Analysing the Pozzolanic Reactivity of Chalcedony Dust in Cement Paste

The considerable energy consumption and greenhouse gas emissions in the production of Portland clinker makes it extremely important to use substitutes in the form of mineral additives. Chalcedony dust, being a natural mineral raw material, is an additive that may come into pozzolanic reaction, similarly as fly ash does. The present paper reports the results of research on the reactivity of chalcedony dust of variable graining. For the measurement of the degree of the pozzolanic reactivity of mineral additives, the physical methods according to Polish Standard PN-EN 450:1:2009, the Fratini mechanical testing method and the Italian method, were used. The employed methods revealed the properties of chalcedony pozzolanic dust of a grain size smaller than 0.063 mm. Tests for the effect of chalcedony dust on cement hydration were also carried out by the differential thermal analysis (DTA/TG) method. It was shown that the Ca(OH)(2) content was lower for cement pastes with mineral additive.