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The Effect of Fly Ash Microspheres on the Pore Structure of Concrete

Department of Mechanics of Materials and Structures, Faculty of Civil and Environmental Engineering, Gdansk University of Technology, Narutowicza 11/12, 80–233 Gdansk, Poland
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Minerals 2020, 10(1), 58; https://doi.org/10.3390/min10010058
Received: 10 December 2019 / Revised: 6 January 2020 / Accepted: 7 January 2020 / Published: 9 January 2020
The fly ash microspheres (FAMs) formed during the mineral transformation stage in coal combustion are hollow spherical particles with a density less than water. This paper presents the results of X-ray micro-computed tomography and an automatic image analysis system of the porosity in the structure of hardened concrete with microspheres. Concrete mixtures with ordinary Portland cement and two substitution rates of cement by microspheres—5% and 10%—are investigated. For all considered mixes, a constant water/binder ratio (w/b) equal to 0.50 was used. The distribution of the air voids and the compressive strength of the concrete were tested after 28 days. With the increasing mass of cement replacement by FAMs, the compressive strength decreases after 28 days. The total volume of the air voids in hardened concrete with fly ash microspheres tested by X-ray varies from 5.1% to 7.4%. The closed pores constitute more than 80% of the total content of air pores. The study proves that the use of microspheres grains with specific dimensions has a significant impact on concrete porosity. Their application in concrete technology can be an alternative aeration solution for fresh concrete mixes and an effective method for utilization.
Keywords: fly ash microspheres; air voids structure; concrete; X-ray computed tomography fly ash microspheres; air voids structure; concrete; X-ray computed tomography
MDPI and ACS Style

Haustein, E.; Kuryłowicz-Cudowska, A. The Effect of Fly Ash Microspheres on the Pore Structure of Concrete. Minerals 2020, 10, 58.

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