| 1. |
- Babaahmadi, Arezou, 1985, et al.
(författare)
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Ageing process of cementitious materials: Ion transport and diffusion coefficient
- 2012
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Ingår i: Concrete Repair, Rehabilitation and Retrofitting III - Proceedings of the 3rd International Conference on Concrete Repair, Rehabilitation and Retrofitting, ICCRRR 2012. - 9780415899529 ; , s. 369-374
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Konferensbidrag (refereegranskat)abstract
- Risk assessment analysis concerning service life predictions of concrete structures in nuclear waste repositories requires broad knowledge about long-term concrete deterioration processes. It is well known that the degradation process of cementitious materials involves diffusion of internal and external ions, interaction between these ions and re-deposition of the interacted products. However, although diffusion properties play an important role in the deterioration process, there is a lack of reliable data on ion diffusivity in concrete, especially co-existing ions rather than chloride. The aim of this study is to further analyze multi-component ionic diffusion accompanied with surface complexation and selective adsorption. Natural diffusion cell and field immersion tests are used to analyze transport properties of ions present in groundwater surrounding nuclear waste repositories such as chloride, sodium, lithium and calcium ions, through cement paste. Analytical techniques such as Ion chromatography, potentiometric titration, inductively coupled plasma mass spectrometry and X-ray fluorescence methods are used. Results indicate that the ionic diffusion coefficients differ between different ions and the higher the concentration of the ions, the lower the diffusion coefficient will be.
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| 2. |
- Garcia, A., et al.
(författare)
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Influence of cement content and environmental humidity on cement-asphalt composites performance
- 2012
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Ingår i: Concrete Repair, Rehabilitation and Retrofitting III - Proceedings of the 3rd International Conference on Concrete Repair, Rehabilitation and Retrofitting, ICCRRR 2012. - 9780415899529 ; , s. 247-253
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Konferensbidrag (refereegranskat)abstract
- Ideally, a material with low-environmental impact and combining the advantages of both asphalt and concrete could be obtained by combining bitumen emulsions and a cementitious material. These bitumen emulsions harden by a process where the water in the mixture is removed both by evaporation and by cement hydration. In this research, cold asphalt mixtures with different percentages of cement replacement have been prepared and tested with Marshall Stability tests. Furthermore, mixtures with 0% and with 3% of cement replacement were cured under different environmental relative humidity (35, 70 and 90% RH). Additionally, the mass evolution of the specimens cured under different humidity conditions was measured. According to the results of the present study, cement contributes to the hardening of cold asphalt mixtures by creating mortar bridges between the aggregates and by removing water from the mixtures through cement hydration.
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| 3. |
- Rosenqvist, Martin, et al.
(författare)
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Macroscopic ice lens growth : observations on Swedish concrete dams
- 2012
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Ingår i: Concrete Repair, Rehabilitation and Retrofitting III. - 9780415899529 - 9780203124253 ; , s. 658-664
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Konferensbidrag (refereegranskat)abstract
- The arch dam at Selsforsen and the buttress dam at Storfinnforsen are two concrete dams of which both have suffered from severe surface spalling on the upstream face, far below the full water supply level. A hypothesis is that macroscopic ice lens growth, similar to frost heave in soil, could have occurred within the dam walls. After initial deterioration of the concrete dams by frost damage or cracking, the formation of macroscopic ice lenses could have been made possible. In an attempt to test the hypothesis, specimens of low strength concrete were exposed in the laboratory to climatic boundary conditions similar to those of the dams. After one week of freezing, the upper part of the concrete specimens was separated from the lower part due to cracking. The gradual propagation of the crack, which appeared about 25 mm below the top surface, was caused by macroscopic ice lens growth.
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| 4. |
- Sederholm, Bror, et al.
(författare)
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Cathodic protection of concrete structures with thermally sprayed sacrificial zinc anodes - Critical parameters for the protective ability of the sprayed-on anode
- 2012
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Ingår i: Concrete Repair, Rehabilitation and Retrofitting III - Proceedings of the 3rd International Conference on Concrete Repair, Rehabilitation and Retrofitting, ICCRRR 2012. - 9780415899529 ; , s. 978-984
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Konferensbidrag (refereegranskat)abstract
- This paper presents an ongoing project regarding Cathodic protection of concrete structures with thermally sprayed sacrificial zinc anodes. The project is divided into two parts: Stage 1 shows the results from a survey of literature and practical experiences of the use of cathodic protection of concrete structures with sprayed zinc sacrificial anodes. Results from investigations of thermally zinc sprayed concrete structures such as concrete walls in the water intake building on a nuclear plant and on the edge beam of the Öland Bridge are presented in the paper. Stage 2 in the project is focused on the critical parameters for the protective ability of the sprayed-on anode. A laboratory setup and a field object are presented as well as the methods used to evaluate the sprayed-on anode. The present investigations show that the resistivity of the concrete has a great influence on the protective ability of the sprayed-on anode. Further, the life length of the zinc anode depends on the external environmental conditions at the anode. In conclusion it can be stated that the prospect of using cathodic protection with thermally sprayed zinc sacrificial anodes is promising but in order to optimize the use, threshold values need to be determined regarding for example the humidity, carbonation depth and the chloride content of the concrete.
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