Alkali Ion Concentration Estimations in Cement Paste Pore Solutions

Sanjuán, Miguel Ángel; Estévez, Esteban; Argiz, Cristina

doi:10.3390/app9050992

Cited by 7 publications

(5 citation statements)

References 25 publications

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“…Indeed, Equation (1) represents a simplified approach to calculating the OH − ion concentration in the pore solution of Portland cement concrete. This equation assumes the total and prompt dissolution of cement alkalis and does not take into account: (1) The alkali uptake by the cement hydration products, especially calcium silicate hydrate (C-S-H gel) and, to a minor extent, calcium alumina-silicate hydrate (C-A-S-H) and monosulphate phase (AF m ) [31][32][33][34][35] and (2) the consumption of effective water by cement hydration.…”

Section: Factors Affecting Pore Liquid Alkalinitymentioning

confidence: 99%

“…The distinction between the various forms of alkalis (water-soluble and total alkalis) contributing to the pore solution alkalinity may only be useful to differentiate the OH − ion concentrations in the pore liquid during the early and mature phases of Portland cement hydration, especially in the case of Portland cements very rich in water-soluble alkalis [35].…”

Section: Factors Affecting Pore Liquid Alkalinitymentioning

confidence: 99%

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Assessment of Alkali–Silica Reactivity of Aggregates by Concrete Expansion Tests in Alkaline Solutions at 38 °C

et al. 2020

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A new accelerated concrete prism expansion test at 38 °C (accelerated CPT) is proposed for assessing the alkali-reactivity of concrete aggregates. In this test, concrete prisms with a standardized mix composition and different alkali contents are immersed in alkaline solutions with compositions simulating the pore liquid of hardened concretes. The concrete prism expansion test at 38 °C and RH > 95% (traditional CPT) was taken as a reference test, in order to define the appropriate expansion limit criterion for the proposed accelerated CPT. Three natural aggregates of known field performance and different alkali–silica reactivity were tested. The compositions of alkaline solutions were designed by assuming total dissolution of cement alkalis and taking a ratio between the mass fractions of effective water consumed by cement hydration and of alkalis uptaken by cement hydrates equal to unity. This simplified approach was found in an acceptable agreement with literature empirical equations correlating pore solution alkalinity of hardened Portland cement mixes with total alkali content of cement. Elaboration of expansion data through both pass-fail and threshold alkali level (TAL)-evaluation approaches indicated that, for the accelerated CPT, an expansion limit criterion of 0.04% after 120 days of testing in alkaline solutions is appropriate to evaluate the aggregate alkali reactivity congruently with the traditional CPT. Use of the proposed test method in place of the traditional CPT would reduce the test duration from 365 to 120 days.

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Section: Factors Affecting Pore Liquid Alkalinitymentioning

confidence: 99%

Section: Factors Affecting Pore Liquid Alkalinitymentioning

confidence: 99%

Assessment of Alkali–Silica Reactivity of Aggregates by Concrete Expansion Tests in Alkaline Solutions at 38 °C

et al. 2020

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“…The pore solution of wPc is slightly different from other Portland cements since it has a lower alkali content (i.e. K and Na), producing a decrease in the available content of SO4 2and OHions available to react with C3A during hydration, lowering the production of ettringite (Richardson et al, 2016;Sanjuán et al, 2019).…”

Section: White Portland Cement and Grey Portland Cement (Wpc And Gpc)mentioning

confidence: 97%

Early-age characterisation of Portland cement by impedance spectroscopy

Gallardo

Provis

2022

Advances in Cement Research

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This paper applies alternating current impedance spectroscopy to assess the effect of different sand, anhydrite, and water contents on the electrochemical response of Portland cement in the early stages of hydration. Potential factors that may affect impedance measurements and data interpretation are also discussed, such as the complexity of cement chemical composition, its physical properties and hydration kinetics, and technique limitations. The impedance data obtained are benchmarked against different supporting techniques and literature data, showing a strong relationship among hydration rates as determined by thermochemistry, setting time measurements by physical approaches, pore fluid chemistry, electrical conductivity, and the impedance behaviour observed. The results demonstrate that ACIS is a sensitive technique to assess cement hydration, enabling differentiation of changes in the water and cement content, hydration degree, and microstructural development during the first 24 hours after mixing.

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“…Furthermore, it has been demonstrated the effect of aluminum on reducing quartz dissolution in the high alkalinities found in cement paste. Nevertheless, the reduction in the dissolution rate of amorphous silica due to the presence of aluminum decreases as the pH increased [62] and the positive effect on the ASR is almost the same irrespective of the aluminum concentration in the pore solution [53] because the aluminum incorporation level is independent of such concentration.…”

Section: Alkali-aggregate Mitigation By Pozzolanic Additions In Cemen...mentioning

confidence: 99%

Sustainable and Durable Performance of Pozzolanic Additions to Prevent Alkali-Silica Reaction (ASR) Promoted by Aggregates with Different Reaction Rates

et al. 2020

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The increased use of industrial wastes and by-products to produce concretes and blended cements is a lever to achieve carbon neutrality. Furthermore, they could improve their durability. Some pozzolanic additions can minimize the alkali-silica reaction (ASR), which is a well-known deleterious process that occurs between some reactive aggregates and the alkaline pore solution found in mortars and concretes. This work quantifies the efficiency of four pozzolanic materials (natural pozzolan, P, siliceous coal fly ash, V, silica fume, D, and blast-furnace slag, S) assessed by means of compressive strength testing, open porosity, ASR-expansion measurements, and SEM microscopy. Accelerated expansion tests were performed in mortar bars with a cement/sand ratio of 1/2.25 and a water/cement ratio of 0.47, two reactive aggregates and a non-reactive one. The major contributions of this paper are: (i) The more aggregate reactivity is, the higher ASR mitigation level was found when additions were added and (ii) The best additions for ASR inhibition are silica fume and fly ash.

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Alkali Ion Concentration Estimations in Cement Paste Pore Solutions

Cited by 7 publications

References 25 publications

Assessment of Alkali–Silica Reactivity of Aggregates by Concrete Expansion Tests in Alkaline Solutions at 38 °C

Assessment of Alkali–Silica Reactivity of Aggregates by Concrete Expansion Tests in Alkaline Solutions at 38 °C

Early-age characterisation of Portland cement by impedance spectroscopy

Sustainable and Durable Performance of Pozzolanic Additions to Prevent Alkali-Silica Reaction (ASR) Promoted by Aggregates with Different Reaction Rates

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