| 1. |
- Al-Ayish, Nadia
(författare)
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Environmental Impact of Concrete Structures - with Focus on Durability and Resource Efficiency
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Concrete is essential for the construction industry with characteristic properties that make it irreplaceable in some aspects. However, due to the large volumes consumed and the energy intense cement clinker production it also has a notable climate impact. In order to reach the international and national sustainability goals it is therefore important to reduce the climate impact of concrete structures.There are many ways to influence the environmental impact of concrete and a detailed analysis is one of the actions that could push the industry and the society towards a sustainable development. The purpose of this research is to evaluate the environmental impact of concrete structures and the built environment and to highlight the possibilities to reduce that impact with choice of concrete mix and innovative design solutions.A life cycle assessment (LCA) was carried out to analyze the environmental impact of two thin façade solutions with innovative materials and to evaluate influences of different greenhouse gas reducing measures on concrete bridges. The influence of supplementary cementitious materials (SCM) in terms of climate impact and durability was also analyzed.The results indicate that SCMs have a twofold effect on the climate impact of reinforced concrete structures. Not only do they reduce the greenhouse gases through cement clinker replacement but also by an improvement of durability regarding chloride ingress. Currently, this is not considered in the regulations, which makes it difficult to foresee in LCA at early design stages. The results also show great possibilities to reduce the climate impact through different measures and design alternatives and the need for further development of products and solutions.
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| 2. |
- Andersson, Ronny, et al.
(författare)
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Calculating CO2 Uptake for Existing Concrete Structures during and after Service Life
- 2013
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Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 1520-5851 .- 0013-936X. ; 47:20, s. 11625-11633
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a model that can calculate the uptake of CO2 in all existing concrete structures, including its uptake after service life. This is important for the calculation of the total CO2 uptake in the society and its time dependence. The model uses the well-documented cement use and knowledge of how the investments are distributed throughout the building sector to estimate the stock of concrete applications in a country. The depth of carbonation of these applications is estimated using two models, one theoretical and one based on field measurements. The maximum theoretical uptake potential is defined as the amount of CO2 that is emitted during calcination at the production of Portland cement, but the model can also, with some adjustments, be used for the other cement types. The model has been applied on data from Sweden and the results show a CO2 uptake in 2011 in all existing structures of about 300 000 tonnes, which corresponds to about 17% of the total emissions (calcination and fuel) from the production of new cement for use in Sweden in the same year. The study also shows that in the years 2030 and 2050, an increase in the uptake in crushed concrete, from 12 000 tonnes today to 200 000 and 500 000 tonnes of CO2, respectively, could be possible if the waste handling is redesigned.
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| 3. |
- Boubitsas, Dimitiros, et al.
(författare)
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Frost Resistance of Concrete – Experience from Long-Term Field Exposure
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report presents the results from a research project financed by Trafikverket, the Swedish Transport Administration, co-financed by Cementa AB.The purpose of this project is to investigate concrete specimens exposed to a de-icing salt highway environment at Highway 40 close to Borås after about 20 years. The project work was divided into two parts: Part One for frost resistance of concrete and Part Two for chloride ingress and reinforcement corrosion.In Part One, more than 100 types of concrete mixes with different binder types/combinations, water-binder ratios (w/b) and air contents exposed at three field test sites were examined for external and internal frost damage by measurements of the changes in volume of, and in ultrasonic transmission time through, the specimens. Furthermore, some laboratory tests were carried out to supply necessary data for modelling and identify the possible mechanisms causing frost damage.The results show clearly that the highway environment is the most aggressive with regard to external frost damage. Further, the results from this study show that the existence of entrained air and the water-binder ratio are the main parameters influencing the resistance of concrete to external salt-frost damage. Furthermore, the concrete mixes with CEM I, CEM I + 5 % silica, CEM II/A-LL, CEM II/A-S and CEM I + 30 % slag as binder with entrained air and a water/binder ratio of 0.4 or below, has good resistance to internal and external frost damage. Results show that concrete containing large amounts of slag as part of the binder (CEM III/B) have the severest scaling, irrespective of its content of entrained air.Comparing results from laboratory testing of salt-frost resistance in accordance with SS 13 72 44 (the ‘Slab test’ in CEN/TS 12390-9) with results after nineteen years’ exposure at the highway exposure site shows that the laboratory standard classifies most concrete qualities correctly.However, there is an indication that the laboratory test method may overestimate the scaling resistance of concrete containing a medium to high content of slag as part of the binder. This indicates a need to consider a revision of the slab test procedure so that aging processes is better taken into consideration. A somewhat longer preconditioning time with at least partially an increased carbon dioxide content would for example lead to that the effect of carbonation is better reflected.
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| 4. |
- Eriksson, Daniel, 1987-, et al.
(författare)
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Hygro-thermo-mechanical modeling of partially saturated air-entrained concrete containing dissolved salt and exposed to freeze-thaw cycles
- 2021
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Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846 .- 1873-3948. ; 141
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Tidskriftsartikel (refereegranskat)abstract
- In cold regions, understanding the freeze-thaw behavior of air-entrained concrete is important for designing durable structures and assessing the remaining service life of existing structures. This study presents a hygro-thermo-mechanical multiphase model that describes the cyclic freeze-thaw behavior of partially saturated air-entrained concrete containing dissolved salt. An equilibrium and a non-equilibrium approach are adopted to model the ice formation, including the freeze-thaw hysteresis, inside the porous network. The model also considers the diffusive and convective transport of the dissolved salt coupled to the freeze-thaw processes. Two examples are presented to verify and highlight the capabilities of the model. The first example shows that the model is capable of reproducing the experimentally observed mechanical response of specimens containing NaC1-solutions of different concentrations. In the second example, a larger absorption of liquid from an external reservoir is obtained with an increasing salt concentration in the reservoir, which is consistent with experimental observations.
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| 5. |
- Eriksson, Daniel, 1987-, et al.
(författare)
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Influence of calcium leaching on ice formation in air-entrained concrete: Accelerated experiments and hygro-thermo-mechanical modelling
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Concrete structures in cold regions exposed to long-term contact with soft water often suffer from damage caused by combined calcium leaching and frost actions. This paper experimentally investigates the influence of leaching on the formation and melting of ice inside the pore space of air-entrained concrete. For reference, a non-air-entrained concrete is also tested. An electrochemical accelerated leaching method is adopted to degrade the concrete, and low-temperature calorimetry is used to measure the ice formation. Furthermore, utilising the experimental data, the mechanical response of leached specimens during freeze-thaw exposure is theoretically studied using a hygro-thermo-mechanical multiphase model to explore their coupled effect. The results show a substantial increase in freezable water content that phase changes at relatively small temperature depressions, where the largest increase occurs in air-entrained concrete. The simulation results indicate that the critical degree of saturation becomes lower in leached concrete, hence increasing its susceptibility to frost damage.
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| 6. |
- Eriksson, Daniel, 1987-
(författare)
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Numerical models for degradation of concrete in hydraulic structures due to long-term contact with water
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The durability of concrete is of major concern in all types of concrete structures where the combined effect of exposure conditions and the type and quality of the concrete material usually determines the rate of degradation. Furthermore, there are synergy effects between different deterioration mechanisms, which means that the combined rate of degradation is higher than the sum of the individual rates of each mechanism. Therefore, to accurately predict the residual service life of existing structures or when designing new structures, it is essential to consider all these aspects. This means that various chemical and physical processes, as well as how these interact, must be taken into account in models aiming to be used for service life predictions.This thesis presents the first part of a research project with the aim to investigate common deterioration mechanisms of concrete in hydraulic structures, and to improve the knowledge how these and other related phenomena can be described using mathematical models. The objective is also to study how different mechanisms interact and to find suitable approaches to account for these interactions in the models. To this end, a literature survey on commonly detected damage in hydraulic structures is presented. In addition, it also addresses in what types of and where in hydraulic structures the various damage types are usually observed. The mathematical models presented in this part of the project are focused on long-term water absorption in air-entrained concrete as well as on freezing of partially saturated air-entrained concrete. Both models are based on a multiphase description of concrete and poromechanics to describe the coupled hygro-thermo-mechanical behaviour. The thesis also presents some of the basic concepts of multiphase modelling of porous media, including discretization of the models using the finite element method (FEM). Furthermore, it covers the simplifications that are usually introduced in the general macroscopic balance equations for mass, energy and linear momentum when modelling cement-based materials.To verify the developed models and to show their capabilities, simulation results are compared with experimental data, in situ measurements and other simulations from the literature. The results indicate that both models perform well and can be used to predict long-term moisture conditions in hydraulic structures as well as freezing-induced strains in partially saturated air-entrained concrete, respectively. Even though no interactions with other deterioration mechanisms are included in the models, the development and use of these have given insights to which parameters that are important to consider in such extensions. Furthermore, based on the insights gained, the complexity of describing the full interactions between several mechanisms in mathematical models is also discussed. It is concluded that models aiming to be used for service life predictions of hydraulic structures in day-to-day engineering work need to be simplified. However, the type of advanced models presented in this thesis can serve as a basis to study which aspects and parameters that are essential to consider in simplified prediction models.
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| 7. |
- Fagerlund, Göran, et al.
(författare)
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Studies of the Internal Frost Resistance of HPC
- 1999
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Ingår i: Proceedings of the 6th International Symposium on the Utilization of High Strength/ High Performance Concrete, Sandefjord, Norway, June 1999. - 8291341257 ; 2, s. 1092-1103
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 8. |
- Fridh, Katja, et al.
(författare)
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A model to calculate the CO2-uptake in a country’s concrete structures during service life and after
- 2014
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Ingår i: Nordic Concrete Research. - 0800-6377. ; 50:2, s. 443-446
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Tidskriftsartikel (refereegranskat)abstract
- During the project ‘The CO2-cycle in cement and concrete’ an analytical model to quantify the CO2-uptake in a country a specified year was developed. That was accomplished by deriving a new model for the carbonation process and as input to that, measurements of carbonation in concrete indoors and studies of carbonation in crushed concrete were made. Through knowledge of the cement production each year, the distribution of the cement into different products and estimations of what concrete quality each product has, the total uptake for Sweden was calculated. For the year 2011 was the CO2-uptake calculated to 300 000 tons.
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