Evaluation of the pozzolanicity of nanostructured sol-gel silica and silica fume by electrical conductivity measurement

•Nanostructured sol-gel silicas have high specific surface area.•The time for pozzolanic reaction is proportional to the total area of silica.•Surface area in very small pores become unavailable for reaction. The present paper evaluates the pozzolanic activity of two nanostructured silicas with high...

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Bibliographic Details
Published in:Construction & building materials 2018-01, Vol.160, p.252-257
Main Authors: Carneiro, Laísa R.S., Garcia, Dayana C.S., Costa, Michelle C.F., Houmard, Manuel, Figueiredo, Roberto B.
Format: Article
Language:English
Subjects:
Analysis
Electric properties
Electrical conductivity
Electrical conductivity variation measurements
Hydroxides
Measurement
Nanostructured silica
Pozzolanic reactivity
Silica fume
Silicon dioxide
Sol-gel method
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Summary:•Nanostructured sol-gel silicas have high specific surface area.•The time for pozzolanic reaction is proportional to the total area of silica.•Surface area in very small pores become unavailable for reaction. The present paper evaluates the pozzolanic activity of two nanostructured silicas with high specific surface area, synthetized by sol-gel technique, in comparison with silica fume. The materials were characterized by X -ray diffraction, scanning electron microscopy and nitrogen sorption. Electrical conductivity tests were performed in calcium hydroxide saturated solutions. Results revealed that both nanostructured sol-gel silicas have great pozzolanic reactivity, much higher than silica fume, especially in the early stage of the reaction. Hence, the pozzolanic reactivity of silica is affected by its specific surface area. Moreover, silica amount, test temperature and average pore size also seems to alter the silica reactivity. The reaction rate of silicas with small average pore size is reduced along the pozzolanic reaction.
ISSN:0950-0618
1879-0526
DOI:10.1016/j.conbuildmat.2017.11.042