A comprehensive evaluation of sedimentary zeolites from Turkey as pozzolanic addition of cement- and lime-based binders S. Özen a,⇑ , M.C. Göncüog ˘lu b , B. Liguori c , B. de Gennaro c , P. Cappelletti d , G.D. Gatta e , F. Iucolano c , C. Colella c a Department of Industrial Design Engineering, Recep Tayyip Erdog ˘an University, Rize, Turkey b Department of Geological Engineering, Middle East Technical University, Ankara, Turkey c Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università Federico II, Napoli, Italy d Dipartimento di Scienze della Terra, Università Federico II, Napoli, Italy e Dipartimento di Scienze della Terra, Università degli Studi di Milano, Italy highlights  The speciﬁc surface area affects zeolite reactivity in the initial stages.  Si/Al ratio controls the pozzolanic activity at longer hydration times.  Among the exchanged forms, K + -clinoptilolite has the highest lime ﬁxation capacity.  Ability of lime ﬁxation does not always lead to a better mechanical behavior.  XRD is a more sensitive technique to detect reaction products than FTIR. article info Article history: Received 26 May 2015 Received in revised form 5 November 2015 Accepted 8 December 2015 Keywords: Natural zeolite Clinoptilolite Mordenite Analcime Pozzolanic activity Jander equation Zeolite-blended cement Compressive strength Microstructure abstract The pozzolanic action played by ﬁve natural zeolite-rich materials (three clinoptilolite- and one each mordenite- and analcime-bearing rocks) coming from Turkey, has been examined, evaluating also the inﬂuence of various chemical–physical parameters, such as grain size of the zeolitic materials and nature of the cation present as extra-framework component of the structure. Pozzolan activity has been esti- mated by the ofﬁcial test of the European Standards and by thermogravimetry, ﬁnding a good accordance between the two procedures. Clinoptilolite-rich rocks gave the best results, but performance turned out to depend on the speciﬁc surface area and pre-enrichment in a potassium form. Experimental data anal- ysis demonstrated that the pozzolanic reaction is kinetically controlled by the diffusion of reactants through a layer of dense reaction products. Experimental blended cements with the ﬁve zeolite-rich rocks were also prepared and the compressive strengths measured as a function of the curing time. The effec- tiveness of the pozzolanic action was monitored by XRD and FTIR analyses. An accurate microstructural study of the hardened pastes was also carried out and point analysis performed, pointing out that the zeolite-lime interaction is characterized by two stages: initially zeolite subtracts calcium from the envi- ronment by cation exchange, then it acts as a true pozzolan as soon as its structure breaks down. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction According to ASTM C125 deﬁnition [1], pozzolan is intended as ‘‘a siliceous and aluminous material which, in itself, possesses little or no cementitious value but which will, in ﬁnely divided form in the presence of moisture, react chemically with calcium hydrox- ide at ordinary temperature to form compounds possessing cementitious properties”. Pozzolans can be (1) naturally occurring products, such as vol- canic ash and pumice, zeolitic tuff and zeolites, (2) heat treated natural resources, e.g., metakaolin and rice husk ash, or (3) indus- trial by-products having different origins, such as silica fume and ﬂy ash. All these products are widely used in manufacturing blended cements, due to their ability to ﬁx portlandite, i.e., the detrimental free lime, Ca(OH) 2 , coming from the hydration reac- tion of Portland clinker. The partial replacement of clinker with pozzolan is gaining an increasing signiﬁcance, because of its bene- ﬁcial effect on (i) the reduction of CO 2 emission, (ii) energy-saving and (iii) enhancement of several technical features of the hardened http://dx.doi.org/10.1016/j.conbuildmat.2015.12.055 0950-0618/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: sevgi.ozen@erdogan.edu.tr (S. Özen). Construction and Building Materials 105 (2016) 46–61 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat