Characterization and Effects of Nanosilica on Consistency and Setting Times of Metakaolin Blended Cement Mortar
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Date
2021
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Abstract
The idea of sourcing for innovative construction Supplementary Cementitious
Materials (SCM) in concrete or mortar cannot be overemphasized. Metakaolin
has always been used to replace cement in concrete or mortar batching on site.
This research investigated the properties of factory produced blended cement
using metakaolin obtained from three different sources and consider effects of
nanosilica on blended cement mortar. The kaolin clay sourced from Ijero, Ikere,
and Isan in Ekiti states were calcined at 700 ˚C for 1 hour and thereafter, charac
terized using X-Ray Fluorescence Analyser (XRF) and X-Ray Diffraction Anal
ysis (XRD). Ordinary Portland Cement (OPC) clinker and 10% metakaolin were
used to produce blended cement. Liquid nanosilica was synthesized from cola
pod extract and silica precursor in ratio 1:5. A cement-sand ratio of 1:3 and
water/binder ratio of 0.5 were used to produce metakaolin blended cement mor
tar with addition of nanosilica in varying percentages of 1, 2, 3, 4 and 5% by
weight of the binder. The setting times and water demand of the blended cement
mortar were determined. The results revealed that the setting times and water
demand were observed to reduce as the percentage of nanosilica was increased to
a level of 4%. In addition, results of the XRF classified metakaolin as class N
pozzolans with the addition of SiO2, Al2O3, Fe2O3 greater than 70%. Also, the
SO3 for all the clay was found to be less than 4% and the peak intensities as re
flected on the XRD showing the amorphous nature of the silica.