Ceramics-Silikáty 51, (4) 217 - 224 (2007)

Original kaolin sand from deposit Vyšný Petrovec Slovakia, after temperature transformation provides burnt kaolin sand that contains metakaolin as a pozzolan. In order to verify potential efficiency of pozzolanic effect of its blend with ordinary Portland cement, the research oriented on the related cement-kaolin sand specimens was commenced. The relation between microstructural composition and compressive strength was studied. For this aim two types of kaolin sand with fractions 63- 36 µm and below 36 µm were used. The fraction 90-63 µm is not suitable for using in cement-burnt kaolin sand specimens. The optimal replacement of cement by burnt kaolin sand of 20, 30 and 40 wt. % was determined. The Portland cement-burnt kaolin sand blends contain between 4.10 and 14.48 wt.% of pure metakaolin. The strength of cement-burnt kaolin sand specimens depend slightly on the hydration products formed during hydration process of cement. The capability of pure metakaolin in burnt kaolin sand to combine with the most part of Ca(OH)₂ was confirmed by the X-ray diffraction analysis. The Ca(OH)₂ content is reduced due to pozzolanic reaction.