Dry-processing of long-term wet-stored fly ash for use as an addition in concrete

M. J. McCarthy (Lead / Corresponding author), L. Zheng, R. K. Dhir, G. Tella

Research output: Contribution to journalArticle

7 Citations (Scopus)
152 Downloads (Pure)

Abstract

The paper describes a study carried out to explore the potential for recovery of fly ash from wet-storage areas for use as an addition in concrete, and involved drying and processing material to achieve finer fractions/reduce particle size. Three relatively coarse fly ashes with medium/high carbon contents (loss-on-ignition; LOI) were obtained from two UK lagoons and a stockpile. Initially, drying (105 °C) and screening (600 μm) were carried out, giving acceptable handling properties. Thereafter, processing using (63 μm) sieving, air classifying or grinding was investigated. The methods gave increased fineness levels (greatest with grinding), with some reductions in LOI also found after sieving and air classifying. Assessment of fly ash reactivity indicated improvements with processing, and most noticeable effects by grinding. Tests on concrete found that both consistence (slump) and compressive (cube) strength increased with processing and tended to follow fly ash fineness. Further analysis showed that strength could be related to the sub 10 μm particle level in fly ash. This appeared to be irrespective of processing method, with progressive increases (in strength) up to sub 10 μm contents of about 60% (maximum in the study). Concrete tests for water absorption and intrinsic (air) permeability, carbonation and chloride diffusion showed that these were also influenced by fly ash sub 10 μm content. The factors affecting behaviour are discussed and practical implications of the research considered.

Original languageEnglish
Pages (from-to)205-215
Number of pages11
JournalCement and Concrete Composites
Volume92
Early online date16 Oct 2017
DOIs
Publication statusPublished - Sep 2018

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Coal Ash
Fly ash
Concretes
Processing
Drying
Carbonation
Water absorption
Compressive strength
Ignition
Chlorides
Screening
Carbon
Particle size
Recovery

Keywords

  • Drying and screening
  • Reactivity
  • Sieving, air classifying and grinding
  • Use in concrete
  • Wet-stored fly ash

Cite this

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title = "Dry-processing of long-term wet-stored fly ash for use as an addition in concrete",
abstract = "The paper describes a study carried out to explore the potential for recovery of fly ash from wet-storage areas for use as an addition in concrete, and involved drying and processing material to achieve finer fractions/reduce particle size. Three relatively coarse fly ashes with medium/high carbon contents (loss-on-ignition; LOI) were obtained from two UK lagoons and a stockpile. Initially, drying (105 °C) and screening (600 μm) were carried out, giving acceptable handling properties. Thereafter, processing using (63 μm) sieving, air classifying or grinding was investigated. The methods gave increased fineness levels (greatest with grinding), with some reductions in LOI also found after sieving and air classifying. Assessment of fly ash reactivity indicated improvements with processing, and most noticeable effects by grinding. Tests on concrete found that both consistence (slump) and compressive (cube) strength increased with processing and tended to follow fly ash fineness. Further analysis showed that strength could be related to the sub 10 μm particle level in fly ash. This appeared to be irrespective of processing method, with progressive increases (in strength) up to sub 10 μm contents of about 60{\%} (maximum in the study). Concrete tests for water absorption and intrinsic (air) permeability, carbonation and chloride diffusion showed that these were also influenced by fly ash sub 10 μm content. The factors affecting behaviour are discussed and practical implications of the research considered.",
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author = "McCarthy, {M. J.} and L. Zheng and Dhir, {R. K.} and G. Tella",
note = "The Authors would like to acknowledge the RMC Environment Fund, Innogy PLC, John Doyle Ltd, Castle Cement Ltd and Aggregate Industries UK Ltd for funding the work described. These organisations and the UK Quality Ash Association are thanked for their technical input. The contribution of Bradley Pulverizer Ltd in carrying out the air classification is much appreciated.",
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Dry-processing of long-term wet-stored fly ash for use as an addition in concrete. / McCarthy, M. J. (Lead / Corresponding author); Zheng, L.; Dhir, R. K.; Tella, G.

In: Cement and Concrete Composites, Vol. 92, 09.2018, p. 205-215.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Dry-processing of long-term wet-stored fly ash for use as an addition in concrete

AU - McCarthy, M. J.

AU - Zheng, L.

AU - Dhir, R. K.

AU - Tella, G.

N1 - The Authors would like to acknowledge the RMC Environment Fund, Innogy PLC, John Doyle Ltd, Castle Cement Ltd and Aggregate Industries UK Ltd for funding the work described. These organisations and the UK Quality Ash Association are thanked for their technical input. The contribution of Bradley Pulverizer Ltd in carrying out the air classification is much appreciated.

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Y1 - 2018/9

N2 - The paper describes a study carried out to explore the potential for recovery of fly ash from wet-storage areas for use as an addition in concrete, and involved drying and processing material to achieve finer fractions/reduce particle size. Three relatively coarse fly ashes with medium/high carbon contents (loss-on-ignition; LOI) were obtained from two UK lagoons and a stockpile. Initially, drying (105 °C) and screening (600 μm) were carried out, giving acceptable handling properties. Thereafter, processing using (63 μm) sieving, air classifying or grinding was investigated. The methods gave increased fineness levels (greatest with grinding), with some reductions in LOI also found after sieving and air classifying. Assessment of fly ash reactivity indicated improvements with processing, and most noticeable effects by grinding. Tests on concrete found that both consistence (slump) and compressive (cube) strength increased with processing and tended to follow fly ash fineness. Further analysis showed that strength could be related to the sub 10 μm particle level in fly ash. This appeared to be irrespective of processing method, with progressive increases (in strength) up to sub 10 μm contents of about 60% (maximum in the study). Concrete tests for water absorption and intrinsic (air) permeability, carbonation and chloride diffusion showed that these were also influenced by fly ash sub 10 μm content. The factors affecting behaviour are discussed and practical implications of the research considered.

AB - The paper describes a study carried out to explore the potential for recovery of fly ash from wet-storage areas for use as an addition in concrete, and involved drying and processing material to achieve finer fractions/reduce particle size. Three relatively coarse fly ashes with medium/high carbon contents (loss-on-ignition; LOI) were obtained from two UK lagoons and a stockpile. Initially, drying (105 °C) and screening (600 μm) were carried out, giving acceptable handling properties. Thereafter, processing using (63 μm) sieving, air classifying or grinding was investigated. The methods gave increased fineness levels (greatest with grinding), with some reductions in LOI also found after sieving and air classifying. Assessment of fly ash reactivity indicated improvements with processing, and most noticeable effects by grinding. Tests on concrete found that both consistence (slump) and compressive (cube) strength increased with processing and tended to follow fly ash fineness. Further analysis showed that strength could be related to the sub 10 μm particle level in fly ash. This appeared to be irrespective of processing method, with progressive increases (in strength) up to sub 10 μm contents of about 60% (maximum in the study). Concrete tests for water absorption and intrinsic (air) permeability, carbonation and chloride diffusion showed that these were also influenced by fly ash sub 10 μm content. The factors affecting behaviour are discussed and practical implications of the research considered.

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KW - Reactivity

KW - Sieving, air classifying and grinding

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EP - 215

JO - Cement and Concrete Composites

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SN - 0958-9465

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