Interactions of carbon-containing fly ash with commercial air-entraining admixtures for concrete

Freeman, Elizabeth; Gao, Yuan; Hurt, Robert H.; Suuberg, Eric M.

doi:10.1016/s0016-2361(96)00193-7

Cited by 125 publications

(82 citation statements)

References 3 publications

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“…An increment in the loss on ignition (LOI) of the fly ash increases the water requirement for a given consistency [26]. The same carbon cellular particles which affect the water content also affect the air content, making it necessary to increase the air entraining admixture significantly to achieve the desired air content [27]. Although these non compliant fly ashes could have an effect on concrete water or admixture demand, it is evident they have a positive effect as a cementitious material and can be used in different concrete applications [28,29]; for instance, they have been evaluated to be used in pervious concretes [29].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of activated high volume fly ash systems using Na 2 SO 4 , lime and quicklime in mortars with high loss on ignition fly ashes

Velandia

Lynsdale

Provis

et al. 2016

Construction and Building Materials

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Article available under the terms of the CC-BY-NC-ND licence (https://creativecommons.org/licenses/by-nc-nd/4.0/) eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. The effect of sodium sulfate, added as an activator, is significant in terms of compressive strength at early age for two of the fly ashes studied; in this case, the parameter used to correlate with the compressive strength evolution is the amount of portlandite consumed through pozzolanic reactions. However, sodium sulfate does not have the same effect on fly ashes with a high amount of Fe 2 O 3 , in which portlandite consumption is much lower.

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Section: Introductionmentioning

confidence: 99%

Evaluation of activated high volume fly ash systems using Na 2 SO 4 , lime and quicklime in mortars with high loss on ignition fly ashes

Velandia

Lynsdale

Provis

et al. 2016

Construction and Building Materials

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“…The surfactant adsorption capacity of the treated and untreated carbon black samples was determined by titration procedure referred to as the foam index test [18,21]. Foam index measurements involved placing the test carbon sample [usually about 90 mg] together with 8 grams of Portland cement and 25 ml of de-ionized water into a 70 ml cylindrical jar with a 40 mm I.D., 80 mm length.…”

Section: Methodsmentioning

confidence: 99%

“…Oxidation imparts hydrophilicity to carbon surfaces [16,17], which is desirable for Hg-sorbents used in power station applications, where contamination of fly ash by hydrophobic activated carbon adversely affects the properties of fly ash concrete [16,18]. In previous experiments from our laboratory, ozone treatment did increase the hydrophilicity of activated carbon as desired, but did not enhance the performance of the activated carbon as mercury sorbent, and under some conditions degraded the performance.…”

Section: Introductionmentioning

confidence: 91%

High capacity mercury adsorption on freshly ozone-treated carbon surfaces

Manchester

Wang

Külaots

et al. 2008

Carbon

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A set of carbon materials was treated by a choice of common oxidizers to investigate the mercury capture capacities at varying temperature conditions. It was found that ozone treatment dramatically increases the mercury capture capacity of carbon surfaces by factors up to 134, but the activity is easily destroyed by exposure to the atmosphere, to water vapor, or by mild heating. Freshly ozonetreated carbon surfaces are shown to oxidize iodide to iodine in solution and this ability fades with aging. FTIR analysis shows broad C-O stretch features from 950 to 1300 cm −1 , which decay upon atmospheric exposure and are similar to the C-O-C asymmetric stretch features of ethylene secondary ozonide. The combined results suggest that the ultra-high mercury capture efficiency is due to a subset of labile C-O functional groups with residual oxidizing power that are likely epoxides or (epoxide-containing) secondary ozonides. The results open the possibility for in situ ozonolysis to create high-performance carbon-based Hg sorbents.

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“…In recent studies, surfactant adsorption on carbon has been identified as a key phenomenon determining the suitability of coal combustion fly ash as a concrete additive [5][6][7][8][9]. Here the carbon is a contaminant and its undesirable adsorption of surfactant from the aqueous concrete paste reduces the surfactant's ability to stabilize sub-millimeter air bubbles that help improve freeze-thaw resistance in set concrete [10].…”

Section: Introductionmentioning

confidence: 99%

“…Here the carbon is a contaminant and its undesirable adsorption of surfactant from the aqueous concrete paste reduces the surfactant's ability to stabilize sub-millimeter air bubbles that help improve freeze-thaw resistance in set concrete [10]. Previous studies [5,7,11,12] have related the extent of adsorption to four factors: (1) the amount of residual carbon in ash, (2) the total carbon surface area, (3) the accessibility of the surface as governed by pore and particle size distribution, and (4) the state of carbon surface oxidation. Oxidation of carbon surfaces by either air or ozone has been shown to reduce the extent of concrete surfactant adsorption [7].…”

Section: Introductionmentioning

confidence: 99%

Strategies and Technology for Managing High-Carbon Ash

Hurt¹,

Suuberg²,

Veranth³

et al. 2002

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The overall objective of the present project is to identify and assess strategies and solutions for the management of industry problems related to carbon in ash. Specific research issues to be addressed include:• the effect of parent fuel selection on ash properties and adsorptivity, including a first ever examination of the air entrainment behavior of ashes from alternative (non-coal) fuels.• the effect of various low-NOx firing modes on ash properties and adsorptivity• the kinetics and mechanism of ash ozonation. This data will provide scientific and engineering support of the ongoing process development activities.During this fourth project period we completed the characterization of ozone-treated carbon surfaces and wrote a comprehensive report on the mechanism through which ozone suppresses the adsorption of concrete surfactants.4

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Interactions of carbon-containing fly ash with commercial air-entraining admixtures for concrete

Cited by 125 publications

References 3 publications

Evaluation of activated high volume fly ash systems using Na 2 SO 4 , lime and quicklime in mortars with high loss on ignition fly ashes

Evaluation of activated high volume fly ash systems using Na 2 SO 4 , lime and quicklime in mortars with high loss on ignition fly ashes

High capacity mercury adsorption on freshly ozone-treated carbon surfaces

Strategies and Technology for Managing High-Carbon Ash

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