Effect of temperature on porosity and on chloride diffusion in cement pastes

2008 ◽  
Vol 22 (7) ◽  
pp. 1560-1573 ◽  
Author(s):  
Sabine Caré
Keyword(s):  
Chloride Diffusion ◽  
Effect Of Temperature ◽  
Cement Pastes

Pore Structure, Permeability, And Chloride Diffusion In Fly Ash-And Slag-Containing Pastes And Mortars

1988 ◽  
Vol 137 ◽  
Author(s):  
R. I. A. Malek ◽  
D. M. Roy ◽  
Y. Fang
Keyword(s):  
Chloride Diffusion ◽  
Fly Ashes ◽  
Chloride Permeability ◽  
Cement Pastes ◽  
Granulated Blast Furnace Slag ◽  
Transport Of Ions ◽  
Diffusion Rates ◽  
Different Sources ◽  
Limiting Value

AbstractThe transport of ions through cement pastes and mortars with variable contents of fly ashes and granulated blast-furnace slag from different sources and with variable composition has been investigated. The research included the determination of chloride diffusion rate and chloride permeability in relation to microstructure development. The median pore size generally was much diminished in mature blended material compared with Portland cement (PC) pastes and mortars. It appears that, at the same age, a finer microstructure is generally developed in blended specimens compared to PC specimens. Also, it was found that the microstructure approaches a limiting value at longer ages of hydration. That limiting value may be reached at earlier ages with the blends. The chloride diffusion rates and permeabilities in the blends were significantly lower than PC mixes. A comparison between the blends containing fly ashes and those containing slag was made.

scholarly journals Influence of Pore Structure on Chloride Penetration in Cement Pastes Subject to Wetting-Drying Cycles

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Honglei Chang ◽  
Zhiwu Zuo ◽  
Mingyue Qu ◽  
Fei Wang ◽  
Zhi Ge ◽  
...  
Keyword(s):  
Pore Structure ◽  
Penetration Rate ◽  
Error Function ◽  
Chloride Concentration ◽  
Total Porosity ◽  
Chloride Penetration ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Cement Pastes ◽  
The Matrix

Copious studies have discovered a phenomenon that a chloride concentration peak appears on the surface of concrete under cyclic drying-wetting environments. In such cases, the chloride diffusion coefficient (D) obtained through directly fitting the standard error function of Fick’s second law is no longer accurate. The more reliable D obtained by the method proposed by Andrade is employed in this research to investigate the influence of pore structure on chloride penetration rate of pastes. The results show that both the effective coefficient (Deff) and the apparent coefficient (Dapp) increase with total porosity, the most probable pore size, and water absorption porosity, suggesting that the increase of the three pore structure parameters accelerates chloride penetration rate under cyclic wetting-drying condition. The increase of the three parameters makes more room available and eases the difficulty for salt solution to enter the matrix and thus leads to the augmentation of chloride transporting in matrix.

Effect of temperature on the pore solution, microstructure and hydration products of Portland cement pastes

2007 ◽  
Vol 37 (4) ◽  
pp. 483-491 ◽  
Author(s):  
Barbara Lothenbach ◽  
Frank Winnefeld ◽  
Corinne Alder ◽  
Erich Wieland ◽  
Peter Lunk
Keyword(s):  
Portland Cement ◽  
Pore Solution ◽  
Effect Of Temperature ◽  
Hydration Products ◽  
Cement Pastes

scholarly journals Effect of Temperature on Chloride Diffusion in Saturated Concrete

2017 ◽  
Vol 114 (5) ◽  
Author(s):  
B. Touil ◽  
F. Ghomari ◽  
A. Bezzar ◽  
A. Khelidj ◽  
S. Bonnet
Keyword(s):  
Chloride Diffusion ◽  
Effect Of Temperature ◽  
Saturated Concrete

Relationships Between Permeability, Porosity, Diffusion And Microstructure Of Cement Pastes, Mortar, And Concrete At Different Temperatures

1988 ◽  
Vol 137 ◽  
Author(s):  
Della M. Roy
Keyword(s):  
Pore Structure ◽  
Elevated Temperatures ◽  
Mercury Porosimetry ◽  
Blended Cement ◽  
Ionic Species ◽  
Chloride Diffusion ◽  
Concrete Durability ◽  
Chloride Permeability ◽  
Cement Pastes ◽  
Blended Cements

AbstractPermeabilities to water and diffusion of ionic species in cementitious grouts, pastes and mortars are important keys to concrete durability. Investigations have been made of numerous materials containing portland and blended cements, and those with fine-grained filler, at room temperature and after prolonged curing at several elevated temperatures up to 90°C. These constitute part of studies of fundamental material relationships performed in order to address the question of long-term durability. In general, the permeabilities of the materials have been found to be low [many <10−8 Darcy (10−13 m·s−1)] after curing for 28 days or longer at temperatures up to 60°C. The results obtained at 90°C are somewhat more complex. In some sets of studies of blended cement pastes with w/c varying from 0.30 to 0.60 and cured at temperatures up to 90°C the more open-pore structure (at the elevated temperature and higher w/c) as evident from SEM microstructural studies as well as mercury porosimetry are generally correlated also with a higher permeability to liquid. The degree of bonding and permeability evident in paste or mortar/rock interfacial studies present somewhat more conflicting results. The bond strength (tensile mode) has been shown to be improved in some materials with increased temperature. The results of permeability studies of paste/rock couples show examples with similar low permeabilities, and some with increased permeability with temperature.Ionic diffusion studies also bring important bearing to understanding the effect of pore structure. The best interrelationships between chloride diffusion and pore structure appear to relate diffusion rate to median pore size. Similar results were found with “chloride permeability” test.

Effect of Carbonation and Sulphate on Chloride Ingress in Cement Pastes and Concretes with Supplementary Cementitious Materials

2016 ◽  
Vol 711 ◽  
pp. 241-248 ◽  
Author(s):  
Mickael Saillio ◽  
Véronique Baroghel-Bouny ◽  
Sylvain Pradelle
Keyword(s):  
Diffusion Coefficients ◽  
Cementitious Materials ◽  
Chloride Ions ◽  
Supplementary Cementitious Materials ◽  
Chloride Diffusion ◽  
Chloride Ingress ◽  
Chloride Binding ◽  
Cement Pastes ◽  
Binding Isotherms ◽  
In Situ Conditions

The main cause of premature deterioration of reinforced concrete structures is the corrosion of steel bars, induced by chloride ions (for example in marine environment) and/or by carbonation (atmospheric CO2). At the same time, environmental-induced degradations of concrete can also affect the structure, such as sulphate attack. This can lead to the formation of ettringite, inducing expansion inside the materials and finally degradation. Carbonation, chloride and sulphate ingress are usually studied separately in the literature. This is not representative of in-situ conditions since they can occur at the same time and can have an influence on each other. In this paper, chloride ingress are studied for concretes and cement pastes partially carbonated or/and in presence of sulphate in chloride contact solution. The mixtures contain OPC alone or with supplementary cementitious materials (SCM). SCMs are here pozzolanic materials (Fly Ash or Metakaolin) or alkali-activated materials such as ground granulated blast furnace slag (GGBS). The materials, partially carbonated (2 months in chamber at 1.5 % of CO2) or not, are put in contact with chloride solutions in presence of sulphate. This study focuses on the apparent chloride diffusion coefficients, as well as chloride binding isotherms which are obtained by the profile method. In addition, some aspects of the microstructure and of the pore structure are investigated, by using Mercury Intrusion Porosimetry and 27Al NMR, in order to better understand the results obtained relatively to the apparent chloride diffusion coefficients and to the chloride binding. Chloride ingress increases when sulphates are present in the contact solution for all cement materials tested (partially carbonated or not). In addition, chloride ingress is faster when the material is partially carbonated before contact with chloride solution. It appears that both carbonation or presence of sulphate decrease chloride binding, thus explaining the results. The results show an evolution of the properties as a function of the cement replacement ratio by SCMs.

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