LONG-TERM PROPERTIES OF CEMENT COMPOSITES WITH VARIOUS METAKAOLINITE CONTENT

The optimal temperature of transformation of kaolin sand to metakaolin sand (MKS), resulting in complete conversion of kaolinite to pozzolanic active metakaolinite (MK), is 650 C over a period of 1 h. To obtain information on the mechanism of the pozzolanic reaction in the studied binary system, cem...

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Bibliographic Details
Published in:Ceramics (Praha) 2013-01, Vol.57 (1), p.74-81
Main Authors: Krajci, L, Janotka, I, Puertas, F, Palacios, M, Kuliffayova, M
Format: Article
Language:English
Subjects:
Cement paste
Cements
Compressive strength
Kaolin sand
Metakaolin
Pastes
Phase composition
Pore structure
Porosity
Portland cements
Process control
Sand
Transformations
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Summary:The optimal temperature of transformation of kaolin sand to metakaolin sand (MKS), resulting in complete conversion of kaolinite to pozzolanic active metakaolinite (MK), is 650 C over a period of 1 h. To obtain information on the mechanism of the pozzolanic reaction in the studied binary system, cement pastes with two MKS at a substitution level of Ordinary Portland cement (OPC) with MKS by 10, 20 and 40 wt%, corresponding to 3.6-16.0% MK content in the pastes, were tested. The pozzolanic reaction of MK with hydrating OPC was confirmed by XRD and thermal analyses. This process, accompanied by a gradual reduction in Ca(OH)2 content, was the most intense in pastes with the highest MK contents (14.4 and 16.0%). A decrease in the micropore and total pore volume until the MK content in paste of 7.2% is a measure of pore structure improvement, specified as pore structure refinement. For MK contents up to 8.0%, the micropore portion with a pore radius < 10 nm rises and that with a pore radius in the range between 10 and 100 nm declines. Resulting compressive strengths of related cement pastes with various MK content were comparable with the strengths of pastes without MK. The obtained results confirmed that MKS is a promising additive for prospective blended cements.
ISSN:0862-5468
1804-5847