ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 58, (2) 138 - 144 (2014)


INFLUENCE OF POZZOLANA ADDITIVE ON PORTLAND CEMENT IN CHLORIDE AND SULFATE ENVIRONMENT AT LOW TEMPERATURE
 
Barauskas Irmantas, Kaminskas Rimvydas, Liaudanskyte Laima
 
Department of Silicate Technology, Chemical Technology Faculty, Kaunas University of Technology, Kaunas, Lithuania

Keywords: Portland cement, Pozzolana, Chloride, Sulfate, Friedel salt, Monocarboaluminate, Thaumasite
 

This study investigated the influence of natural pozzolana (opoka) additive on the hydration of Portland cement and the effects of chloride and sulfate ions on the formed hydrates under 4oC temperature. In the samples 5, 15 and 25 % (by weight) of the Portland cement was replaced with pozzolana additive - opoka. The specimens were cured in water at 20oC for 28 days. Then all samples were soaked in saturated NaCl solution at 4oC for 3 months. Later they were immersed into 5 % Na2SO4 solution and held there for 3 month at 4oC. All specimens were examined by thermal, X-ray diffraction and FT-IR analysis after every immersion in different solutions. It was estimated that under normal conditions opoka promotes the formation of calcium silicate hydrates and initiate the formation of monocarboaluminate. Monocarboaluminate affected by a saturated NaCl solution, becomes unstable and takes part in reactions producing Friedel salt at 4oC temperature. It was obtained, that opoka takes place in the pozzolanic reaction even at law temperature in a saturated NaCl solution. However, ettringite remained stable under the examined conditions and Thaumasite is mostly depends on decomposition of ettringite in 5 % Na2SO4 at 4oC temperature.


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