Pozzolanic activity of natural pozzolan-lime pastes and physicomechanical characteristics

In order to evaluate the pozzolanic activity of a natural pozzolan (NP) of rhyolitic composition, several pastes were prepared by mixing the pozzolan with hydrated lime, in different ratios. The pastes were stored in standard conditions (RH = 99 +/- 1%, T = 25 +/- 1 A degrees C) and evaluated using thermal analysis (TG-DTA), X-ray diffraction, compressive strength tests and mercury intrusion porosimetry, up to 270 days of curing. The obtained results showed that the compounds formed are CSH and C(4)ACH(11) (monocarboaluminate). The calcium hydroxide consumption increases as the initial amount of the natural pozzolan in the paste augments. As the NP/lime ratio increases, the open total porosity and total cumulative volume decrease, while the bulk density increases. The maximum strength development is obtained for NP/lime ratio of 2.