| 1. |
- Al-Ayish, Nadia, et al.
(författare)
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Livslängden hos betongbroar: Erfarenheter och implementering med LCA/LCC
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The lifespan of construction works is crucial to achieve a low environmental impact for aprovided function. Supplementary cementitious materials are increasingly used in concrete production where the effect on the service life of structures needs to be assessed. In order to achieve a long service life, the design, flexibility in the design and workmanship also needs to be addressed.Today’s LCC and LCA analyses are based on statistics of service life of older bridges and are not material specific. There is still a lack of information about how the service life of concrete bridges is affected by different measures. The overall goal of this project was to close this information gap. The project aimed at describing key factors that affect the lifespan of concrete bridges. Key factors may reflect aspects of both durability and the utility of the design. The purpose was to investigate how the service life can be included in LCA and LCC analyses and to create a basis for future LCA and LCC analyses of concrete road bridges.Factors affecting the service life of concrete bridges have been identified through a literature survey and interviews. The studies comprised the service life of concretebridges, durability, service life models, requirements and guidelines, previous LCA and LCC studies as well as service life-extending measures throughout the whole lifecycle from material production to the end-of-life.The studies showed that reinforcement corrosion caused by chlorides is the most common cause of damage in concrete bridges where the service life of parts of theconstruction is usually shorter than the design service life. Even though frost resistance has historically been more restricting when choosing a concrete composition. The restrictions have, however, been reduced lately but there needs to be more focus on finding a design method that takes into account the impact of the concrete composition regarding reinforcement corrosion in order to find the most suitable solution for each individual case.The study shows the service life of concrete bridges depends not only on the expert’s knowledge of concrete but also on quality of execution. There is great potential to extend the service life of concrete bridges and to reduce their climate impact. However, it is important that the service life-extending measures also have a low embodied impact.The results of the survey show that technology and cost are the highest priority for mostrespondents, except for researchers where the focus is more on the environment and durability. Many also consider that contractors should set more demands towards environmentally friendly solutions.The results are compiled in the form of recommendations for reduced environmental impact and costs, as well as for how an LCA and LCC can be carried out with regard to service life.
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| 3. |
- Laurell Lyne, Åsa, 1965-
(författare)
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A Fundamental Adhesion Model for Asphalt
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- One of the mechanisms for the deterioration of asphalt is debonding. This is often referred to as stripping. Most losses of adhesion at the bitumen-aggregate interface are attributed to the action of water leading to a reduction in properties such as tensile strength, tensile stiffness and wear resistance. If we move to more accurate models for predicting bitumen-aggregate adhesion based on material properties, then we can be much more effective in building roads that are stable and resist hardening, crack-building, and stripping more effectively.The main aim of this doctoral thesis was to propose a hypothesis for what makes bitumen binders stay adhered to aggregates (or filler particles such as Portland cement) and to provide a fundamental understanding for the development of a new test method for bitumen-aggregate adhesion.The Hamaker constant was used to estimate van der Waals interactions. Hamaker’s constant is composed of two parts. The first part describes the Keesom and Debye contribution, which represents the attraction energy at zero-frequency, and the second part the London dispersive (electronic) contribution, which represents the attraction energy in the optical/UV spectrum. Calculations of Hamaker’s constant require accurate dielectric data, i.e. the dielectric constant and the refractive index of the interacting materials and the intervening medium.Paper I: Hamaker’s constant was introduced to describe and calculate the van der Waals interaction and to determine its relationship to resistance to stripping. Paper II: The dispersive component of minerals was calculated from their refractive indices using data from mineral data sheets. Paper III: The dispersive component of un-aged bitumen and aggregates was calculated from their refractive indices, determined by ellipsometery measurements.Paper IV: The surface force mapping technique, AFM QNM, was used to measure parameters such as topography, adhesion and elastic modulus simultaneously on un-aged 70/100 penetration grade bitumen binders. The result was presented as images representing individual and overlaid parameters, e.g. topographic images with an adhesion overlay and topographic images with a modulus overlay. The adhesion forces measured in the region surrounding (peri phase) the ‘bees’ (catana phase) and the region in the ‘bee’ areas are lower than the adhesion force measured in the smooth matrix (para phase). Likewise it can be observed that Young’s moduli in the region surrounding (peri phase) the ‘bees’ (catana phase) and in the ‘bees’ are higher than Young’s modulus of the smooth matrix (para phase).Paper V: The mechanism for bee formation was investigated via AFM.Paper VI: The bitumen components that are expected to migrate to the air interface and to the surface of laboratory glass slides (or to the surface of aggregates), were investigated based on the relative dielectric spectroscopic response of the material components, as determined by their dielectric constants and refractive indices.The total polarizability can be determined from the dielectric constant. The non-polar London dispersive (electronic) polarizability can be determined from refractive index measurements. In materials with higher permittivity at zero frequency the Keesom and Debye attraction energies will be responsible for a significant part of the polarization. Bitumen as a whole has a low degree of total polarizability. Bitumen contains a small fraction of n-heptane insoluble molecules that have a somewhat higher total polarizability and therefore may contribute to Debye and Keesom interactions. Bitumen as a whole is highly London dispersive (electronic) polarizable and the asphaltene (or n-heptane insoluble) fraction is even higher London dispersive (electronic) polarizable. The degree of non-polar London dispersion polarizability increases with increasing molecular size and with increasing aromaticity.Paper VII: Adhesion properties of un-aged 70/100 penetration grade bitumen binders were probed by means of permittivity analysis.The initial adhesion of non-aged bitumen binders to pure quartz aggregates is primarily London dispersive due to low total polarizability of the components.The higher surface coverage with the addition of the Portland cement to the surface of the aggregates can be explained by the addition of components with higher London dispersive polarizability and higher total polarizability of CaO, MgO and ironoxides. Portland cement is a material contributing to Debye and Keesom interactions. Portland cement could also have chemical influence on its bonding to aggregates.A strong correlation was identified between the average tangent of the dielectric loss angle in the frequency region of 0.01 to 1 Hz and surface coverage (a common method to indicate suitability of bitumen for use in roads). Surface coverage is higher for bitumen binders having a larger average loss tangent.It is suggested that the average tangent of the dielectric loss angle in the frequency range of 0.01 to 1 Hz, could be used as an indicator for predicting polarizability and thereby, adhesion potential of bitumen binders.
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| 4. |
- Laurell Lyne, Åsa, et al.
(författare)
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Adhesion between bitumen and aggregate : implementation of spectroscopic ellipsometry characterisation and estimation of Hamaker's constant
- 2013
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Ingår i: Materials and Structures. - : Springer Netherlands. - 1359-5997 .- 1871-6873. ; 46:10, s. 1737-1745
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Tidskriftsartikel (refereegranskat)abstract
- Refractive indices of seven bitumen samples and three aggregates (typical components in flexible asphalt pavement) were determined by ellipsometry in order to predict bitumen-aggregate adhesion and bitumen-bitumen cohesion using Hamaker’s constant.Hamaker’s constant according to Lifshitz was introduced to the asphalt field by two of the authors to describe and estimate van der Waal’s interaction and bitumen–aggregate adhesion. Lifshitz used the refractive index to estimate the dispersive non-polar van der Waal’s interaction component of adhesion, the predominant component in adhesion between minerals and bituminous binder. The impact of an intervening thin medium such as air or water on the adhesion can be estimated using Hamaker’s coefficient, which in turn can be related to stripping potential.The bitumen binders studied were delivered as a paving grade 70/100 according to EN 12591:2009 and came from different bitumen suppliers. The three aggregates studied were two types of granite and one diabase.It is concluded from the measurement of refractive indices and calculations of the Hamaker’s constant that there was a larger spread in refractive index among the three aggregate samples studied than among the seven bitumen samples.
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| 5. |
- Laurell Lyne, Åsa, et al.
(författare)
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Adhesive surface characteristics of bitumen binders investigated by Atomic Force Microscopy
- 2013
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 113, s. 248-256
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Tidskriftsartikel (refereegranskat)abstract
- Bitumen is a complex hydrocarbon whose composition-structure-property relationship is not well-understood. In this paper, microphase-separated topographic morphologies of unaged penetration grade 70/100 bitumen binders have been visualized by means of AFM QNM, and the relationship to local mechanical properties has been demonstrated. AFM QNM is a surface force mapping technique which measures parameters such as topography, adhesion and elastic modulus simultaneously. The resulting data can then be presented as images representing individual or overlaid parameters, e. g. topographic images with an adhesion overlay or topographic images with a modulus overlay. AFM QNM results show that the adhesive forces measured in the region surrounding (peri phase) the periodic topographic features resembling 'bees' (catana phase) and the region in the 'bee' areas are lower than the adhesive force measured in the smooth matrix (para phase). Likewise it was observed that Young's moduli in the region surrounding (peri phase) the 'bees' (catana phase) and in the 'bees' are higher than Young's modulus of the smooth matrix (para phase).
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| 6. |
- Laurell Lyne, Åsa, et al.
(författare)
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Characterization of stripping properties of stone material in asphalt
- 2013
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Ingår i: Materials and Structures. - : Rilem publications. - 1359-5997 .- 1871-6873. ; 46:1-2, s. 47-61
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Tidskriftsartikel (refereegranskat)abstract
- Aggregates and bitumen together form a composite called asphalt concrete pavement. Moisture damage to asphalt concrete pavement can occur as stripping, and is a common problem that can lead to costly repairs. There is therefore a need to understand which stone aggregates adhere best to bituminous binder and result in a minimum of stripping. Lifshitz used the refractive index to estimate the dispersive non-polar van der Waal's interaction component of adhesion, the predominant component in adhesion between minerals and bituminous binder. The impact of an intervening thin medium such as air or water on the adhesion can be estimated using Hamaker's coefficient, which in turn can be related to stripping potential. Aggregates consist of minerals and minerals consist of different elements. The objective of this study was to investigate variation in the dispersive component of minerals via their refractive indices using data from mineral data sheets. The influence of the position of elements in the periodic table and chemical composition on refractive index of minerals was examined in order to classify mineral aggregates for asphalt road building with regard to dispersive adhesive properties and expected resistance to stripping. It is clear from this study that the elemental composition of a mineral will affect its refractive index and hence its dispersive adhesion to bitumen. Aggregates and minerals have been classified according to degree of stripping in the literature. In this study it was shown that aggregates and minerals that have a refractive index higher than approximately 1.6 are expected to be less susceptible to stripping. Also, minerals containing alkali metals are sensitive to stripping since they are partially soluble in water.
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| 7. |
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| 8. |
- Laurell Lyne, Åsa, et al.
(författare)
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Interaction forces between mineral aggregates and bitumen Calculated using the Hamaker constant
- 2010
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Ingår i: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 11, s. 305-323
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Tidskriftsartikel (refereegranskat)abstract
- Moisture damages to bituminous pavements leads to costly repairs. The most serious outcome of the influence of water is the loss of adhesion between binders and aggregates. This is often described as stripping. Adhesion is the ability at a molecular level of materials to stick steadfastly to one another. An alternative way of explaining the adhesion of bitumen to aggregates is presented in this paper using the Hamaker constant, a measure of the van der Waals attraction forces between two materials. The Hamaker constant is significantly lower for water as the intervening medium than for air. For the aggregates and minerals studied, the Lifshitz-van der Waals interactions contribute 65-78 percent of the 'work of adhesion' calculated by the acid-base method. The performance of the aggregates and minerals correlates well to A(total) where resistance to stripping data is available.
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