The rim zone of cement-based materials – Barrier or fast lane for chemical degradation?

Schwotzer, Matthias; Konno, Katsuyuki; Kaltenbach, Jonas; Gerdes, Axel

doi:10.1016/j.cemconcomp.2016.10.009

Cited by 5 publications

(3 citation statements)

References 20 publications

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“…This approach opens up new perspectives, in particular, addressing transport properties of the rim zone, which is essential for chemical resilience in aggressive environments. 12 Furthermore, a performance-oriented tuning of the surface chemistry of the compounds of cementitious systems represents an appealing challenge in order to improve the durability without impairing the strength as well as the temperature resistance of the material and counteracting in this way the potential shortcomings of conventional surface protection systems.…”

Section: ■ Introductionmentioning

confidence: 99%

Hydrophobic Properties of Calcium-Silicate Hydrates Doped with Rare-Earth Elements

Burek

Krause

Schwotzer

et al. 2018

ACS Sustainable Chem. Eng.

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In this study, the apparent relationship between the transport process and the surface chemistry of the Calcium-Silicate Hydrate (CSH) phases was investigated. For this purpose, a method was developed to synthesize ultrathin CSH phases to be used as a model substrate with the specific modification of their structure by introducing europium (Eu(III)). The structural and chemical changes during this Eu(III)-doping were observed by means of infrared spectroscopy (IR), Xray photoelectron spectroscopy (XPS), and time-resolved laser fluorescence spectroscopy (TRLFS). These alterations of the CSH phases led to significant changes in the surface chemistry and consequently to considerable variations in the interaction with water, as evidenced by measurements of the contact angles on the modified model substrates. Our results provide the basis for a more profound molecular understanding of reactive transport processes in cement-based systems. Furthermore, these results broaden the perspective of improving the stability of cement-based materials, which are subjected to the impact of aggressive aqueous environments through targeted modifications of the CSH phases.

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Section: ■ Introductionmentioning

confidence: 99%

Hydrophobic Properties of Calcium-Silicate Hydrates Doped with Rare-Earth Elements

Burek

Krause

Schwotzer

et al. 2018

ACS Sustainable Chem. Eng.

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“…The concentration of each component in groundwater derived from seawater is expected to be higher than that in groundwater derived from precipitation, therefore, the number of secondary products is also expected to be higher, corresponding to the solution concentration, suggesting that the effects of clogging may be more significant and inhibit further alterations caused by carbonates and sulfates in the solution. On the other hand, some studies have reported that the ingress of chloride ions and the leaching of cement hydrates were not limited in cases of apparently dense layers formed by the precipitation of secondary products [66]. If the ingress of chloride ions is not limited, the risk of steel corrosion in the disposal facility will be higher because seawater contains a much higher number of chloride ions, and the pore solution pH of cementitious materials is significantly lower due to the reaction with seawater.…”

Section: Influence Of Aqueous Phase Chemistry On Cement Hydrate Alter...mentioning

confidence: 99%

Mineralogical Evolution of High-pH/Low-pH Cement Pastes in Contact with Seawater

Kobayashi,

Sato

2024

Minerals

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In facilities for the geological disposal of radioactive waste in coastal areas, the long-term alteration of cementitious materials in engineered barriers is expected to occur due to the ingress of groundwater derived from seawater. Although the reaction between cement and seawater has been studied, the alteration behavior caused by the reaction between seawater and low-pH cement, which is expected to be used in a disposal facility, has not yet been clarified. In this study, the effects of cement type on cement–seawater interactions were investigated, and the chemical stability and mineral evolution of cement pastes caused by reactions with seawater were determined. The dissolution of cement hydrates occurred upon increased contact with seawater, and the formation of secondary minerals, including carbonate and Mg-containing minerals, was observed. The progress of dissolution depended on the mineral composition of the initially formed cement hydrates, and low-pH cement containing pozzolanic materials showed less resistance to seawater. Differences in pH and Si concentration that are due to the type of cement used had a strong influence on the evolution of minerals (especially Mg-containing minerals), implying that the formed mineral species possibly affect the migration characteristics of radionuclide.

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“…(BROWN e DOERR, 2000;ÇOLAK et al, 2009;SALOMÃO et al, 2010) (SANTHANAM et al, 2003;ALEXANDER et al, 2013;JAKOBSEN et al, 2016). Muitos estudos estão sendo realizados para avaliar o efeito dos cátions associados em ataques ao cimento (principalmente o ataque de sulfatos e cloretos), uma vez que eles podem desempenhar um importante papel no ataque desses dois íons (DE WEERDT et al, 2015;SCHWOTZER et al, 2016).…”

Section: Ataque De íOns Magnésiounclassified

Modelagem descritiva do comportamento do cimento Portland em ambiente de repositório para rejeitos radioativos

Ferreira¹

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The radioactive waste disposal in deep geological repositories has been studied for many countries in the last years. Cementitious materials are used in these repositories as structural material, immobilization matrix and as backfill material. The understanding of the performance of these materials is essential to ensure the safety of the installation during its life time (from thousand to hundreds of thousands of years, depending on the type of waste). This works aims at modeling the long-term performance of Portland cement and study the influence of many environmental factors in the hydration and evolution of this material. The modeling approached the cement hydration in the conditions expected in the repository and the effects of these factors on cement mechanical, mineralogical and morphological properties. The environmental factors considered relevant was: high temperature and pressure, the penetration of groundwater containing aggressive chemical ions, and a radiation field from the waste. Degradation accelerated tests were done to corroborate with the descriptive model. It was observed a synergism between some factors on the cement degradation, as the influence of temperature and radiation field in some deleterious reactions in the material. The results of modeling pointed to three main causes of engineered barrier failure: a) the formation of a preferential pathway; b) loss of resistance and cohesion in the material; and c) the increase in the metallic structures corrosion process. The descriptive model is the basis for a mathematical modeling and to perform the safety assessment of the repositories studied in Brazil

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The rim zone of cement-based materials – Barrier or fast lane for chemical degradation?

Cited by 5 publications

References 20 publications

Hydrophobic Properties of Calcium-Silicate Hydrates Doped with Rare-Earth Elements

Hydrophobic Properties of Calcium-Silicate Hydrates Doped with Rare-Earth Elements

Mineralogical Evolution of High-pH/Low-pH Cement Pastes in Contact with Seawater

Modelagem descritiva do comportamento do cimento Portland em ambiente de repositório para rejeitos radioativos

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