Calorimetric evolution of the early pozzolanic reaction of natural zeolites

The pozzolanic reaction between natural zeolite tuffs, portlandite and water was investigated over the course of the early reaction period up to 3 days. Isothermal conduction calorimetry experiments supplemented by TG/DTG and XRD analyses assisted in the elucidation of the sequence of reaction processes taking place. The calorimetry experiments clearly showed the dependence of the pozzolanic reaction rate and associated heat release on the fineness of the zeolite tuff. Higher external surface areas of pozzolans yield higher total heat releases. Also the exchangeable cation content of the zeolites influences the reaction rate. Release of exchangeable alkalis into solution promotes the pozzolanic reaction by raising the pH and zeolite solubility. The appearance of an exotherm after approximately 3 h of reaction is more conspicuous when alkali-rich zeolites are reacted. This exotherm is conceived to be related to a transformation or rupture of initially formed reaction products covering the zeolite grains. The formation of substantial amounts of ‘stable’ calcium silicate hydrate (C–S–H) and calcium aluminate hydrate (C–A–H) reaction took place after an induction period of more than 6 h. The openness of the zeolite framework affects the proneness of the zeolite to dissolution and thus its reactivity. Open framework zeolites such as chabazite were observed to react much more rapidly than closed framework zeolites such as analcime.

[1]  Kristin Vala Ragnarsdottir,et al.  Dissolution Kinetics of Heulandite at pH 2-12 and 25 C , 1993 .

[2]  N ChanSY,et al.  高性能ゼオライト,シリカヒューム,及びPFAコンクリートの初期表面吸着及び塩化物拡散の比較研究 , 1999 .

[3]  Sammy Chan,et al.  Comparative study of the initial surface absorption and chloride diffusion of high performance zeolite, silica fume and PFA concretes , 1999 .

[4]  Nasser Y. Mostafa,et al.  Heat of hydration of high reactive pozzolans in blended cements: Isothermal conduction calorimetry , 2005 .

[5]  L. Lam,et al.  A study on the hydration rate of natural zeolite blended cement pastes , 1999 .

[6]  R. Snellings,et al.  Pozzolanic reactions of common natural zeolites with lime and parameters affecting their reactivity , 2009 .

[7]  Sadaaki Yamamoto,et al.  Dissolution of Zeolite in Acidic and Alkaline Aqueous Solutions As Revealed by AFM Imaging , 1996 .

[8]  P. Joyce,et al.  Pozzolanic reactivity of the supplementary cementitious material pitchstone fines by thermogravimetric analysis , 2009 .

[9]  I. Janotka,et al.  Sulphate resistance and passivation ability of the mortar made from pozzolan cement with zeolite , 2008 .

[10]  S. Alonso,et al.  Calorimetric study of alkaline activation of calcium hydroxide–metakaolin solid mixtures , 2001 .

[11]  J. Dweck,et al.  Thermogravimetry on calcined mass basis — hydrated cement phases and pozzolanic activity quantitative analysis , 2009 .

[12]  M. Frías,et al.  Pozzolanic reaction of a spent fluid catalytic cracking catalyst in FCC-cement mortars , 2007 .

[13]  John Bensted,et al.  Structure and Performance of Cements , 2001 .

[14]  A. Chatterji,et al.  Hydration of Portland Cement , 1965, Nature.

[15]  F. Glasser,et al.  Hydration of cements based on metakaolin: thermochemistry , 1990 .

[16]  R. Snellings,et al.  The zeolite–lime pozzolanic reaction: Reaction kinetics and products by in situ synchrotron X-ray powder diffraction , 2009 .

[17]  W. Roszczynialski.  Determination of pozzolanic activity of materials by thermal analysis , 2002 .

[18]  Viktor Gutmann,et al.  The Donor-Acceptor Approach to Molecular Interactions , 1978 .

[19]  Moisés Frías,et al.  The pozzolanic activity of different materials, its influence on the hydration heat in mortars , 1996 .

[20]  A. Hellawell,et al.  The hydration of Portland cement , 1978, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[21]  F. Liebau,et al.  Structural Chemistry of Silicates: Structure, Bonding, and Classification , 1985 .

[22]  J. F. Young,et al.  The hydration of tricalcium silicate in the presence of colloidal silica , 1984 .