Pozzolanic activity of natural zeolites

Özen, Sevgi
The mineralogical properties and the effects of different zeolitic tuffs (clinoptilolites from Gördes, Bigadiç and Aliağa; mordenite from Foça and analcime from Ayvacık, western Turkey) on pozzolanic activity were investigated. The detailed mineralogical, chemical and physical characterization was followed by investigation of the physical and chemical factors that control the pozzolanic reaction in lime-pozzolan pastes in 3 to180 days. For this, thermogravimetric analyses and Fratini’s tests were applied. Experiments showed that higher specific surface area enhances the pozzolanic activity at the initial stage but it has no significant effect on reactions thereafter. The main effect of Si/Al ratio was observed at later stages, especially after 28 days. Clinoptilolite-rich tuffs exchanged with K+ display faster reaction rates than Ca2+ and Na+-exchanged ones at longer periods. The second part of the study covers characterization of crystalline hydration products of hardened pastes as well as compressive strength behavior of blended cement mortars containing zeolitic tuffs as replacement of Portland cement. Furthermore, morphological, chemical and microstructural properties of hydrated cement products were examined. Decreasing intensity of zeolitic peaks on XRD patterns confirms the dissolution of zeolites and their involvement in pozzolanic reactions. Based on the experimental results, the compressive strength of clinoptilolite-rich tuff from Bigadiç exhibited excellent strength performance, which is approximately 10% higher than that of control Portland cement at 28 days of hydration. The compressive strength of clinoptilolite-rich tuff from Gördes is slightly higher than the control cement. It is confirmed that high strength performance should not be only considered with regard to their ability to fix lime. Physical parameters on sample preparation have also important controls on strength e.g. by arrangement of the porosity.
Citation Formats
S. Özen, “Pozzolanic activity of natural zeolites,” Ph.D. - Doctoral Program, Middle East Technical University, 2013.