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  • 1.
    Babaahmadi, Arezou
    et al.
    RISE - Research Institutes of Sweden, Built Environment, CBI Swedish Cement and Concrete Research Institute. Chalmers University of Technology, Sweden.
    Tang, Luping
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB. Chalmers University of Technology, Sweden.
    Abbas, Zareen
    University of Gothenburg, Sweden.
    Zack, Thomas
    University of Gothenburg, Sweden.
    Mårtensson, Per
    Swedish Nuclear Fuel and Waste Management Company, Sweden.
    Development of an electro-chemical accelerated ageing method for leaching of calcium from cementitious materials2015In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 49, no 1-2, p. 705-718Article in journal (Refereed)
    Abstract [en]

    To facilitate the long term durability predictions of nuclear waste repositories, acceleration methods enhancing calcium leaching process from cementitious materials are needed, even though mechanisms not necessarily comparable to those predominant in a natural leaching process may be developed. In the previously published acceleration methods the samples are very small, which limits further physical or mechanical tests. In this paper, a new acceleration method based on electro-chemical migration is presented. The method although not driven with the same kinetics as in natural leaching, was designed in such a way that unnecessarily destructive by-effects could be minimized while promoting a higher leaching rate for a sample size suitable for further testing the mechanical and physical properties. It is shown that approximately 1 × 106C of electrical charge per paste specimen of size Ø50 × 75 mm (approximately 230 g) is required to leach out the total amount of Portlandite. The chemical and mineralogical properties of leached samples are characterized by various techniques. It is concluded that aged samples are comparable to those leached in a natural leaching process as both are characterized by a layered system comprising an unaltered core delineated by total dissolution of Portlandite followed by a progressive decalcification of the calcium silicate hydrate gel.

  • 2.
    Tang, Luping
    et al.
    Chalmers University of Technology, Sweden.
    Boubitsas, Dimitrios
    RISE - Research Institutes of Sweden, Built Environment, CBI Swedish Cement and Concrete Research Institute.
    Utgenannt, Peter
    RISE - Research Institutes of Sweden, Built Environment, CBI Swedish Cement and Concrete Research Institute.
    Abbas, Zareen
    University of Gothenburg, Sweden.
    Chloride Ingress and Reinforcement Corrosion - After 20 years’ field exposure in a highway environment2018Report (Other academic)
    Abstract [en]

    This report presents the results from a research project financed by Trafikverket, the Swedish Transport Administration, co-financed by Cementa AB.

    In this part of the project work about 35 chloride profiles and ten moisture profiles have been measured from various types of concrete specimens exposed to a de-icing salt highway environment for about 20 years. The non-destructive technique, RapiCor, for corrosion measurement was used to assess the conditions of steel embedded in concrete beams with different types of binder and water-binder ratios. The ClinConc model were used to predict chloride ingress in concrete. Some laboratory test methods and numerical simulations were carried out to study the behaviour of concrete after long-term exposure.

    The results show that chloride ingress profiles measured after 2

    0 years’ exposure under the de-icing salt highway environment are in general lower than those measured after the similar exposure duration under the marine splash environment.

    Non-destructive corrosion measurement by RapiCor instrument is in general in reasonably good agreement with chloride ingress. The corrosion rust observed from the destructive examination verified again that the non-destructive technique RapiCor is a useful tool for detection of ongoing corrosion of steel in concrete.

    The ClinConc model in general gives reasonably good prediction of chloride ingress front in the bulk concrete but not in the near surface zone due to the drying-wetting cycles in the highway environment. After a certain modification with the consideration of redistribution of bound chloride in the near surface zone, the model can reasonably well describe the chloride ingress profiles measured from the exposure site.

  • 3.
    Tang, Luping
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB, Hållbara byggnadsverk. Chalmers University of Technology, Sweden.
    Utgenannt, Peter
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB.
    Boubitsas, Dimitrios
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB, Betong & Berg.
    Durability and service life prediction of reinforced concrete structures2015In: Journal of the Chinese Ceramic Society, ISSN 0454-5648, Vol. 43, no 10, p. 1408-1419Article in journal (Refereed)
    Abstract [en]

    This paper presents some durability and service life models for reinforced concrete structures with regard to chloride ingress, carbonation and frost attack. In the past years a number of models for durability design of concrete structures have been suggested by relevant organisations or international committees. It is necessary to validate these models against long-term field data for their applicability with respect to exposure climate in order to satisfactorily use the models in the durability design and redesign of concrete structures. In this study, various potential models for concrete resistance to chloride ingress, carbonation and frost attack were briefly reviewed. Three models including the simple ERFC, the DuraCrete and the ClinConc, for prediction of chloride ingress were evaluated using the infield data collected from both the field exposure site after over 20 years exposure and the real road bridges of about 30 years old. A physicochemical model for prediction of carbonation depth was evaluated using the infield data collected from the field exposure site after 11 years exposure and the limited data from the real structures with the age of 7-13 years. For the modelling of frost attack, some problems in measurement of critical saturation degree and actual degree of saturation are discussed. According to the comparison results, the simple ERFC overestimates whilst the DuraCrete model underestimate the chloride ingress in most cases. The ClinConc model on the other hand gives reasonable good prediction for both the short-term (one year) and the long-term (21 years) exposure. The Papadakis model for carbonation also gives fairly good prediction of carbonation depth when compared with the Norwegian infield data classified as exposure class XC3|, but underestimates the carbonation depths when compared with the infield data from Norwegian structures in exposure class XC4.

  • 4.
    Zhang, Emma Qingnan
    et al.
    Chalmers University of Technology, Sweden.
    Tang, Luping
    RISE, SP – Sveriges Tekniska Forskningsinstitut, CBI Betonginstitutet AB, Hållbara byggnadsverk. Chalmers University of Technology, Sweden.
    Zack, Thomas
    University of Gothenburg, Sweden.
    Carbon fiber as anode material for cathodic prevention in cementitious materials2016In: International Conference on Durability of Concrete Structures (ICDCS 2016), Purdue University Press, 2016, p. 300-308Conference paper (Refereed)
    Abstract [en]

    Cathodic prevention (CPre) technique is a promising method and has been used for the past two decades to prevent steel from corrosion in concrete structures. However, wide application of this technique has been restricted due to high costs of anode materials. In order to lower the cost and further improve this technique, carbon fiber composite anode has been introduced as an alternative anode material with affordable price and other outstanding properties. This paper presents the study of using carbon fiber mesh as anode material for long-term cathodic prevention system and the effect of accelerated current on macro- And microstructure of cementitious materials. In the study, electrochemically accelerated tests were developed for the purpose of shortening the experimental time into a manageable range. An estimation tool was used to predict the service life as well. Chemical and microstructure analyses were carried out by laser-ablation inductively-coupled-plasma mass-spectroscopy (LA-ICP-MS) and scanning electron microscope (SEM). Results indicate that calcium to silicon (Ca/Si) ratio and ion re-distribution in the current-affected zone around the anode were changed due to migration and electrochemical reactions. The predicted service life was in general longer than 100 years. Based on the results from this work, it can be concluded that carbon fiber mesh is suitable for the application as anode in long-term cathodic prevention system in cementitious materials.

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