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Détails du magazine
Format
Magazine
eISSN
2545-2819
Première publication
30 Sep 2018
Période de publication
2 fois par an
Langues
Anglais

Chercher

Volume 58 (2018): Edition 1 (June 2018)

Détails du magazine
Format
Magazine
eISSN
2545-2819
Première publication
30 Sep 2018
Période de publication
2 fois par an
Langues
Anglais

Chercher

10 Articles
Accès libre

Long-term Influence of Concrete Surface and Crack Orientation on Self-healing and Ingress in Cracks – Field Observations

Publié en ligne: 01 Dec 2018
Pages: 1 - 16

Résumé

Abstract

This paper presents results from investigations on the long-term influence of concrete surface and crack orientation on ingress in cracks. Five reinforced concrete structures from Norway exposed to either de-icing salts or seawater have been investigated. Concrete cores were taken with and without cracks from surfaces with vertical and horizontal orientation. Carbonation in cracks was found on all de-iced structures, and a crack on a completely horizontal surface appeared to facilitate chloride ingress. Ingress of substances from seawater was found in all cracks from marine exposure. However, the impact of cracks on chloride ingress was unclear. Horizontal cracks on vertical surfaces appeared to facilitate self-healing.

Mots clés

  • Cracks
  • exposure
  • ingress
  • field observations
  • long-term
Accès libre

Reduction of Radon Gas in Concrete Using Admixtures and Additives

Publié en ligne: 01 Dec 2018
Pages: 17 - 34

Résumé

Abstract

The second largest cause of lung cancer is related to radon (222Rn) and its progenies in our environment. Building materials, such as concrete, contribute to the production of radon gas through the natural decay of 238U from its constituents. The Swedish Cement and Concrete Research Institute (CBI) has examined three concrete recipes where only an additive as well as fly ash were added as single constituents to a reference recipe and compared to a reference concrete. The inputs of an additive as well as a supplementary cementitious material (fly ash) were made as a mean to investigate their potential influence on the radon exhalation rates of the concrete. Measurements were performed with an ATMOS 33 ionizing pulsation chamber for at least five different occasions for each recipe during a 22 month period. The results indicate a reduction of the exhalation rate by approximately 30-35 % for each altered recipe. This means roughly 1.5-2 mSv per year decrease in effective dose to a human using an additive or a supplementary cementitious material such as fly ash in relation to the investigated standard concrete.

Mots clés

  • radon
  • effective dose
  • concrete
  • building materials
  • admixtures
  • additives
  • fly ash
  • health
Accès libre

Frost Destruction of Concrete – A Study of the Validity of Different Mechanisms

Publié en ligne: 01 Dec 2018
Pages: 35 - 54

Résumé

Abstract

Well-known frost destruction mechanisms applicable to concrete not exposed to salt are, (1) hydraulic pressure during freezing, (2) growth of ice-bodies in capillaries during freezing. Theories behind these mechanisms are presented. A third mechanism, ice expansion during heating of frozen concrete, is put forward. The validity of a certain mechanisms is discussed by analyzing its ability to explain experimental observations.

Mots clés

  • Frost damage mechanisms
  • hydraulic pressure
  • ice growth
  • thermal deformation
Accès libre

Full-scale Test of an Unreinforced Concrete Dome Plug for the Spent Nuclear Fuel Repository

Publié en ligne: 01 Dec 2018
Pages: 55 - 75

Résumé

Abstract

In the planned Swedish repository for spent nuclear fuel, plugs are designed to close the deposition tunnels. The outer part of these plugs consists of a concrete dome made with self-compacting-concrete, designed to have low pH to reduce negative effects on the bentonite clay buffer. A full-scale test has been performed to evaluate the performance of the plug, to test the installation and to verify underlying design assumptions. In this paper, the behaviour of the concrete dome is evaluated based on measurements, from casting the concrete until it was subjected to 4 MPa hydrostatic water pressure.

Mots clés

  • Nuclear
  • full-scale testing
  • concrete plug
  • shrinkage
  • cooling
Accès libre

The Influence of Supplementary Cementitious Materials on Climate Impact of Concrete Structures Exposed to Chlorides

Publié en ligne: 01 Dec 2018
Pages: 77 - 93

Résumé

Abstract

Addition of fly ash or GGBS in concrete has shown to increase the durability and thus the service life of concrete structures exposed to chlorides. Currently, the durability relies on regulations, which beside a minimum cover thickness also put constraint on amount and type of SCM in different environments. Swedish regulations do not, however, consider the actual durability of different binders. As a consequence, a LCA might be misleading. This paper investigates the climate impact of concrete with SCM in chloride environment. Current prescriptive design approach is compared with a performance based service life approach and applied to bridge parts.

Mots clés

  • chloride induced corrosion
  • Supplementary Cementitious Materials (SCM)
  • climate impact
  • bridge
  • service life
  • LCA
  • concrete
Accès libre

Dynamic Measurements for Determining Poisson’s Ratio of Young Concrete

Publié en ligne: 01 Dec 2018
Pages: 95 - 106

Résumé

Abstract

Knowledge of the elastic properties of concrete at early age is often a pre-requisite for numerical calculations. This paper discusses the use of a laboratory technique for determining Poisson’s ratio at early concrete age. A non-destructive test set-up using the impact resonance method has been tested and evaluated. With the method, it has been possible to obtain results already at 7 hours of concrete age. Poisson’s ratio is found to decrease sharply during the first 24 hours to reach a value of 0.08 and then increase to approximately 0.15 after seven days.

Mots clés

  • Modelling
  • testing
  • Poisson’s ratio
  • young concrete
Accès libre

Filler and Water Reducer Effects on Sedimentation, Bleeding and Zeta-Potential of Cement Paste

Publié en ligne: 01 Dec 2018
Pages: 107 - 125

Résumé

Abstract

Bleeding and sedimentation quantify the stability of fresh cement paste, whereas the addition of fillers and water reducers affect the stability. The effect of various types of fillers and water reducers was investigated by measuring bleeding, hydrostatic pressure and electroacoustic zeta-potential. Depending on their characteristics and use, fillers can improve stability by reducing sedimentation rate and bleeding. The combined effects of fillers and water reducers on the sedimentation rates, quantified as time-dependent hydrostatic pressure changes (dp/dt) in fresh matrix, correspond to their effects on zeta-potentials. The influence of the water reducers on sedimentation and bleeding exceed that of filler type.

Mots clés

  • stability
  • sedimentation
  • bleeding
  • zeta-potential
  • filler
  • water reducer
Accès libre

Continuous Preventive Bridge Maintenance of Swedish Municipalities – A Survey on Common Practice

Publié en ligne: 01 Dec 2018
Pages: 127 - 142

Résumé

Abstract

As part of a report [1] on continuous preventive bridge maintenance, a survey was conducted with Swedish municipalities. The survey’s focus was on bridges and preventive maintenance, as well as the demands and performance control stated by the municipalities. The preventive maintenance the survey focused on was the annual maintenance concerning washing, cleaning of drainage system and removal of vegetation. The survey showed both similarities and differences within the municipalities but also in comparison with Swedish Transport Agency (STA).

Mots clés

  • bridge maintenance
  • preventive maintenance
  • survey
Accès libre

Towards the Understanding of the pH Dependency of the Chloride Binding of Portland Cement Pastes

Publié en ligne: 01 Dec 2018
Pages: 143 - 162

Résumé

Abstract

Hydrated Portland cement paste exposed to a NaCl solution was acidified by adding HCl in small steps, gradually lowering the pH. The chloride binding of the cement paste changed as a function of the pH. For the range of pH from 13.2 to 12.2, decreasing pH resulted in a considerable increase in the chloride binding. At a pH of 11, the cement paste showed almost no chloride binding. In order to explain the changes in chloride binding upon lowering the pH, the phase assemblage was investigated with SEM-EDS, TGA and XRD and compared to a thermodynamic modelling.

Mots clés

  • chloride binding
  • pH
  • C-S-H
  • thermodynamic modelling
  • leaching
Accès libre

Prediction Models for Thermal Conductivity of Cement-based Composites

Publié en ligne: 01 Dec 2018
Pages: 163 - 171

Résumé

Abstract

Cement-based materials are the most consumed materials in the construction industry. Low or high thermal conductive cement-based materials are of interest in applications such as embedded floor heating systems, building envelopes or structural elements. This paper describes prediction models for thermal conductivity of cementitious composites by considering different variables such as constituent materials, porosity and moisture content. The presented prediction models may be used for thermal conductivity based mix design of cementitious materials. Based on the desired accuracy, different solutions are proposed.

Mots clés

  • Mix Design
  • Model
  • Thermal Conductivity
  • Cement-based Materials
10 Articles
Accès libre

Long-term Influence of Concrete Surface and Crack Orientation on Self-healing and Ingress in Cracks – Field Observations

Publié en ligne: 01 Dec 2018
Pages: 1 - 16

Résumé

Abstract

This paper presents results from investigations on the long-term influence of concrete surface and crack orientation on ingress in cracks. Five reinforced concrete structures from Norway exposed to either de-icing salts or seawater have been investigated. Concrete cores were taken with and without cracks from surfaces with vertical and horizontal orientation. Carbonation in cracks was found on all de-iced structures, and a crack on a completely horizontal surface appeared to facilitate chloride ingress. Ingress of substances from seawater was found in all cracks from marine exposure. However, the impact of cracks on chloride ingress was unclear. Horizontal cracks on vertical surfaces appeared to facilitate self-healing.

Mots clés

  • Cracks
  • exposure
  • ingress
  • field observations
  • long-term
Accès libre

Reduction of Radon Gas in Concrete Using Admixtures and Additives

Publié en ligne: 01 Dec 2018
Pages: 17 - 34

Résumé

Abstract

The second largest cause of lung cancer is related to radon (222Rn) and its progenies in our environment. Building materials, such as concrete, contribute to the production of radon gas through the natural decay of 238U from its constituents. The Swedish Cement and Concrete Research Institute (CBI) has examined three concrete recipes where only an additive as well as fly ash were added as single constituents to a reference recipe and compared to a reference concrete. The inputs of an additive as well as a supplementary cementitious material (fly ash) were made as a mean to investigate their potential influence on the radon exhalation rates of the concrete. Measurements were performed with an ATMOS 33 ionizing pulsation chamber for at least five different occasions for each recipe during a 22 month period. The results indicate a reduction of the exhalation rate by approximately 30-35 % for each altered recipe. This means roughly 1.5-2 mSv per year decrease in effective dose to a human using an additive or a supplementary cementitious material such as fly ash in relation to the investigated standard concrete.

Mots clés

  • radon
  • effective dose
  • concrete
  • building materials
  • admixtures
  • additives
  • fly ash
  • health
Accès libre

Frost Destruction of Concrete – A Study of the Validity of Different Mechanisms

Publié en ligne: 01 Dec 2018
Pages: 35 - 54

Résumé

Abstract

Well-known frost destruction mechanisms applicable to concrete not exposed to salt are, (1) hydraulic pressure during freezing, (2) growth of ice-bodies in capillaries during freezing. Theories behind these mechanisms are presented. A third mechanism, ice expansion during heating of frozen concrete, is put forward. The validity of a certain mechanisms is discussed by analyzing its ability to explain experimental observations.

Mots clés

  • Frost damage mechanisms
  • hydraulic pressure
  • ice growth
  • thermal deformation
Accès libre

Full-scale Test of an Unreinforced Concrete Dome Plug for the Spent Nuclear Fuel Repository

Publié en ligne: 01 Dec 2018
Pages: 55 - 75

Résumé

Abstract

In the planned Swedish repository for spent nuclear fuel, plugs are designed to close the deposition tunnels. The outer part of these plugs consists of a concrete dome made with self-compacting-concrete, designed to have low pH to reduce negative effects on the bentonite clay buffer. A full-scale test has been performed to evaluate the performance of the plug, to test the installation and to verify underlying design assumptions. In this paper, the behaviour of the concrete dome is evaluated based on measurements, from casting the concrete until it was subjected to 4 MPa hydrostatic water pressure.

Mots clés

  • Nuclear
  • full-scale testing
  • concrete plug
  • shrinkage
  • cooling
Accès libre

The Influence of Supplementary Cementitious Materials on Climate Impact of Concrete Structures Exposed to Chlorides

Publié en ligne: 01 Dec 2018
Pages: 77 - 93

Résumé

Abstract

Addition of fly ash or GGBS in concrete has shown to increase the durability and thus the service life of concrete structures exposed to chlorides. Currently, the durability relies on regulations, which beside a minimum cover thickness also put constraint on amount and type of SCM in different environments. Swedish regulations do not, however, consider the actual durability of different binders. As a consequence, a LCA might be misleading. This paper investigates the climate impact of concrete with SCM in chloride environment. Current prescriptive design approach is compared with a performance based service life approach and applied to bridge parts.

Mots clés

  • chloride induced corrosion
  • Supplementary Cementitious Materials (SCM)
  • climate impact
  • bridge
  • service life
  • LCA
  • concrete
Accès libre

Dynamic Measurements for Determining Poisson’s Ratio of Young Concrete

Publié en ligne: 01 Dec 2018
Pages: 95 - 106

Résumé

Abstract

Knowledge of the elastic properties of concrete at early age is often a pre-requisite for numerical calculations. This paper discusses the use of a laboratory technique for determining Poisson’s ratio at early concrete age. A non-destructive test set-up using the impact resonance method has been tested and evaluated. With the method, it has been possible to obtain results already at 7 hours of concrete age. Poisson’s ratio is found to decrease sharply during the first 24 hours to reach a value of 0.08 and then increase to approximately 0.15 after seven days.

Mots clés

  • Modelling
  • testing
  • Poisson’s ratio
  • young concrete
Accès libre

Filler and Water Reducer Effects on Sedimentation, Bleeding and Zeta-Potential of Cement Paste

Publié en ligne: 01 Dec 2018
Pages: 107 - 125

Résumé

Abstract

Bleeding and sedimentation quantify the stability of fresh cement paste, whereas the addition of fillers and water reducers affect the stability. The effect of various types of fillers and water reducers was investigated by measuring bleeding, hydrostatic pressure and electroacoustic zeta-potential. Depending on their characteristics and use, fillers can improve stability by reducing sedimentation rate and bleeding. The combined effects of fillers and water reducers on the sedimentation rates, quantified as time-dependent hydrostatic pressure changes (dp/dt) in fresh matrix, correspond to their effects on zeta-potentials. The influence of the water reducers on sedimentation and bleeding exceed that of filler type.

Mots clés

  • stability
  • sedimentation
  • bleeding
  • zeta-potential
  • filler
  • water reducer
Accès libre

Continuous Preventive Bridge Maintenance of Swedish Municipalities – A Survey on Common Practice

Publié en ligne: 01 Dec 2018
Pages: 127 - 142

Résumé

Abstract

As part of a report [1] on continuous preventive bridge maintenance, a survey was conducted with Swedish municipalities. The survey’s focus was on bridges and preventive maintenance, as well as the demands and performance control stated by the municipalities. The preventive maintenance the survey focused on was the annual maintenance concerning washing, cleaning of drainage system and removal of vegetation. The survey showed both similarities and differences within the municipalities but also in comparison with Swedish Transport Agency (STA).

Mots clés

  • bridge maintenance
  • preventive maintenance
  • survey
Accès libre

Towards the Understanding of the pH Dependency of the Chloride Binding of Portland Cement Pastes

Publié en ligne: 01 Dec 2018
Pages: 143 - 162

Résumé

Abstract

Hydrated Portland cement paste exposed to a NaCl solution was acidified by adding HCl in small steps, gradually lowering the pH. The chloride binding of the cement paste changed as a function of the pH. For the range of pH from 13.2 to 12.2, decreasing pH resulted in a considerable increase in the chloride binding. At a pH of 11, the cement paste showed almost no chloride binding. In order to explain the changes in chloride binding upon lowering the pH, the phase assemblage was investigated with SEM-EDS, TGA and XRD and compared to a thermodynamic modelling.

Mots clés

  • chloride binding
  • pH
  • C-S-H
  • thermodynamic modelling
  • leaching
Accès libre

Prediction Models for Thermal Conductivity of Cement-based Composites

Publié en ligne: 01 Dec 2018
Pages: 163 - 171

Résumé

Abstract

Cement-based materials are the most consumed materials in the construction industry. Low or high thermal conductive cement-based materials are of interest in applications such as embedded floor heating systems, building envelopes or structural elements. This paper describes prediction models for thermal conductivity of cementitious composites by considering different variables such as constituent materials, porosity and moisture content. The presented prediction models may be used for thermal conductivity based mix design of cementitious materials. Based on the desired accuracy, different solutions are proposed.

Mots clés

  • Mix Design
  • Model
  • Thermal Conductivity
  • Cement-based Materials

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