| 1. |
- Li, Kefei, et al.
(författare)
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Long-term field exposure of structural concretes in marine environment: state-of-the-art review by RILEM TC 289-DCM
- 2022
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Ingår i: Materials and Structures/Materiaux et Constructions. - : Springer Science and Business Media LLC. - 1359-5997. ; 55:7
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Tidskriftsartikel (refereegranskat)abstract
- This paper reviews the technical aspects related to the long-term field exposure practice in marine environments, based on the return of experiences of major marine exposure sites in world-wide scope. The long-term exposure practice helps both the research on durability mechanisms of structural concretes under real environments and the calibration of durability models to support the life-cycle management of concrete structures. The presentation of the field exposure data can be categorized into the information relevant to exposure sites, the data related to the exposed materials and specimens, the information of environmental actions, and the data related to the performance of materials. A standardized presentation of these data can help the efficiency of data sharing and exploitation. The exploitation of exposure data employs various models to represent the chloride ingress and the induced corrosion risk of the embedded steel bars. There are needs for models addressing the strong environment-material interactions, and simple yet reliable durability indicators for engineering use. The design and operation of exposure stations need the careful choice of exposure sites and specimens, the appropriate scheme for monitoring and inspection of exposed specimens, the systematic recording and management of exposure data, and the regular maintenance of exposure facilities. The support of exposure data for life-cycle management is demonstrated through the durability planning of a real project case. The good practice of long-term field exposure is summarized in the end.
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| 2. |
- Olsson, Nilla, et al.
(författare)
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Moisture transport and sorption in cement based materials containing slag or silica fume
- 2018
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Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 106, s. 23-32
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the moisture dependency of moisture transport and moisture fixation in mortars with OPC, slag and silica fume. Water vapor desorption isotherms were measured with gravimetric methods and the moisture dependency of moisture transport was investigated with cup-tests. The results show an ongoing evolution of water vapor desorption isotherms from eight months to four years. The evolution is more pronounced for mortars containing slag. The results also show that there is a significant difference in moisture dependency of the moisture transport properties above 70% relative humidity; some mortars exhibit a clear moisture dependency in moisture transport whereas others do not. At a relative humidity below 70%, the water to binder ratio is more decisive for moisture transport than the type of binder. These results are of value for service-life models, where they represent important input data, and for understanding the evolution of the microstructure at later ages.
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| 3. |
- Olsson, Nilla, et al.
(författare)
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Non-Saturated Ion Diffusion In Concrete–A New Approach To Evaluate Conductivity Measurements
- 2013
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Ingår i: Cement & Concrete Composites. - : Elsevier BV. - 0958-9465. ; 40, s. 40-47
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Tidskriftsartikel (refereegranskat)abstract
- Non-saturated ion diffusion properties of cementitious materials were evaluated in an experimental study. To assess these properties, resistivity measurements have been performed on mortars with different binders (ordinary Portland cement – OPC, OPC with 5% silica fume, 40% slag and 70% slag, respectively) and different water-to-binder ratios (w/b, 0.38 and 0.53). Specimens have been conditioned to eight different climates with relative humidity (RH) from 100% to 33% RH in order to assess an effective diffusion coefficient. The results from the resistivity measurements have been corrected for changes of the conductivity of the pore solution when drying to different degrees of saturation. The diffusion coefficients for Portland cement binders within the range 100–59% RH are presented.They showed that the diffusion coefficient of the mortar with high w/b ratio was higher at high RH,but at low RH the opposite trend was found. By comparing these results with the corresponding desorption isotherms, it is shown that the diffusion coefficient for the two w/b ratios have the same dependency on the degree of saturation.
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| 4. |
- Olsson, Nilla, et al.
(författare)
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Unsaturated ion diffusion in cementitious materials – The effect of slag and silica fume
- 2018
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Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 108, s. 31-37
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the moisture dependency of ion diffusion in binary cementitious binders with Portland cement (OPC) in combination with slag or silica fume. Resistivity measurements and calculations with a thermodynamic model, GEMS, were used to assess the unsaturated chloride diffusion coefficient. The results show that the relation between the relative diffusion coefficient and the degree of saturation is not significantly affected by w/b (in the investigated range of w/b from 0.38 to 0.53), while the investigated binder compositions seem to affect the relation. These results are of value for service-life models, where they potentially represent important input data. The results also highlight the need for considering the pore solution conductivity when using resistivity measurements for evaluation of ion transport properties.
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| 5. |
- Olsson, Nilla, et al.
(författare)
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Wick action in mature mortars with binary cements containing slag or silica fume – The relation between chloride and moisture transport properties under non-saturated conditions
- 2018
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Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 111, s. 94-103
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Tidskriftsartikel (refereegranskat)abstract
- Moisture and ionic transport under non-saturated condition is an important, but poorly understood transport phenomena particularly for mature systems containing supplementary cementitious materials. This paper investigates the moisture and chloride profiles of 3-year old mortars containing Portland cement (OPC), slag and silica fume (SF) after long-term (30–48 months) wick action exposure in 1.09 M NaCl solution. Moisture profiles were measured with 1H NMR relaxometry and chloride profiles with microXRF. The measured profiles were discussed in relation to moisture dependent material properties such as chloride diffusion coefficients, moisture diffusion coefficients, and desorption isotherms. Results show that the combination of different cementitious materials, e.g. the cementitious binder, is the key factor affecting chloride penetration depth. The cementitious binder also strongly affects chloride diffusion coefficient, moisture diffusion coefficient and chloride binding properties, which are all important parameters for the prediction of chloride ingress.
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