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Title: Alkali-activation potential of biomass-coal co-fired fly ash

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Journal Article: Publisher's Accepted Manuscript
Journal Name:
Cement and Concrete Composites
Additional Journal Information:
Journal Volume: 73; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-10-04 21:41:11; Journal ID: ISSN 0958-9465
Country of Publication:
United Kingdom

Citation Formats

Shearer, Christopher R., Provis, John L., Bernal, Susan A., and Kurtis, Kimberly E. Alkali-activation potential of biomass-coal co-fired fly ash. United Kingdom: N. p., 2016. Web. doi:10.1016/j.cemconcomp.2016.06.014.
Shearer, Christopher R., Provis, John L., Bernal, Susan A., & Kurtis, Kimberly E. Alkali-activation potential of biomass-coal co-fired fly ash. United Kingdom. doi:10.1016/j.cemconcomp.2016.06.014.
Shearer, Christopher R., Provis, John L., Bernal, Susan A., and Kurtis, Kimberly E. Sat . "Alkali-activation potential of biomass-coal co-fired fly ash". United Kingdom. doi:10.1016/j.cemconcomp.2016.06.014.
title = {Alkali-activation potential of biomass-coal co-fired fly ash},
author = {Shearer, Christopher R. and Provis, John L. and Bernal, Susan A. and Kurtis, Kimberly E.},
abstractNote = {},
doi = {10.1016/j.cemconcomp.2016.06.014},
journal = {Cement and Concrete Composites},
number = C,
volume = 73,
place = {United Kingdom},
year = {Sat Oct 01 00:00:00 EDT 2016},
month = {Sat Oct 01 00:00:00 EDT 2016}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.cemconcomp.2016.06.014

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  • Current US national standards for using fly ash in concrete (ASTM C618) state that fly ash must come from coal combustion, thus precluding biomass-coal co-firing fly ash. The co-fired ash comes from a large and increasing fraction of US power plants due to rapid increases in co-firing opportunity fuels with coal. The fly ashes include coal fly ash, wood fly ash from pure wood combustion, biomass and coal co-fired fly ash SW1 and SW2. Also wood fly ash is blended with Class C or Class F to produce Wood C and Wood E. Concrete samples were prepared with fly ashmore » replacing cement by 25%. All fly ash mixes except wood have a lower water demand than the pure cement mix. Fly ashes, either from coal or non coal combustion, increase the required air entraining agent (AEA) to meet the design specification of the mixes. If AEA is added arbitrarily without considering the amount or existence of fly ash results could lead to air content in concrete that is either too low or too high. Biomass fly ash does not impact concrete setting behaviour disproportionately. Switch grass-coal co-fired fly ash and blended wood fly ash generally lie within the range of pure coal fly ash strength. The 56 day flexure strength of all the fly ash mixes is comparable to that of the pure cement mix. The flexure strength from the coal-biomass co-fired fly ash does not differ much from pure coal fly ash. All fly ash concrete mixes exhibit lower chloride permeability than the pure cement mixes. In conclusion biomass coal co-fired fly ash perform similarly to coal fly ash in fresh and hardened concrete. As a result, there is no reason to exclude biomass-coal co-fired fly ash in concrete.« less
  • This study presents measurements of airborne concentrations of respirable crystalline silica in the breathing zone of workers who were anticipated to encounter coal fly ash. Six plants were studied; two were fired with lignite coal, and the remaining four plants used bituminous and subbituminous coals. A total of 108 personal breathing zone respirable dust air samples were collected. Bulk samples were also collected from each plant site and subjected to crystalline silica analysis. Airborne dust particle size analysis was measured where fly ash was routinely encountered. The results from bituminous and subbituminous fired plants revealed that the highest airborne flymore » ash concentrations are encountered during maintenance activities: 0.008 mg/m{sup 3} to 96 mg/m{sup 3} (mean of 1.8 mg/m{sup 3}). This group exceeded the threshold limit values (TLV) in 60% of the air samples. During normal production activities, airborne concentrations of crystalline silica ranged from nondetectable to 0.18 mg/m{sup 3} (mean value of 0.048 mg/m{sup 3}). Air samples collected during these activities exceeded the current and proposed TLVs in approximately 54% and 65% of samples, respectively. Limited amounts of crystalline silica were detected in samples collected from lignite-fired plants, and approximately 20% of these air samples exceeded the current TLV. Particle size analysis in areas where breathing zone air samples were collected revealed mass median diameters typically between 3 {mu}m and 8 {mu}m. Bulk and air samples were analyzed for all of the common crystalline silica polymorphs, and only alpha quartz was detected.« less
  • Trace elements were extracted from a coal-fired power plant electrostatic precipitator ash with nitric acid, hydrochloric acid, citric acid, redistilled water, and ammonium hydroxide as extractants. Effluent waters at this plant were sampled to assess the elevation of trace element concentrations compared with intake waters. The results showed a positive correlation between those elements most extractable by water (B, F, Mo, and Se) or acid (As, B, Cd, F, Mo, and Se) and those elements most elevated in effluent waters (As, B, F, Mo, and Se).
  • Sulphur retention depends on the alkaline metal oxide content of the fly ash. Correlations between retention and the relative concentrations of specific alkaline metal oxides are closer for boilers with similar combustion characteristics and particulate collection systems.