Evaluation of zeolite-bearing tuffs as pozzolanic additions for blended cements.

Four of the most widespread sedimentary zeolitic tuffs were tested to evaluate their pozzolanic character. The zeollitic tuffs were: a chabazite-phillipsite-rich tuff from Tufino(Naples, Italy), a phillipsite-rich tuff from Marano (Naples, Italy), a clinoptilolite-rich tuff from Esksehir (Anatolia, Turkey) and an erionite-rich tuff from Agua Prieta (Sonora, Mexico). Suitable tuff-lime mixtures were cured at room temperature and the reactivity data were collected in form of kinetic curves. All the tuffs showed a pozzolanic activity better than that reported for a typical pozzolan from Campi Flegrei (Naples), i.e. the volcanic glassy material precursor of the Neapolitan tuffs. Tuff reactivity was tentatively related to the microporosity of the zeolite components of the single tuffaceous materials. Zeolitic materials were also evaluated, investigating the behavior of blended cements was estimated according to the European Standards, using the so-called Fratini’s test, that allows to evaluate whether the material under investigation, regardless of its nature and mixture ratio, is able to combine with Ca(OH)2 produced by hydration of Portland clinker. Although this test was positive for most prepared blends, X-ray diffraction analysis demonstrated that the hardened pastes still contained residual amounts of Ca(OH)2 confined in the inner part of the manufacts.