A Multi-scale approach to characterization of volcanic natural pozzolans/

Sassani, Alireza
Three types of volcanic rocks, namely perlite, a zeolite-rich volcanic tuff and a feldspar-rich volcanic tuff were selected to represent the general group of Volcanic Natural Pozzolans (VNPs). The target group was those volcanic natural pozzolans which intrinsically possess pozzolanic properties, i.e. do not require heat-treatment to obtain pozzolanic reactivity. X-ray Fluorescence (XRF), Powder X-Ray Diffraction (XRD), Blaine air permeability test, Laser diffraction, thermogravimetry (TGA), solid-state 29Si nuclear magnetic resonance spectroscopy (NMR) and solidstate 27Al NMR techniques were utilized to characterize the unhydrated powder of the selected pozzolans. For each of the three selected VNPs the engineering performance of the respective 50 (wt%) VNP-50 (wt%) PC based system were evaluated. Mortar samples were studied for strength development and expansion due to Alkali-Silica reaction (ASR); while paste samples were studied by Isothermal Calorimetry method in order to monitor the heat evolution during the hydration. Pastes were then studied by the use of XRD, 29Si NMR, and 27Al NMR techniques vi so as to investigate the micro- and nano-structure of the hydration products of 50 (wt%)NP-50 (wt%)PC systems. The performance of the selected pozzolans with respect to pozzolanic activity and ASR expansion were almost similar; they all exhibited acceptable pozzolanic performance and ability to suppress ASR expansion. However, the pozzolans had different sources of pozzolanic reactivity, i.e. their pozzolanic property originate from different phases and/or is associated with different mechanisms. The C-S-H phases in the NP-blended pastes possessed longer silicate chains than the control samples. Aluminum incorporation into C-S-H structure was investigated and various Aluminum species were detected.
Citation Formats
A. Sassani, “A Multi-scale approach to characterization of volcanic natural pozzolans/,” M.S. - Master of Science, Middle East Technical University, 2014.