aregenerally lower than TSR values for the same mixtures.

  • 3.
    Bagampadde, Umaru
    et al.
    Faculty of Technology, Makerere University, Kampala.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Characterization of chemical reactivity of liquid antistripping additives using potentiometric titration and FTIR spectroscopy2006In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 20, no 5, p. 2174-2180Article in journal (Refereed)
    Abstract [en]

    Chemical reactivity of two liquid antistripping additives mixed with two bitumens of diverse acid numbers was evaluated. Additives present in the blends were detected by use of potentiometric titration and infrared spectroscopy. Tests were done at dosages of 0, 0.5, 1.0, and 2.0%; storage temperatures of 25, 100, 140, and 150 degrees C; and storage times of 1, 24, and 72 h. At 0.5% dosage, close to typical field values, the more basic additive mixed with bitumen of high acid number almost ceased to be detected after 24 h of storage at 140 degrees C. The less basic additive could be detected beyond these conditions, irrespective of the bitumen used. At higher dosages, reactions with the bitumens were found to be more pronounced with the more basic additive. The reactions between the additives and bitumens studied seemed to be higher in the bitumen with higher acid number, irrespective of the dosage. Statistical analysis indicated that all the parameters studied significantly affected change in amount of additives detected in the blends. A correlation was established between potentiometric titration and infrared spectroscopy in detecting amine additives. This correlation notwithstanding, infrared spectroscopy was found to not be a good tool for measuring amines in the blends, especially at low concentrations.

  • 4.
    Bagampadde, Umaru
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Kiggundu, B
    Fundamentals of Stripping in Bituminous Pavements - State of the Art2003Report (Other academic)
  • 5.
    Bagampadde, Umaru
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Kiggundu, B
    Fundamentals of Stripping in Bituminous Pavements -State of the Art2003Report (Other academic)
  • 6.
    Bagampadde, Umaru
    et al.
    KTH, Superseded Departments, Civil and Architectural Engineering.
    Isacsson, Ulf
    KTH, Superseded Departments, Civil and Architectural Engineering.
    Kiggundu, Bob
    KTH, Superseded Departments, Civil and Architectural Engineering.
    Classical and contemporary aspects of stripping in bituminous mixtures2004In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 5, no 1, p. 7-45Article in journal (Refereed)
    Abstract [en]

    Stripping or removal of bitumen from an aggregate because of water penetrating into the interface causes many pavements to fail. Stripping has been existent since the advent of paving technology. It causes functional weakening of pavements leading to costly repairs. This state-of-the-art paper deals with important concepts of stripping as, bitumen chemistry and rheology, aggregate properties (chemical and mineralogical composition, surface texture, morphology, porosity, etc), traffic, water properties, construction practices (mixing, placement and in-service drainage) and nature of antistripping additives. Adhesion of bitumen onto aggregate is explained based on theories like mechanistic tenacity, molecular orientation, chemical reaction, and thermodynamic balance of interfacial forces. Stripping is elucidated using several mechanisms namely, displacement, detachment, spontaneous emulsification, bitumen film rupture, water pore pressure, hydraulic scouring, chemical disbanding, microbial activity, osmosis; and blistering and pitting. Attendant theories to the mechanisms are explained. Moisture sensitivity test methods emerged are described and discussed. The large number of tests that have evolved shows the importance of the phenomenon of stripping. Remedial measures which include use of antistripping additives, careful selection of hot mix component materials, good construction practice, and others have been proposed for use in practice.

  • 7.
    Bagampadde, Umaru
    et al.
    Makerere University, Kampala.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Kiggundu, Bob
    Makerere University, Kampala.
    Impact of bitumen and aggregate composition on stripping in bituminous mixtures2006In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 39, no 287, p. 303-315Article in journal (Refereed)
    Abstract [en]

    The impact of bitumen and aggregate composition on stripping was investigated using four bitumens and four aggregates. Moisture sensitivity was assessed based on retained resilient modulus and tensile strength ratio (MRR and TSR, respectively). The results indicate that mixtures from the bitumen with a high acid number exhibited high resilient modulus and tensile strength in the dry condition for all the aggregates. In wet condition, this conclusion did also hold except for one aggregate. Regarding penetration grade, mixtures made with lower penetration grade bitumen exhibited higher resilient modulus and tensile strength, in dry and wet conditions, than those of higher penetration grade. Bitumen characteristics like acid number, penetration grade and molecular size distribution did not influence moisture sensitivity. Mixtures with aggregates containing alkali metals (sodium and potassium) exhibited relatively high moisture sensitivity, regardless of the bitumen used. In contrast, indications of moisture sensitivity were not apparent in mixtures made with aggregates containing calcium, magnesium and iron. Data analysis revealed that variability in moisture sensitivity is attributed to aggregate rather than bitumen. No significant interaction effect between bitumen and aggregate was found on moisture sensitivity. The results indicated good correlation between MRR and TSR in ranking mixtures for stripping.

  • 8.
    Bagampadde, Umaru
    et al.
    Makerere University, Kampala.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Kiggundu, Bob
    Makerere University, Kampala.
    Influence of aggregate chemical and mineralogical composition on stripping in bituminous mixtures2005In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 6, no 4, p. 229-239Article in journal (Refereed)
    Abstract [en]

    The influence of aggregate chemical and mineralogical composition on moisture sensitivity was investigated using 11 aggregates from typical tropical and temperate climates and one bitumen. Mix design and compaction were based on Swedish Road 94 hot mix base specifications and moisture damage was determined using resilient modulus and tensile strength ratios. As much as practically possible, air voids, gradation, compaction level, bitumen content and curing were controlled. Mixtures from aggregates containing sodium and potassium exhibited relatively high moisture sensitivity. The converse was apparent for aggregates with calcium, magnesium and iron. No significant correlation was observed between the strength ratios and contents of Al2O3 and SiO2. Stripping was generally high for aggregates with quartz and alkali feldspars, although one aggregate with practically 100% quartz showed low moisture sensitivity. Statistical analysis showed good correlation between resilient modulus and tensile strength ratios.

  • 9.
    Bagampadde, Umaru
    et al.
    Makerere University, Kampala.
    Karlsson, R.
    KTH.
    Laboratory studies on stripping at bitumen/substrate interfaces using FTIR-ATR2007In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 42, no 9, p. 3197-3206Article in journal (Refereed)
    Abstract [en]

    A technique based on Fourier Transform Infrared Spectroscopy-Attenuated Total Reflectance (FTIR-ATR) was developed and used to study movement of water into bitumen/substrate interfaces, as well as to characterize stripping. Bitumens from different sources were used and applied on various substrates (silicon, germanium and zinc selenide) as thin films. The influence of bitumen type, substrate type, temperature, film thickness and modification with amines, on water damage was studied. The technique gave information on water flow into interfaces and how stripping possibly occurs. It distinguished between stripping and non-stripping bitumens. At least one of three processes occurred, namely water diffusion, film fracture, and bitumen displacement by water, respectively. The diffusion of water did not obey Fick's law. Stripping was influenced by bitumen source when silicon and germanium substrates were used. Notching the films made the process of water entry almost occur immediately. Additives significantly reduced stripping in the moisture-sensitive bitumen on silicon and germanium substrates, even after film notching. Although, good agreement was observed between tests for the bitumens that did not strip, the tests on stripping bitumens showed poor agreement.

  • 10.
    Bagampadde, Umaru
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Kiggundu, B
    Exploratory Stripping Investigations on Bituminous Mixtures in Uganda2002Conference paper (Refereed)
  • 11.
    Bagampadde, Umaru
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering (closed 20110301).
    Kiggundu, B. M.
    Influence of truck load channelization on stripping in asphalt mixtures2007In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 21, no 8, p. 1628-1635Article in journal (Refereed)
    Abstract [en]

    The influence of load channelization on stripping was investigated using cores and block samples from a heavily loaded highway. The original 80/100 asphalt (virgin and RTFOT aged) was characterized using conventional methods. Stripping of mixtures was measured using ASTM D1664 and that of cores using visual diametral plane rating and loss in indirect tensile strength due to soaking. The pore saturation and air voids were found to be influenced by ground water level and wheel track location across traffic lanes. Stripping was rated higher in the wheel paths than between wheel paths, especially in shallow water table areas where it was observed to be 82% higher, implying possible dependency of stripping on channelization. To enhance resistance to moisture damage, it is recommended that Hot Mix Asphalt surfaces in areas with shallow water tables be designed to a more favorable refusal density.

  • 12.
    Namutebi, May
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering (closed 20110301).
    Bagampadde, Umaru
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering (closed 20110301).
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering (closed 20110301).
    Stabilization of Road Construction Materials using Foamed Bitumen, State-of-the-Art Review2009Report (Other academic)
1 - 12 of 12
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