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 Août 2014

 

Atmopsheric corrosion of reinforced concrete steel in tropical coastal regions : in Engineering Journal, vol. 17, n° 2  / Castaneda, Abel ; Corvo, Francisco ; Howland, Juan José ; Perez, Tezozomoc . – 2013. En ligne
Résumé : The influence of atmospheric parameters and chloride deposition rate on concrete using an atmospheric corrosion approach is rarely found in literature. Seven exposure sites were selected in Havana, Cuba and two at Yucatan Peninsula, Mexico, to expose reinforced concrete samples. Two significantly different atmospheric corrosivity levels have been observed after two years of exposure in Havana depending on atmospheric chloride deposition and the w/c ratio of the concretes. Changes in corrosion current are in accordance with changes in chloride penetration and atmospheric chloride deposition. The influence of sulphur compounds deposition should be considered to study atmospheric corrosion of reinforced steel in foncretes either in Havana.
béton armé
chlorure
corrosion
eau / ciment
environnement marin
environnement tropical
Golfe du Mexique, condition environnementale.

Carbonation of concretes in the Mexican Gulf : in Building and Environment, 35  / Castro, P. ; Sanjuán, Miguel Angel ; Genescá, J. . – 2000. – pp. 145-149. En ligne
Résumé : Carbon dioxide penetration into concrete leads to reinforcing depassivation and onset of the corrosion process. Thus, a deep knowledge on the parameters a€ecting such a process will allow definition of the most suitable mixture design to provide adequate durability. Experimental results show the e€ect of an exposed location in a coastal area on the carbonation process of ®ve qualities of concrete. The carbonation depth was checked by spraying phenolphthalein. The results generally showed that the more distance from the coast, the greater the carbonation rate. The results also showed the greater the strength, the lower the carbonation coecient when specimens are located at 50 m from the seaside. Whereas, in those located at 100 m and 780 m, such a trend is unclear for concretes of 28-day compressive strength higher than 22 MPa. # 1999 Elsevier Science Ltd. All rights reserved.
béton
carbonatation
environnement tropical
Golfe du Mexique, condition environnementale

Concrete durability presented by acceptable chloride level and chloride diffusion coefficient in concrete: 10-year results in marine site / Cheewaket, T. ; Jaturapitakkul, C. ; Chalee, W.
in Materials and Structures volume 47, n° 9 (septembre 2014). – pp. 1501-1511 En ligne
Résumé: Generally, concrete with high resistance to the marine environment should have high compressive strength, a low chloride diffusion coefficient (D C), and a high acceptable chloride level (Ac). Considering all parameters simultaneously, this study evaluated the degree of fly ash concrete durability based on 10-year results in a marine site. Based on the concrete durability (Ac/D C, as compared to cement concrete with a W/B ratio of 0.45) and compressive strength, the degree of concrete durability proposed in this study indicates that fly ash concretes with a W/B ratio of 0.45 and 15–35 wt % fly ash replacement exhibit high-quality performance in a marine site.
cendre volante
coefficient diffusion chlorure
durabilité
environnement marin
ouvrage maritime

Potential measurement to determine the chloride threshold concentration that initiates corrosion of reinforcing steel bar in slag concretes / Garcia, Vincent ; François, Raoul ; Carcassès, M. ; Gégout, Philippe   in Materials and Structures volume 47, n° 9 (septembre 2014). – pp. 1483-1499 En ligne
Résumé: The chloride content at which reinforcement corrosion occurs (Ccrit) is an important parameter for the determination of the service life of a concrete structure. Many studies have been conducted on Portland cement concrete but few data are available concerning slag concrete. In this study, a method for determining the Ccrit value is proposed. It uses capillary suction and a diffusion phase with steel-potential monitoring during the progressive contamination of the concrete by chloride. The same experimental process, capillary suction then diffusion, was performed simultaneously with tap water and chloride solution to verify the specific behaviour of specimens due to the presence of chloride. During the phase of diffusion and potential monitoring, samples were kept immersed in saturated conditions. The criterion for detecting corrosion initiation was a variation of about –250 mV (Ghods et al., Corrosion Science 52:1649–1659, 2010), which corresponds to the difference usually noted between steel in the passive and active state. Two concrete compositions were investigated: one with only Portland cement as the binder and one incorporating slag with a substitution level of 60 %. As expected, in the Portland cement concrete, a drop in potential occurred when corrosion started. For slag concrete, no potential drop was recorded because the initial potential of the steel before the introduction of chlorides was lower. The method for determining Ccrit, based on the fall in potential recorded when corrosion started, would not be suitable to compare the different compositions of binder in saturated conditions. The presence of sulphides in the pore water solution of the slag concrete is a possible explanation of this result. Tests in a solution with added sulphides tended to confirm this hypothesis.
amorçage de corrosion
ciment laitier
ciment Portland
corrosion
seuil de concentration critique (chlorure)

Set-on-demand concrete / Duddukuri Nair, Sriramaya ; Ferron, Raissa Douglas   in Cement and Concrete Research volume 57 (mars 2014). – Pages 13-27. En ligne
Résumé: The ability to control the fresh-state properties of concrete in real-time provides the user greater control over processing and placing of concrete. Based on the principles of magnetorheology, a smart cement-based material system has been developed wherein magnetic particles are added and an external magnetic field is applied to control the fresh-state properties of concrete. Rheological tests were conducted on paste mixtures containing magnetic particles and when a magnetic field was applied, it was determined that the shear resistance of the paste could be altered significantly. The response of the paste was found to be dependent on the magnetic field strength and the concentration of the magnetic particles. Furthermore the magnetic particles used did not have any effect on cement hydration products or on compressive strength results. Such a material can be useful in applications in which controlling the fresh-state behavior of concrete is critical.
béton frais
hydratation
pâte ciment
propriété magnétique
résistance compression
rhéologie

Engineering performance of a new siloxane-based corrosion inhibitor / Holmes, N. ; O’Brien, R. ; Basheer, P. A. M.   in Materials and Structures volume 47, n° 9 (septembre 2014). En ligne
Résumé: This paper presents an evaluation of a new non-toxic corrosion inhibitor on selected engineering properties of concrete mixes with different cementitious materials following a corrosion and durability study on concrete samples. Corrosion inhibitors consist of powders or solutions which are added to concrete when mixed to prevent or delay corrosion of steel by their reaction with ferrous ions to form a stable and passive ferric oxide film on the steel surface. The new inhibitor functions slightly differently and its corrosion inhibition effect is due to the formation of a siloxane coating on the steel surface. Therefore, the performance of the new inhibitor in concrete mixes manufactured with CEM I, PFA and GGBS cements was compared against a well known and established corrosion inhibitor on the market, namely calcium nitrite in terms of their effect on workability (measured in terms of slump), compressive strength, freeze–thaw durability and macro-cell corrosion. The results from this experimental programme have demonstrated that the new inhibitor is effective in reducing or slowing down corrosion. In addition, it was found that CEM I concrete containing the new inhibitor was less penetrable to chlorides than that without. A similar set of results was obtained for the freeze–thaw resistance, but the compressive strength was found to decrease with the addition of the new inhibitor. In the case of concretes containing PFA and GGBS, the new inhibitor was found to be less effective. Further, long-term investigations are recommended to assess the effectiveness over time.
durabilité
inhibiteur corrosion
nitrite de calcium
siloxane

Effectiveness of the accelerated mortar bar test to detect rapid reactive aggregates (including their pessimum content) and slowly reactive aggregates / Alaejos, P. ;Lanza, V. ; Bermúdez, M. A. ; Velasco, A.   in Cement and Concrete Research volume 58 (avril 2014). – Pages 13-19. En ligne
Résumé: The accelerated mortar bar test (AMBT) is one of the most common tests to detect reactive aggregates although it has some limitations: there is no agreement on the limit of expansion, fails appear when testing slowly reactive aggregates and a laborious work is needed to find the pessimum content.

An experimental programme on the AMBT has been carried out to overcome these limitations. Rapid and slowly reactive aggregates extracted from real Spanish structures affected by alkali silica reaction have been used. As a result, the test detected correctly all the reactive aggregates, but with the following requirements: a limit of 0.10% at 14 days for rapid reactive aggregates and 0.20% at 90 days for slowly reactive aggregates.

Also the pessimum content has been found between 5 and 15 vol% of equivalent reactive quartz, giving a peak expansion of 0.42% (14 days). The expansion after this peak decreased but it was always over 0.10%.
alcali-réaction
mortier
pétrographie
réaction alcali-granulat

Ciments

MgO expansive cement and concrete in China: Past, present and future / Mo, Liwu ; Min, Deng ; Tang, Mingshu ; Al Tabbaa, A.   in Cement and Concrete Research volume 57 (mars 2014). – Pages 1-12. En ligne
Résumé: Uniquely, China employs MgO already contained in cement clinker or as an expansive additive to compensate for the thermal shrinkage of mass concrete, particularly dam concrete, with almost 40 years’ experience in both research activities and industrial applications. Compensating shrinkage with expansion produced by MgO has been proved to effectively prevent thermal cracking of mass concrete, and reduce the cost of temperature control measures and speed up the construction process. Moreover, the expansion properties of MgO could be designed flexibly, through adjusting its microstructure by changing the calcination conditions (calcining temperature and residence time). The collective knowledge and experience of MgO expansive cement and concrete is worthy of sharing with relevant engineers and researchers globally but dissemination has been hindered as most of the relevant literature is published in Chinese. This paper reviews the history, state-of-the-art progress and future research needs in the field of MgO expansive cement and concrete.
caractérisation
ciment expansif
expansion
hydratation
oxyde de magnesium
retrait empêché

On the physico-chemical evolution of low-pH and CEM I cement pastes interacting with Callovo-Oxfordian pore water under its in situ CO2 partial pressure / Dauzeres, A. ;Le Bescop, P. ; Cau-dit-Coumes, C. ; Brunet, Fabrice ; Bourbon, X. ; Timoen, J. ; Voutilainen, M. ; Chomat, L. ; Sardini, P.   in Cement and Concrete Research volume 58 (avril 2014). – Pages 76-88. En ligne
Résumé: Within the framework of geological repositories for radioactive waste, structural concretes must be adapted to the underground chemical conditions. CEM I cement-based materials are characterised by high pH that may produce an alkaline plume in the near-field of the repository. In order to avoid this problem, low-pH cements have been designed. This study compares the physico-chemical behaviour of a low-pH material with a CEM I cement paste, both being subjected to leaching by an aqueous solution. An original experimental setup was designed to reproduce the underground conditions using a specific CO2 regulation device. Under these conditions, the low-pH material was strongly degraded, which results in coarser porosity, whereas thickness degradation of the CEM I cement paste is limited by the precipitation of a magnesium-calcite crust over the surface, which reduces the exchange of soluble species. This paper also presents a new approach for microstructure characterisation based on high-resolution X-ray microtomography.
argile / béton
barrière argile
carbonatation
durabilité
liant bas pH
microstructure
pâte ciment
stockage profond, déchet radioactif

Preparation of magnesium phosphate cement by recycling the product of thermal transformation of asbestos containing wastes / Viani, Alberto ; Gualtieri, Alessandra F.   in Cement and Concrete Research volume 58 (avril 2014). – Pages 56-66. En ligne
Résumé: Asbestos containing wastes have been employed for the first time in the formulation of magnesium phosphate cements. Two samples were mixed with magnesium carbonate and calcined at 1100 and 1300 °C. Under these conditions, complete destruction of asbestos minerals is known to occur. The product, containing MgO, after reaction with water-soluble potassium di-hydrogen phosphate, led to the formation of hydrated phases at room temperature. Crystalline and amorphous reaction products were detected, with the latter being likely the metastable precursor of the former. Measured strengths were found to be in line with data from the literature, suggesting that this material may be used as cement. The process here described represents a viable recycling opportunity for this class of hazardous wastes. Simultaneous destruction of asbestos minerals and formation of reactive MgO during thermal treatment, bring benefits in terms of energy requirements and preservation of natural resources in cement manufacturing.
amiante ciment
déchet de déconstruction, recyclage
liant phosphomagnésien

Use of glass waste as an activator in the preparation of alkali-activated slag. Mechanical strength and paste characterisation / Puertas, F. ; Fernandez-Carrasco, L.   in Cement and Concrete Research volume 57 (mars 2014). – Pages 95-104. En ligne
Résumé: The alkaline activation of aluminosilicates yields alkaline cements, eco-efficient alternatives to ordinary Portland cements. Alkaline cements and concretes exhibit highest strength and longest durability when activated with a solution of alkaline silicate hydrates (waterglass). To obtain these alkaline silicates, however, an aqueous solution of the proper proportion of carbonate and silica salts must be heated to temperatures of around 1300 °C. The present paper explores the feasibility of using urban and industrial glass waste as a potential alkaline activator for blast furnace slag (AAS).

AAS pastes were prepared with three activators: waterglass, a NaOH/Na2CO3 mix and the solutions resulting from dissolving glass waste in NaOH/Na2CO3. Mechanical, mineralogical (XRD, FTIR) and microstructural (porosimetry, NMR and SEM/EDX) trials were conducted to characterise the pastes obtained.

The findings proved the feasibility of using glass waste to alkali activate slag. Treating glass waste with NaOH/Na2CO3 (pH = 13.6) favours the partial dissolution of the Si in the glass into its most reactive monomeric form.

The solutions resulting from the treatment of glass waste act as alkaline activators, partially dissolving vitreous blast furnace slag. The composition and microstructure of the reaction products identified in the two types of paste were similar. Strength and microstructural development in the pastes activated with glass waste were also comparable to the parameters observed in AAS pastes prepared with conventional activators.
activation alcaline
caractérisation
ciment laitier
résistance mécanique
verre, recyclage

Granulats de béton recyclé

Cement paste content and water absorption of recycled concrete coarse aggregates / Belin, P. ; Habert, Guillaume ; Thiéry, Mickaël ; Roussel, Nicolas   in Materials and Structures volume 47, n° 9 (septembre 2014). – pp. 1451-1465. En ligne
Résumé: In this paper, we first show that the amount of residual cement paste in recycled concrete aggregates (RCA) depends on the initial paste content, on the mechanical properties of the initial cement paste and on the mechanical quality of the transition zone at the interface between the initial natural aggregates and cement paste. Our results suggest that water absorption of RCA at 24 h can be seen as the simple sum of the capillary absorption of both residual cement paste and initial natural aggregates. The absorption kinetics is similar to the capillary absorption of traditional uncrushed concretes but, on the industrial time scale of interest, is strongly affected by the size and configuration of the residual cement paste patches at the surface of the initial natural aggregates. We finally propose a tentative frame for a classification of RCA based on water absorption rate and water absorption capacity at 24 h.
absorption eau
granulat de béton recyclé
maniabilité

 

Etude bibliographique sur la valorisation des sédiments de dragage marins traités aux liants hydrauliques en technique routière : Rapport technique 1  / Boutouil, Mohammed ; Saussaye, Lucile ; Maherzi, W. ; Ben Abdelghani, F. . – ESITC, 2011. – 34 p. En ligne
Résumé : Ce premier rapport technique doit établir la synthèse de données bibliographiques sur les filières actuelles d’utilisation des sédiments de dragage marins ainsi que sur leur potentiel de valorisation dans le domaine de la construction routière.
Dans un premier temps l’évolution de la législation relative aux opérations de dragage est établie afin de montrer les restrictions qu’elle génère et les besoins de démontrer la possibilité de réutilisation de tels matériaux. Les sédiments de dragage marins fins sont ensuite définis suivants leurs principaux paramètres physiques et géotechniques.
La troisième partie est ciblée sur les méthodes de valorisation de sédiments en techniques routières. Cette partie oriente particulièrement les choix du travail expérimental qui sera mené dans le cadre du projet SETARMS.
caractérisation
microstructure
minéralogie
pollution
propriété mécanique
sédiment marin
sédiment, valorisation
traitement chaux

Caractérisation géotechnique des sédiments bruts et introduction à l’électrocinétique : Rapport technique 2  / Boutouil, Mohammed ; Saussaye, Lucile ; Maherzi, W. ; Ben Abdelghani, F. . – ESITC, 2011. – 42 p. Accompagne   Etude bibliographique sur la valorisation des sédiments de dragage marins traités aux liants hydrauliques en technique routière / Boutouil, Mohammed. En ligne

Résumé : Ce premier rapport technique doit établir la synthèse de données bibliographiques sur les filières actuelles d’utilisation des sédiments de dragage marins ainsi que sur leur potentiel de valorisation dans le domaine de la construction routière.
Dans un premier temps l’évolution de la législation relative aux opérations de dragage est établie afin de montrer les restrictions qu’elle génère et les besoins de démontrer la possibilité de réutilisation de tels matériaux. Les sédiments de dragage marins fins sont ensuite définis suivants leurs principaux paramètres physiques et géotechniques.
La troisième partie est ciblée sur les méthodes de valorisation de sédiments en techniques routières. Cette partie oriente particulièrement les choix du travail expérimental qui sera mené dans le cadre du projet SETARMS.
caractérisation
microstructure
minéralogie
pollution
propriété mécanique
sédiment marin
sédiment, valorisation
traitement chaux

 

Conservations des sites et du mobilier archéologiques : Etudes et documents sur le patrimoine culturel . – UNESCO, 1987. – 114 p. En ligne
archéologie
conservation
mosaïque, conservation
moulage
pierre, conservation
polychromie

Catalogue d’éléments de construction avec calcul de la valeur U. Construction neuve . – Office fédéral de l’énergie (Suisse), 2002. – 76 p. En ligne
Résumé : Le coefficient de transmission thermique U – plus simplement nommé valeur U et auparavant valeur k – est l’un des paramètres les plus importants du calcul de l’isolation thermique des bâtiments.
Dans la partie générale, on s’attache à définir la valeur U et à montrer quels sont les facteurs qui peuvent l’influencer. Cette partie donne également un aperçu de la méthode que l’on applique pour déterminer la valeur U des éléments neufs.
Le chapitre suivant présente au lecteur les principes et la méthode de calcul de la valeur U, puis démontre, à l’aide de divers exemples et exercices, comment la déterminer. Le chapitre intitulé «Catalogue d’éléments de construction » est un ouvrage de référence contenant les éléments rencontrés le plus fréquemment dans la pratique ; il permet aux utilisateurs de déterminer ou de contrôler la valeur U d’un élément sans devoir recourir au calcul. Des indications concernant les fenêtres et les portes y ont aussi été intégrées. Ce chapitre remplace la Fiche technique «Valeurs k et valeurs g des fenêtres» de l’Office fédéral de l’énergie.
On trouvera à la fin de la publication les aides complémentaires suivantes:
Tableau A: Calcul des valeurs U – Tableau B: Détermination des valeurs U à l’aide du Catalogue d’éléments de construction – Tableau Aw: Calcul des valeurs U des fenêtres Ils peuvent être reproduits et remis à titre de justificatif aux autorités compétentes.
Note de contenu : Le tableau PP. 12 et 13 indique la conductivité thermique de différents matériaux de construction, dont le béton, différents mortiers, les pierres naturelles, les briques, etc…
coefficient de diffusion
conductivité thermique
isolation thermique
matériau
pont thermique