A comparison of the specific surface area of fly ash measured by image analysis with conventional methods. (30th November 2018)

• Record Type: Journal Article
• Authors: Wang, Tiao; Ishida, Testuya; Gu, Rui
• Is Part Of: Construction & building materials. Volume 190(2018)
• Page Start: 1163
• Page End: 1172
• Publication Date: 2018-11-30
• Subjects: Specific surface area -- Fly ash -- Image analysis -- Laser diffraction -- Blaine air permeability -- Nitrogen absorption; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2018.09.131
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: Image analysis is suitable for determining the specific surface area of fly ash. Blaine air permeability test underestimates the specific surface area of fly ash. Nitrogen absorption test overestimates the specific surface area of fly ash. Laser diffraction test is affected by the material chemical composition. Laser diffraction test underestimates the specific surface area of porous fly ash. Abstract: The specific surface area (SSA) of fly ash has a significant effect on its pozzolanic reactivity and on the performance of fly ash-blended concrete. Because fly ash contains a considerable amount of irregularly shaped particles and unburned carbon, determination of an accurate SSA is analytically troublesome by conventional methods. Various methods for determining the SSA of fly ash are evaluated and compared in this study, including Blaine air permeability, nitrogen absorption testing, laser diffraction testing and image analysis. The experimental results show that Blaine air permeability and laser diffraction testing tend to underestimate the SSA of fly ash because they involve the assumption of perfectly spherical particle geometry. The SSA determined by nitrogen absorption testing is found to be associated with a significant overestimation induced by unburned carbon. Image analysis coupled with BSE appears to give consistent results and appears to be the most promising method of determining an accurate value for absolute SSA.