Impact of calcium leaching on chloride diffusion behavior of cement pastes exposed to ammonium chloride aqueous solution

The damage process of pure cement pastes with water to cementing material ratios of 0.30, 0.40, 0.50 and 0.60 and fly ash modified pastes with mass fraction of 10%, 30%, 40% and 55% were studied by using ammonium chloride solution with concentrations of 6 mol/l. The total leaching depth, leaching depth, porosity and compressive strength of these pastes leached for 14, 28, 56, 91 and 140 days were tested. The influences of W/C ratio and fly ash content on these properties were analyzed, the relationship between the two factors and the corrosion resistance of pastes was summarized. The results show that the total leaching depth of fly ash modified paste is larger than that of pure cement paste. However, the fly ash modified paste suffers various degree of lowered increment in porosity and strength loss (in percentage) in connection with the added content.

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Impact of calcium leaching on mechanical and physical behaviors of high belite cement pastes

Construction and Building Materials ◽

10.1016/j.conbuildmat.2021.122983 ◽

2021 ◽

Vol 286 ◽

pp. 122983

Author(s):

Chunmeng Jiang ◽

Linhua Jiang ◽

Xinjun Tang ◽

Jingwei Gong ◽

Hongqiang Chu

Keyword(s):

Cement Pastes ◽

Calcium Leaching ◽

Belite Cement

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Notizen:Phosphorescence Decay in Thallium-Doped Ammonium Chloride

Zeitschrift für Naturforschung A ◽

10.1515/zna-1978-1024 ◽

1978 ◽

Vol 33 (10) ◽

pp. 1241-1242 ◽

Cited By ~ 1

Author(s):

S. Chaudhari ◽

T. R. Joshi ◽

R. V. Joshi

Keyword(s):

Aqueous Solution ◽

Ammonium Chloride ◽

Mechanical Treatment ◽

Room Temperature ◽

Host Lattice ◽

Luminescence Decay ◽

Decay Rates ◽

Negative Ion ◽

Ultraviolet Emission ◽

Near Ultraviolet

Abstract The phosphorescence decay rates of thallium-doped ammonium chloride (NH4Cl:Tl) phosphors, prepared by crystallization from aqueous solution, have been studied at room temperature for near-ultraviolet emission. The effects of impurity concentration as well as thermal and/or mechanical treatment on the decay rates have been examined. Phosphorescence centres consisting of a Tl+ion and a nearby negative ion vacancy are suggested to be responsible for the observed luminescence decay. The changes in the decay characteristics after pretreatments are explained on the basis of the location of the centres in normal and distorted regions of the host lattice.

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Influence of Hydrostatic Pressure and Cationic Type on the Diffusion Behavior of Chloride in Concrete

Materials ◽

10.3390/ma14112851 ◽

2021 ◽

Vol 14 (11) ◽

pp. 2851

Author(s):

Huanqiang Liu ◽

Linhua Jiang

Keyword(s):

Diffusion Coefficient ◽

Hydrostatic Pressure ◽

Diffusion Model ◽

Coupling Effect ◽

Experimental Results ◽

Chloride Diffusion ◽

Concrete Durability ◽

Chloride Diffusion Coefficient ◽

Diffusion Behavior ◽

Diffusion Source

The durability of the concrete in underground and marine engineering is affected by the underground and ocean environment. Chloride diffusion coefficient under hydrostatic pressure is a key parameter of concrete durability design under corresponding conditions. Therefore, this paper studies the diffusion behavior of chloride in different diffusion source solutions by experiment and simulation. Based on the experimental results, this paper proposes a new chloride diffusion model under the coupling effect of diffusion and convection. The interaction of ions and compounds in the diffusion source solutions, concrete pore fluid, and concrete material are considered in the new chloride diffusion model. The experimental results show that chloride diffusion rate is significantly affected by hydrostatic pressure, which increases with the increase of hydrostatic pressure. The chloride diffusion coefficient shows a certain difference in difference diffusion source solutions. The chloride diffusion coefficient in divalent cationic diffusion source solutions is the largest, the chloride diffusion coefficient in the divalent and monovalent cationic compound ones is in the middle, and the chloride diffusion coefficient in the monovalent cationic ones is the smallest. There is a linear relationship between the chloride diffusion coefficient and the hydrostatic pressure whether in single or combined cationic diffusion source solutions.

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

MRS Proceedings ◽

10.1557/proc-137-403 ◽

1988 ◽

Vol 137 ◽

Cited By ~ 6

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.

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

Advances in Materials Science and Engineering ◽

10.1155/2019/3909348 ◽

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.

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