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Metakaolin sand–blended-cement pastes: Rheology, hydration process and mechanical properties
In the present work, the use of three Slovak poor metakaolin sands with different metakaolin content (36.0% (MK-1), 31.5 (MK-2) and 40.0% (MK-3)) and specific surface has been deeply studied as mineral addition for Portland cement. The percentage of metakaolin sands in the blended cements was 10%, 2...
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Published in: | Construction & building materials 2010-05, Vol.24 (5), p.791-802 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | In the present work, the use of three Slovak poor metakaolin sands with different metakaolin content (36.0% (MK-1), 31.5 (MK-2) and 40.0% (MK-3)) and specific surface has been deeply studied as mineral addition for Portland cement. The percentage of metakaolin sands in the blended cements was 10%, 20% and 40%.
The pozzolanic tests confirm that the three metakaolin sands show a high pozzolanic activity, comparable to a commercial metakaolin and silica fume. With respect to the rheological behaviour, metakaolin sand–blended-cement pastes fit to Herchel–Bulkley model and their yield stress increases as the metakaolin content increases. MK-3 sand with the highest pozzolanic activity and highest specific surface induces the highest increase of the yield stress.
From the calorimetric results it is concluded that the addition of MK-1 and MK-2 sands to Portland cement induces a delay up to 2
h of the precipitation of the main hydration products in the blended-cement pastes and decreases the maximum heat evolution rate. On the contrary, the incorporation of 40% of MK-3 sand shortens 6
h its apparition and increases significantly the maximum heat evolution rate. Additionally, the presence of the metakaolin sands reduces the heat released during the hydration process with respect to non-blended-cement pastes.
The incorporation of metakaolin sand induces a decrease of the mechanical strength, being the decrease higher as the metakaolin sand content increases although they also produce a refinement in the pore structure and a decrease of the permeability. |
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ISSN: | 0950-0618 1879-0526 |
DOI: | 10.1016/j.conbuildmat.2009.10.028 |