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  • How does fly ash mitigate alkali–silica reaction

    01.03.2013· Even when the Na 2 O eq content of fly ash is higher than cement's, the dilution effect is observed as only a portion of fly ash alkalis are soluble per ASTM C311 test, ; and even that portion dissolves slowly in the pore solution due to slower reactivity of fly ash in comparison with Portland cement . (2) Alkali binding: the additional pozzolanic C–S–H is able to bind alkali and

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  • Alkali-Aggregate Reaction in Concrete

    This amount appears to depend on the alkali content of the fly ash and on the chemical composition of the fly ash used, mainly calcium oxide content. For some high calcium fly ashes with more than 1.5 percent available alkali content, a "pessimum limit" was observed. Such a limit represents a percent replacement under which the addition of fly ash causes equal or greater expansions in the

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  • Characteristics and Performance of Fly Ash from Sodium

    These reports indicate that the i ssue is likely a combination of the alkali content of the coal and resulting baseli ne fly ash and the added sorbent. It has also been indicated that some facilities may have a variable injection schedule, resulting in variable sodium content in the final fly ash product. The added sodium from the sodium sorbent will increase the sodium content of the fly ash

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  • Mechanical property and structure of alkali

    17.12.2012· Mechanical property and structure of alkali-activated fly ash (FA)/ground granulated blast furnace slag (GGBFS) blends were investigated via compressive strength testing, X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy/energy dispersive spectroscopy. It is shown that the incorporation of slag into solid precursors can improve

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  • Available alkalis in fly ash and their effects on alkali

    Relationship between water soluble alkalis and sulfate content in fly ash 81 FIGURE 18. Alkali dissolution rates vs. N/S mole ratio 84 FIGURE 19. Alkali dissolution rates vs. C/S mole ratio 85 FIGURE 20. Alkali dissolution rates vs. C/(S+A+F) mole ratio 85 FIGURE 21. Relation between silica content and curing time for equal relative available alkalis release at curing temperature of 38°C and

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  • Available alkalis in fly ash and their effects on

    Replacements of low-alkali cement with Class C fly ash up to 40% also increased expansion. A critical N/S mole ratio was identified and found to characterize alkali reactivity. The replacement of the cement with fly ash was found to provide a degree of protection from external alkali attack. Expansions caused by external alkali attack were found to be inversely related to the N/S mole ratio of

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  • DETERMINATION OF REACTIVE SILICA IN FLY

    Reactive silica in fly ash is that fraction of the total silica which is soluble in both acids and alkalis. The IS method [IS 3812 (Part-1) 2013 Annexure-B] of determining reactive silica is incomplete as it proposes treatment with HCl alone. So we would like to propose a method in which reactive silica is determined gravimetrically by subtracting the silica content of the residue obtained by

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  • Dissolution of the glassy phase in low-calcium fly

    20.06.2018· The X-ray diffraction pattern of the fly ash glassy phase is adequately fit using a single pseudo-Voigt (PV) peak. The peak position of the PV fit is invariant of the dissolution of the glassy phase and an intensity-based measure of the X-ray diffraction analysis intensity pattern with the PV fit provides an accurate estimate of the undissolved glassy content present in the fly ash.

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  • INFLUENCE OF ALKALI CONTENT OF FLY ASH

    Eight mixtures containing various ratios of high- or low-alkali fly ash and cement, and two control mixtures were made to determine the influence of the alkali content of fly ash on its effectiveness in preventing expansion of mortar bars made from the mixtures. Mortar bars were cast and their lengths measured at 2, 14, and 28 days, 6 months, and 1 year.

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  • fly ash alkali content requirements costarica

    How does fly ash mitigate alkali–silica reaction ASR in. Although the K 2 O content of F1 fly ash is higher than the PC 116 versus 089 the 15F1 mortar shows 43 less K at 0 day due to a slower reaction and release of alkalis by fly ash During the first 24 h K increases in all three mortars due to dissolution from cement and fly ash. More Details >

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  • POZZOLANIC REACTION OF FLY ASH CEMENT PASTE IN THE

    diameter pore volume of fly ash cement paste. The alkali-injected starting time 1 month after casting was more effective in reducing 20-330 nm ranged diameter pore volume than 3 months after casting. Keywords: pozzolanic reaction, alkali activator, Ca(OH) 2 content, pore volume 1. INTRODUCTION Fly ash has been used widely in replacing a partial of cement which is one of the main materials used

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  • Available alkalis in fly ash and their effects on

    Replacements of low-alkali cement with Class C fly ash up to 40% also increased expansion. A critical N/S mole ratio was identified and found to characterize alkali reactivity. The replacement of the cement with fly ash was found to provide a degree of protection from external alkali attack. Expansions caused by external alkali attack were found to be inversely related to the N/S mole ratio of

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  • The Role of Fly Ash Composition Reducing Alkali-Silica

    For example, ACI 318 limits the fly ash content of concrete exposed to deicing salts to 25% of cementitious materials in order to prevent problems with deicer scaling. While 25% is an adequate dosage for most Class F fly ashes to control ASR, it is often not sufficient for Class C ashes. Other practical considerations might include early-age strength requirements for form removal or the

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  • Alkali Content of Fly Ash – Measuring and

    KEYWORDS. Alkali content, Alkali silica reactions, Cracking, Fly ash, Iowa, Potassium, Quality control, Sodium, Specifications

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  • Observations on the Rheological Response of Alkali

    1 Observations on the Rheological Response of Alkali Activated Fly ash 2 Suspensions: O in the activator to the total fly ash content; and (ii) M s – the ratio of . Page 5 84 SiO 2-to-Na 2 O in the activator. Two different n values were used: 0.03 and 0.05. The mass-based M s values 85 of the as-obtained Na- and K-silicates were 3.22 and 2.10 respectively, which corresponds to mole-based

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  • Fly Ash Classification Old and New Ideas

    a useful alkali index of fly ash chemistry that correlates with the Nr values at least as well as the ASI and modified ASI values, and may be preferred to them. Average cv values for fly ashes of all ranks and coal basins worldwide are given in Tables 1 and 2. Typical cv values for fly ashes from bituminous and anthracite coals are low or negative numbers, unless there is elevated iron content

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  • Alkali Content of Fly Ash – Measuring and

    KEYWORDS. Alkali content, Alkali silica reactions, Cracking, Fly ash, Iowa, Potassium, Quality control, Sodium, Specifications

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  • Alkali Content of Fly Ash – Measuring and

    KEYWORDS. Alkali content, Alkali silica reactions, Cracking, Fly ash, Iowa, Potassium, Quality control, Sodium, Specifications

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  • Fly ash geopolymer concrete: Significantly

    Fly ash-based geopolymer binders consist of two components: The fly ash and an alkali activator. Usually, fly ash is used as produced in the power station, with no need for further treatment.

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  • Alkali Content of Fly Ash – Measuring and

    The lab study focused on the available alkali test and how fly ash alkali content impacts common performance tests (mortar-bar expansion tests). Twenty-one fly ash samples were evaluated during the testing. The field study focused on the inspection and testing of selected, well documented pavement sites that contained moderately reactive fine aggregate and high-alkali fly ash. A total of nine

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What is the alkali content in fly ash

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