Reactivity and self-hardening of fly ash from the fluidized bed combustion of wood and peat

Illikainen, Mirja; Tanskanen, Pekka; Kinnunen, Päivö; Körkkö, Mika; Peltosaari, Olli; Wigren, Valter; Österbacka, Jan; Talling, Bob; Niinimäki, Jouko

doi:10.1016/j.fuel.2014.06.029

Cited by 56 publications

(38 citation statements)

References 23 publications

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“…When comparing these results to earlier published work [9,16,29,35], it can be seen that the achieved activity indexes are lower for classified fly ashes (Fig. 7) than for original fly ashes.…”

Section: Mortar Experimentssupporting

confidence: 62%

“…7) than for original fly ashes. The reason for this is probably the lower reactivity of classified ashes: calcium and sulfur are important components for FBC fly ash reactivity [16,35], and in this present work, many of those components were removed from the fraction used to replace cement. Because of this, aiming to fulfill concrete standards is questionable for FBC fly ash if significant strength loss is not wanted.…”

Section: Mortar Experimentsmentioning

confidence: 82%

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Mechanically Treated Fly Ash from Fluidized Bed Combustion of Peat, Wood, and Wastes in Concrete

Ohenoja

Wigren²,

Österbacka

et al. 2019

Waste Biomass Valor

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Fly ash generation in fluidized bed combustion (FBC) is a critical issue in many countries due to its disposal is becoming increasingly restricted and expensive. Because of this, there is a demand for applications in which these types of fly ashes could be utilized efficiently. One promising use for FBC fly ashes is as a cement replacement material in mortar and concrete. The current concrete regulations do not allow the use FBC fly ash as a supplementary cementitious material, but it can be expected to be included in the standards in the future. The properties of FBC fly ashes typically do not fulfill the values set in the standards as such. This study aimed to establish whether the properties of fly ashes from FBC of peat, wood, and wastes can be modified by mechanical classification and grinding so that they meet the requirements of the standards. The sulfate and chloride content, the sum of the main components (Si, Al, Fe), and the fineness of material were analyzed before and after the classification and grinding processes. In addition, the mortar specimens were prepared by using the processed fly ash as a cement replacement material. It was found that air jet classification is an effective fractionating method for fly ashes that effectively removes sulfate and chloride into fine fraction. Classified and ground fly ashes are potential alternative cement replacement materials. It is possible to achieve 80% of the control sample's compressive strength and 90% of the control sample's flexural strength for mortars containing 20% of classified and ground FBC fly ashes. Graphical AbstractLow utilization potential fly ash Fine fraction: 10 -30% fly ash~ Hazardous components: heavy metals, SO 4 , Cl Coarse fraction: 70 -90% fly ash C hemical composition fulfills EN 450-1 concrete standard Waste disposal stabilization Grinding High value product, e.g. for concrete air air Air jet classificationThis study aimed to establish whether the utilization potential of fly ashes from FBC of peat, wood, and wastes can be improved in concrete by mechanical classification and grinding, which is not done earlier. We found that it is possible to modify these fly ashes to fulfill concrete standards. Usually it is thought that fly ashes from fluidized bed combustion are not suitable for standardized concrete, but this study shows that with treatments it is possible.

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Section: Mortar Experimentssupporting

confidence: 62%

Section: Mortar Experimentsmentioning

confidence: 82%

Mechanically Treated Fly Ash from Fluidized Bed Combustion of Peat, Wood, and Wastes in Concrete

Ohenoja

Wigren²,

Österbacka

et al. 2019

Waste Biomass Valor

Self Cite

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“…4b), can be associated with the formation of ettringite (Han et al 2014;Taylor 1997) and syngenite (Han et al 2014). The ettringite has been found to be one of the main hydration products in selfhardening of these type of ashes (Illikainen et al 2014). With MFA, the first peak clearly increased with the increasing replacement level.…”

Section: Heat Of Hydrationmentioning

confidence: 99%

Partial Replacement of Portland-Composite Cement by Fluidized Bed Combustion Fly Ash

Rissanen

Ohenoja

Kinnunen

et al. 2017

J. Mater. Civ. Eng.

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Fly ash from fluidized bed combustion differs greatly from that of pulverized coal firing. The most noticeable differences are in morphology, reactivity, and chemical composition. The utilization of biomass fly ash from fluidized bed combustion as a cement replacement material could be a promising method for both minimizing the amount of landfilled fly ash and reducing CO2 emissions in the concrete and cement industry. In this study, fly ash from fluidized bed combustion of peat and forest industry residue was used as a supplementary cementitious Manuscript Click here to download Manuscript Manuscript_Revised.docx material for CEM II composite cement which contains OPC, blast furnace slag, and limestone. Even with a 40% cement replacement ratio the compressive strengths of the mortar samples were still as high as 88% of the control sample's strength. Comparison with un-reactive replacement material revealed that moderate hydraulic properties of the studied fly ash explained the positive effects on strength rather than filler or nucleation effects.

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“…Hydration of amorphous silicate phases may also contribute [6] and C-S-H gel was identified by SEM-EDX [8]. The importance of each reaction and the relation between WA properties and its self-hardening behavior is though yet not known [9], though a deeper knowledge is necessary in order to understand and evaluate the quality of WA for use in concrete.…”

Section: Characterization Of the Ashesmentioning

confidence: 99%

Wood ash used as partly sand and/or cement replacement in mortar

Ottosen¹,

Hansen

Jensen³

et al. 2016

Int. J. SDP

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Wood ash (WA) is the residue generated during incineration of wood and wood products. The WAs in focus of this work are from incineration of virgin wood. Physical and chemical properties of WA vary significantly depending on many factors related to the wood species and the incineration process, and the present work reports a characterization of three different WAs. Properties of mortar samples with the WAs used as partly cement and/or sand replacement are reported. Compressive strength development and porosity are the mortar properties in focus. The overall aim of the work is to evaluate the influence from the differences in ash characteristics to the properties of the mortar samples. The characteristics of the ashes did vary considerably. For example, one ash had very high loss on ignition (LoI) of 14% compared to 3% for the other ashes. Ash solubility in water ranged from 18% to 28%. Two of the ashes were dry and sampled just after the incineration, whereas one ash had a water content of 15%, because the ash was sprayed with water to avoid dust during ash handling at the incineration plant. Regardless of replacing cement or sand with WAs, the compressive strength decreased compared to a reference without ash, however, the decrease was small for two of the ashes. Using the ash with the high LoI resulted in significantly lower compressive strength compared to the other two ashes. The mortar samples with two of the ashes (with low LoI) had qualities, which were very encouraging in order to use WA as partly cement replacement (<10%). At higher percentages the workability was so low that extra water needed to be added and the results depended on the water:cement ratio rather than the ash mass.

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Reactivity and self-hardening of fly ash from the fluidized bed combustion of wood and peat

Cited by 56 publications

References 23 publications

Mechanically Treated Fly Ash from Fluidized Bed Combustion of Peat, Wood, and Wastes in Concrete

Mechanically Treated Fly Ash from Fluidized Bed Combustion of Peat, Wood, and Wastes in Concrete

Partial Replacement of Portland-Composite Cement by Fluidized Bed Combustion Fly Ash

Wood ash used as partly sand and/or cement replacement in mortar

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