Title: Evaluation of Zeolite-Bearing Tuffs as Pozzolanic Addition for Blended Cements
Author(s): B. Liguori, D. Caputo, M. Marroccoli, and C. Colella
Publication: Symposium Paper
Appears on pages(s): 319-334
Keywords: Fratini's test; pozzolanic behavior; pozzolanic cements; pozzolanic materials; zeolitic tuffs
Four of the most widespread sedimentary zeolitic tuffs were tested to evaluate their pozzolanic character. The zeolitic tuffs were: a chabazite-phillipsite-rich tuff from Tufino (Naples, Italy), a phillipsite-rich tuff from Marano (Naples, Italy), a clinoptilolite-rich tuff from Eskisehir (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 prepared by mixing portland clinker, tuffs and gypsum. The pozzolanic behavior of the 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 the 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.