| 1. |
- Bagampadde, Umaru, et al.
(författare)
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Influence of aggregate chemical and mineralogical composition on stripping in bituminous mixtures
- 2005
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Ingår i: The international journal of pavement engineering. - : Informa UK Limited. - 1029-8436 .- 1477-268X. ; 6:4, s. 229-239
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Ekblad, Jonas, et al.
(författare)
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Influence of water and mica content on resilient properties of coarse granular materials
- 2008
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Ingår i: The international journal of pavement engineering. - : Informa UK Limited. - 1029-8436 .- 1477-268X. ; 9:3, s. 215-227
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Tidskriftsartikel (refereegranskat)abstract
- Elevated amounts of free mica particles in unbound granular materials used in road construction are believed to detrimentally influence bearing capacity. The objective of presented work was to investigate the influence of mica content on resilient properties of coarse granular material (maximum particle size 63mm) under varying water contents. The test scheme comprised triaxial tests, using constant confining pressures, at incrementally raised water contents up to practically full saturation. Increased mica content was achieved by replacing a part of the base material grading smaller than 4mm, with an equal amount of pure muscovite mica of similar grading, hence keeping the overall particle size distribution unchanged. Generally, resilient modulus decreased with increased mica content and elevated water contents caused reduction in stiffness. In relative terms, the reduction in resilient modulus caused by water decreased with increased mica content.
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| 3. |
- Kringos, Nicole, et al.
(författare)
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Modeling of combined physical-mechanical moisture induced damage in asphaltic mixes : Part 1: governing processes and formulations
- 2008
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Ingår i: The international journal of pavement engineering. - : Informa UK Limited. - 1029-8436 .- 1477-268X. ; 9:2, s. 115-128
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Tidskriftsartikel (refereegranskat)abstract
- Moisturehas for a long time been recognised as a serious contributor to premature degradation ofasphalticpavements. Many studies have been performed to collect, describe and measure themoisturesusceptibility ofasphalticmixes. Most of these are aimed at a comparative measure ofmoisturedamage, either via visual observations from field data or laboratory tests or viamechanicaltests, which give a so calledmoisturedamageindex parameter. The research presented in this paper ispartof an ongoing effort at Delft University of Technology, to move away from such comparative or empirical measures ofmoisture-induceddamageand start treatingmoisture-induceddamagein a comprehensive energy based framework. Such a framework would enable realistic predictions and time-assessment of the failure pattern occurring in anasphalticpavement under the given environmental and traffic loading which could be rutting, cracking, ravelling or any combination or manifestation thereof. Themodellingofmoisture-induceddamageis a complex problem, which involves a coupling betweenphysicalandmechanicaldamageprocesses. This paper discusses several modes ofmoistureinfiltration intoasphalticmixesand derives thegoverningequations for their simulations.Moisturediffusion into the mastic film, towards the aggregate-mastic interface and mastic erosion, due to high water pressures caused by the pumping action of traffic loading, are identified as the mainmoisture-induceddamageprocessesand are implemented in a new finite element program, named RoAM. The paper discusses the necessary model parameters and gives detailed verification of themoisturediffusion and advective transport simulations. In the accompanying paper the developed finite element model is demonstrated via an elaborate parametric study and the fundamentalmoisture-induceddamageparameters are discussed.
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| 4. |
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| 5. |
- Loorents, Karl Johan, et al.
(författare)
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On mineralogical composition of filler and performance of asphalt concrete
- 2009
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Ingår i: The international journal of pavement engineering. - : Informa UK Limited. - 1029-8436 .- 1477-268X. ; 10:4, s. 299-309
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that mineral fillers have an important influence on the performance of asphalt mixes. For example, usually micaceous fillers are disregarded in manufacturing asphalt mixes. Substituting the fine fraction in an asphalt mixture with a fine fraction of a noticeably different material with respect to physical-mineralogical properties will change the asphalt mixture properties and its performance in the field, especially under severe winter condition. The effect of the surface area of the fine materials is already known, however, the present paper studies mineralogically related factors of the filler fraction that influences the asphalt concrete resistance against water impact and freeze-thaw cycles. Five fillers derived from common crushed rock aggregates for construction purposes were analysed. The samples have been mineralogically characterised, the specific surface area (SSA) has been determined together with geometrical parameters and surface texture to differentiate between samples. The analysed data confirms a correlation between the SSA and mineralogical composition of fine material and the deterioration of the stiffness modulus of asphalt concrete under severe winter condition. This study indicates the vitality of the mineralogical composition of the fine material for the performance of bituminous layers. This work should give rise to better quality assurance and economise on natural resources in the production of asphalt mixes.
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| 6. |
- Said, Safwat, 1951-, et al.
(författare)
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Impact of mica content on water sensitivity of asphalt concrete
- 2009
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Ingår i: The international journal of pavement engineering. - : Informa UK Limited. - 1029-8436 .- 1477-268X. ; 10:1, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that mineral fillers have an important influence on the performance of bituminous mixtures. Properties of filler are depending on the type and the nature of mineral filler. Experience has shown that presence of mica in the filler material has reduced the asphalt concrete resistance against water influence and freeze and thaw cycles. The purpose of the present work is to clarify the effect of free mica in the filler material on the durability of bituminous mixtures. Presence of free mica results in a tremendous increase of the total surface area of aggregate, which is intended to be covered by a bitumen film. It is concluded that making mix design in respect to surface area of the filler will almost vanish the disadvantage of using mica in production of asphalt mixtures. It will also result in using less amount of mineral filler.
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