Development of low-pH cementitious materials for HLRW repositories

Calvo, José Luis García; Hidalgo, Antonio Vásquez; Alonso, C.; Luco, Luis Fernández

doi:10.1016/j.cemconres.2009.11.008

Cited by 132 publications

(64 citation statements)

References 30 publications

(10 reference statements)

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“…In the case of GGBS negatively charged sulfur species such as sulfide or thiosulfate can additionally decrease the OH -concentrations of the pore solution. The trends in the experimental data are in [2,7,13,25,29,41] line with modelled OH -concentrations for FA and SF blended cements.…”

Section: Discussionmentioning

confidence: 53%

“…Reported experimental data on pore solution composition are collected in a database and variations in composition over time and between systems are statistically evaluated and described. The observed [2,5,7,8,13,15,16,25,28,29,31,33,40,41] trends are compared to calculations of a state-of-theart thermodynamic model for cements blended with increasing amounts of FA and SF. The reviewed experimental data show considerable scatter because of the use of different PCs, SCMs, water to cement ratios and analytical methods.…”

Section: Discussionmentioning

confidence: 99%

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The pore solution of blended cements: a review

et al. 2015

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This paper is the work of working group 3 of the RILEM Technical Committee on Hydration and Microstructure of Concrete with SCM (TC 238-SCM). The pore solution is an essential but often overlooked part of hydrated cements. The composition of the cement pore solution reflects the ongoing hydration processes and determines which solid phases are stable and may precipitate, and which phases are unstable and may dissolve. The study of the cement pore solution therefore contributes to the understanding of the mechanisms as well as of the kinetics of cement hydration. This paper reviews the impact of supplementary cementitious materials (SCMs) on the pore solution composition of blended cements. In a first part, the extraction and analysis methods of cement pore solutions are reviewed, leading to a set of practical guidelines and recommendations. In a second part, an extensive literature survey is used to document the effect of the addition of SCMs (blast furnace slag, fly ash and silica fume) on the pore solution. Finally, in a third part the collected literature data are compared to thermodynamic simulations. The performance and current limitations of thermodynamic modelling of blended cement hydration are demonstrated and discussed in view of future progress.

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Section: Discussionmentioning

confidence: 53%

Section: Discussionmentioning

confidence: 99%

The pore solution of blended cements: a review

et al. 2015

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“…We have developed different concentrations of each chemical as follows: 100%, 75%, 50% and 25% by putting it in 400 ml of each material in the template and we put four bars of steel and leave it and observe the change in the diameters every week, using digital measuring device diameters (caliber). Objective of the protection methods of concrete due to the influence of chemical reactions in this experiment are as follow: (1) to protect the concretefrom the harsh environment and conditions surrounding it, by providing it with an insulating material, which protects the concrete from harmful chemicals (acids or basic) (Garca et al, 2010) (2) to prevent the penetration of these materials in the concrete, (3) to ensure the longest permanence of concrete and (4) to prevent these harmful substances from reaching the reinforcing steel. The materials used for protection are Epoxy and Asphalt.…”

Section: Methodsmentioning

confidence: 99%

Effects of Different Environments on Reinforcement Concrete Corrosion

Awwad¹,

Ahmad²

2017

American Journal of Environmental Sciences

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This research focuses on various forms of steel bar corrosion located in different environments and the factors affecting the corrosion process, both the external (surrounding environment around concrete elements) and the internal environment (concrete itself), as well as on the investigations and tests for this type of damage, in order to develop measurements and recommendations that will reduce harmful investment as much as possible, by increasing the durability and resistance to aggressive environments throughout their life span.The results showed that the concentration (100%-75%) of sulfuric acid decreases more in steel bars diameter than in the second week, but the difference is negligible, and there is no change in the color of precipitation. Concentration (50%-25%) of sulfuric acid also showed decreases in bars diameter than in the second week, but the difference could be omitted, except for the concentration (50%) of sulfuric acid white layer appearance on the steel. In the fourth week, in NAOH, there has been no obvious change in the diameter of steel and an increase was noticed in the deposits substance as well as the appearance of external rust of Steel. HNO 3 with a 25% concentration continued a dramatic corrosion of steel and a large decrease in the diameter of steel was observed, which led to a change in the color of the liquid to brown, due to the fragmentation of steel, and the corrosion of the nonsoaked steel. When exposing the reinforcing bars for acid and base at different concentrations to investigate the ultimate tensile stress, a high decrease in the tensile strength of the steel bar was found, due to the concentration of nitric acid (25-50%) compared to the other acids and base, and this decrease is caused by a high degree of corrosion.

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“…Low pH cementitious materials have been considered to be used in underground repositories for high level waste (HLW), and their microstructural and mechanical properties as well as their resistance against groundwater aggression have been assessed (1)(2)(3)(4)(5)(6)(7). Their development has been addressed from different approaches depending on the type of base cement used.…”

Section: Introductionmentioning

confidence: 99%

“…In both cases, the use of high mineral admixtures contents is mandatory to achieve the required pore fluid pH and also to avoid the microstructural conversion process in the materials based on CAC (3,6,7). These high mineral admixtures contents promote important changes in the microstructural parameters, e.g., in both cases, the resulting cementitious materials mainly consist of calcium silicoaluminate hydrates (C-A-S-H matrixes) with low alumina content in those based on OPC (6,7). As expected, these microstructural changes also promote modifications in the resulting performance parameters (strength gain, final strength value, etc.)…”

Section: Introductionmentioning

confidence: 99%

Shrinkage behaviour and related corrosion performance of low-pH cementitious materials based on OPC or CAC

Calvo¹,

Sánchez²,

Fernández-Luco³

et al. 2016

Mater. construcc.

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Prior to using low-pH cementitious materials in underground repositories for high level waste, the characteristics determining their long-term durability must be analysed in depth. In this sense, different shrinkage tests have been made on mortar and concrete specimens using low-pH cement formulations based on ordinary portland cement (OPC) or calcium aluminate cement (CAC), with high mineral admixtures contents. They showed similar autogenous shrinkage than samples without mineral admixtures but higher drying shrinkage when materials based on OPC with high silica fume contents were considered. Besides, as the use of reinforced concrete could be required in underground repositories, the susceptibility of reinforcement to corrosion when using low-pH cementitious materials based on OPC was analyzed, considering carbon steel and galvanized steel. In the formers corrosion was detected due to the low pore solution pH but any problem was detected when galvanized reinforcement were used. RESUMEN: Fenómenos de retracción y comportamiento frente a la corrosión de materiales base cemento de bajo pH basados en OPC o CAC.Previo al empleo de materiales con cementos de bajo pH en almacenamientos geológicos profundos (AGP) de residuos radiactivos de alta actividad, características relacionadas con su durabilidad a largo plazo deben ser verificadas. Así, su estabilidad volumétrica se ha analizado en morteros y hormigones de bajo pH basados en OPC o CAC, con elevados contenidos de adiciones minerales. Estos presentaron retracciones autógenas similares a las medidas en materiales convencionales, pero retracciones por secado mayores en los basados en OPC y altos contenidos de humo de sílice. Dado que en zonas de los AGP podría emplearse hormigón armado, también se evaluó la susceptibilidad a la corrosión de aceros al carbono y aceros galvanizados en materiales de bajo pH basados en OPC. Se detectó un inicio temprano de corrosión en los primeros debido al bajo pH presente en el fluido de los poros de estos materiales, sin detectarse problemas al emplear aceros galvanizados.

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Development of low-pH cementitious materials for HLRW repositories

Cited by 132 publications

References 30 publications

The pore solution of blended cements: a review

The pore solution of blended cements: a review

Effects of Different Environments on Reinforcement Concrete Corrosion

Shrinkage behaviour and related corrosion performance of low-pH cementitious materials based on OPC or CAC

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