Hydration of coal–biomass fly ash cement

Tkaczewska, Ewelina; Małolepszy, Jan

doi:10.1016/j.conbuildmat.2008.12.018

Cited by 49 publications

(42 citation statements)

References 12 publications

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“…The chemical composition of biomass fly ash is an important characteristic to consider when using it as a supplementary cementing material in blended cement. Tkaczewska [20] found that, during hydration, the cement samples that contain coal and biomass fly ash show lower heat flow values, a higher quantity of Ca(OH) 2 , and slower C 3 S hydration in comparison with samples containing bituminous coal fly ash as an additive. Researchers have noted that a wood ash concrete requires a higher quantity of water [21].…”

Section: Introductionmentioning

confidence: 99%

Influence of different artificial additives on Portland cement hydration and hardening

Kaminskas

Cesnauskas

Kubiliute

2015

Construction and Building Materials

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Section: Introductionmentioning

confidence: 99%

Influence of different artificial additives on Portland cement hydration and hardening

Kaminskas

Cesnauskas

Kubiliute

2015

Construction and Building Materials

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“…Wide use of fly ashes in cement and concrete is determined by their pozzolanic activity, defined as ability to react with calcium hydroxide, a by-product of Portland cement hydration process, to form additional calcium silicate hydrates (C-S-H) and other cementitious compounds, that is, calcium aluminate hydrates (C 2 AH 8 and C 4 AH 13 ) and calcium aluminosilicate hydrates (C 2 ASH 8 and C 3 AS 3 -C 3 AH) [1]. Scientific literature shows that rate of pozzolanic reaction is attributed to many factors such as particle size distribution, specific surface area, chemical and mineral composition of the fly ashes [2][3][4][5][6][7], which should be taken into account for predicting contribution of these materials in cement. Work [8] shows that fineness of ashes is more important factor and gives much effect on pozzolanic properties of them.…”

Section: Introductionmentioning

confidence: 99%

“…Cement containing fly ashes has lower hydraulic activity in comparison to that of Portland cement, that is, hydra-tion process of fly ash cement is a relatively slower. Lower heat evolution rate of fly ash-Portland clinker mixture is confirmed by longer induction period and lower intensity of main peak on microcalorimetric curve [1,[3][4][5][6][18][19][20][21][22]. Fly ashes delay initial and final setting times of cement pastes [1,23,24] and decrease early strength of cement mortars, mainly due to dilution effect as well as slower rate of pozzolanic reaction at initial stage, to about 28 days.…”

Section: Introductionmentioning

confidence: 99%

Mechanical Properties of Cement Mortar Containing Fine-Grained Fraction of Fly Ashes

Tkaczewska¹

2013

OJCE

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This paper presents the effect of fly ash grain-size fractions on Portland-fly ash cement hydration and its properties. Siliceous fly ashes of size fraction of 0 -16 and 16 -32 µm, separated from initial fly ash samples from 1 st , 2 nd and 3 rd hopper in ESP system, were analysed. Cement hydration was investigated by determination of hydration heat and content of Ca(OH) 2 and C 3 S in cement samples. Water to cement ratio and initial setting time of cement pastes as well as compressive strength and microstructure of cement mortars were also analyzed. Results showed that the same amount of the same size ash fraction can give cement of lower or higher early strength and its lower or higher increase with time. Incorporation of 20 wt% of ash fraction of 0 -16 µm can produce Portland-fly ash cement CEM II/A-V of strength class 42.5R (from 2 nd hopper) or 52.5N (from 3 rd hopper). Cement containing 40 wt% of ash fraction of 0 -16 µm from 2 nd and 3 rd hopper can be classified as pozzolanic cements CEM IV/A-V of strength class 42.5 and normal or rapid early strength, respectively. Different development of strength of cement with addition of the same size ash fraction separated from the initial ash sample from the next hopper in ESP system is connected with higher depolymerization degree of SiO 4 units in ash glass, resulting from the greater amount of AlO 4 units replacing SiO 4 units. Ash fraction of 16 -32 µm shows lower depolymerisation of glass network and as a consequence lower hydration degree of C 3 S to portlandite and calcium silicate hydrates (C-S-H).ashes reveal greater amount of glassy component than their coarse fractions, which result from higher amount of grains below 45 μm, especially below 10 µm [1][2][3][4]. Ash fraction of 0 -45 μm is characterized by the greatest amount of active components, that is, SiO 2 and Al 2 O 3 , whoes total content is approximately 15% -20% according to ASTM C379-65T. The coarse ash fraction lowers content of active silica and aluminum oxide in it, which generally does not exceed 10% in case of fraction above 100 μm. Works [4,[8][9][10] presented that fly ashes separated from different hoppers, attached to an electrostatic precipitator system after coal combustion, have variable physical and chemical properties. Ashes collected from 3 rd hopper have improved fineness and particle size distribution in form of a normal distribution curve. Also, they show lower amount of SiO 2 , but greater amount of Al 2 O 3 and alkalies (Na 2 O and K 2 O) [2,6,7]. Consequence of that is increase in content of active chemical components in ash from 3 rd hopper, especially the largest increase is observed for active Al 2 O 3 [4]. According to E. TKACZEWSKA 55 Tkaczewska [2], summarized amount of active chemical components in ash of 0 -16 µm is higher than that in traditional siliceous fly ashes and difference could be as much as 1.5 times. Of course, this is due to greater fineness fly ash of 0 -16 µm, but also can be resulted from different chemical composition and structure of glassy compone...

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“…The ASTM (American Standard Testing and Materials) C618 prohibits the use of biomass fly ash in concrete, but the European Commission has approved a standard to allow the use of biomass fly ash (up to 25 wt.% straw co-firing with coal) in concrete. Meanwhile, investigations in laboratories are rare and therefore this does not give a unified conclusion on the utilization of fly ash from biomass co-firing in the concrete industry [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation on biomass co-firing in a 300 MW pulverized coal-fired utility furnace in China

Wang

Tan

Niu

et al. 2011

Proceedings of the Combustion Institute

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Hydration of coal–biomass fly ash cement

Cited by 49 publications

References 12 publications

Influence of different artificial additives on Portland cement hydration and hardening

Influence of different artificial additives on Portland cement hydration and hardening

Mechanical Properties of Cement Mortar Containing Fine-Grained Fraction of Fly Ashes

Experimental investigation on biomass co-firing in a 300 MW pulverized coal-fired utility furnace in China

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