Journal of Scientific & In dustrial Research Vo l. 62, August 2003 , pp 809-8 12 Influence of Zeolite on the Mineralogical Properties Autoclaved Aerated Concrete Mustafa Albayrak Mineral Research and Exploration General Directorate (MTA), 06520, Turk ey and Turhan Ayyildiz* Ankara University, Faculty of Engineering, Department of Geolo gical Engineering, 06100 , Turk ey Received: I 0 December 2002; accepted:05 March 2003 Tob ermorite family to cement chemistry exhibits base exchange behavior. Zeolite (clinoptilolite) is synthesized for Al- substituted tobermorite (I I 0 A) , 90 J.llTI , instead of quartz around 50 °C for 4 h and autoclave at 200 °C produces sma ll er crystallites and ex hi bi ted larger radial pl atelet s. Tobermorite co ntent material show that bulk density increases sharply with decrease in AI. Bulk density values increase regularly with increase in compressive strength va lu es. Poro s it y diameter of the sa mples in crease with increases in quantity of aluminum, however, strength of material decreases. As a result, it is shown that use of clinoptilolite, instead of quartzite saves energy and has industrial app li ca ti o n. Keywords : Zeolite, Autoclaved aerated concrete, Concrete, Cement chemistry, Clinoptilolite, Tober morite, Min era logical properties Introduction Tobermorite is a hydrous calcium si li cate, which occurs as a platy mineral in calcium si li cate rocks. During steam curing, C-S-H aggregates are formed initially and later by reaction with dissolved si lica from quartz, tobermorite (5Ca0.6Si0 2 .5H 2 0) is formed as a main binder. Some workers have shown that the hydrothermal reactions in the Ca0-Si0 2 systems are controlled by the dissolution of quartz'- 2 . Tobermorite is technologically important because it is binding agent for autoclaved concrete. Megaw and Kelsey' have detennined the crystal structure of a naturally occurring tobermorite. It has been found that the tobermorite family, fundamental to cement chem istry can exhibit base exchange behaviour. Several Al-substituted tobermorites were synthesized with silica, kaolinite, and clinoptilolite4- 6 . Mitsuda and Taylor 7 have pointed out that with clinoptilolite (siliceous zeolite) the formation of tobermorite was fast. *For corresponden ce Email: ayyilidi z@e ng.ankara.edu.tr In this investigation the effect of AI on the formation of At-substituted tobermorite from C-S-H was investigated using clinoptilolite. Mineralogical and mecha nical properties of mate ri al with tobermorite are presented. Material and Methods Zeolite, used in this study, was obtained from Gordes (Manisa-Turkey) Zeolite Works. XRD ana ly ses were studi ed by Ri gaku Geiger Flex X-ray Diffractometer (MT A) and chemical analyses was determined by XRF technique (Rigaku RIX 3000 Spectrometer-MT A). Mineralogical analyses was also carried out by Scanning Electron Microscope ( SEM)- LEO 435 at Turkish Cement Cooperation. Considering the proportions of the raw mixtures, 2 · 8 · 9 block samples were prepared with mean ratio of Cai(AI+Si) = 0.48. In all the samples, clinoptilolite (90 11m) was used, in stead of quartz. Th e mjxtures were cast in a 16x4x4 em mold, hardened at atmospheric pressure at 50 °C for 4 h and later autoclaved at 200 °C und er saturated steam pressure of 11.5 bars for I 2 h.