Effects of Soak Solution Type on Alkali Release from Volcanic Aggre-gates − Is Alkali Release Really Responsible for Accelerating ASR Expansion? −

Kawabata, Yuichiro; Yamada, Kazuo; Igarashi, Go; Sagawa, Yasutaka

doi:10.3151/jact.16.61

Cited by 12 publications

(9 citation statements)

References 17 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%

“…Thermodynamic modelling [36], as well as semi-empirical models [34] based on the interaction between C-S-H gel and pore liquid have been proposed for calculating the alkali uptake by C-S-H gel. The amount of water combined during Portland cement hydration may be evaluated using well-known relationships concerning capillary and total porosity of Portland cement pastes [25].…”

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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“…Also, the alkalis released from the aggregates could increase the hydroxyl ion concentrations in the concrete [15,16]. In particular, the content of the alkali released is enhanced by the high alkalinity of the solution [15]. Also, for the concrete affected by ASR, alkalis are released with the accompanying dissolution of silicate anions [15].…”

Section: Cementmentioning

confidence: 99%

“…In particular, the content of the alkali released is enhanced by the high alkalinity of the solution [15]. Also, for the concrete affected by ASR, alkalis are released with the accompanying dissolution of silicate anions [15]. Both are balanced with alkali metal ions.…”

Section: Cementmentioning

confidence: 99%

Alkali Ion Concentration Estimations in Cement Paste Pore Solutions

Sanjuán¹,

Estévez

Argiz

2019

Applied Sciences

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The alkalinity of the pore solution is of great interest for evaluating the rising of the alkali–silica reaction (ASR) when reactive amorphous silica is found in some aggregates in some cement-based composites. This reaction is not desirable because it generates swelling gel materials around the aggregates, which produce an expansive pressure inside concrete over time, and can cause the cracking of concrete, leading to serious structural problems. The purpose of this study is to develop a quick, easy and reliable method to estimate the available alkali concentrations in the pore solution of cement-based composites. The bound alkalis were initially calculated based on Taylor’s alkali distribution method. The proposed procedure to estimate the available alkalis content is a reliable method for use in construction and building composite materials.

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“…However, in real concrete, some minerals, such as clay, Ramlochan may bind with a certain amount of alkali, which results in a lower hydroxide ion concentration , and alkalis can be released from alkalibearing minerals over long time frames (Bérubé et al 2002;Bérubé et al 2008;Sims et al 2012). The latter issue remains controversial whether alkali release really increases hydroxide ion concentration (Kawabata et al 2018). The former issue would especially influence the hydroxide ion concentration in the early stage of testing, which is critical for proportional pessimum effect (Kawabata and Yamada 2017).…”

Section: Alkali Concentration Of Wrapping Clothmentioning

confidence: 99%

Alkali-Wrapped Concrete Prism Test (AW-CPT) – New Testing Protocol Toward a Performance Test against Alkali-Silica Reaction–

Kawabata

Yamada

Sagawa

et al. 2018

ACT

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A new testing protocol, Alkali-Wrapped Concrete Prism Test (AW-CPT), is proposed to avoid alkali leaching and drying, which considerably influence expansion behavior of concrete affected by alkali-silica reaction (ASR). The approach used in this test is that a concrete specimen is wrapped by wet cloth containing alkali solution mimicking the alkalinity of the concrete pore solution. The proposed testing protocol was validated through laboratory and field-exposure measurements, with a focus on expansion, alkali mass balance, and mass change. The test results clearly showed that alkali leaching and drying were significantly reduced by using the AW-CPT method. AW-CPT gives a conservative threshold total alkali content, while conventional CPT overestimates it. The test results also highlighted that there may be an optimum condition of temperature and level of alkali boosting for each reactive aggregate.

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Effects of Soak Solution Type on Alkali Release from Volcanic Aggre-gates − Is Alkali Release Really Responsible for Accelerating ASR Expansion? −

Cited by 12 publications

References 17 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

Alkali Ion Concentration Estimations in Cement Paste Pore Solutions

Alkali-Wrapped Concrete Prism Test (AW-CPT) – New Testing Protocol Toward a Performance Test against Alkali-Silica Reaction–

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