Research Information System
Thesis Type: Postgraduate
Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2019
Thesis Language: Turkish
Student: Buse BOZAN BEYDAĞI
Supervisor: Fatma Suna Balcı
Abstract:Calcium silicates are structures in hydrate and anhydrate form that take their diversity result from Ca/Si ratios close to each other. These highly porous structures, which are not economically produced in our country, are used in heat insulation due to their light weight and high mechanical strength, while they are used as shaped or semi-finished materials for fire protection due to their high thermal resistance. The most commonly used ones are tobermorite (Ca5Si6O16 (OH)2.5H2O) and xonotlite (Ca6Si6O17(OH)2) in hydrate form. In this study, the synthesis is done at different feed ratios (Ca/Si: 0.83-1.00) according to tobermorite and xonotlite phases and at different water/solid ratios (10 and 15). Pre-reaction process is done at different temperatures (40, 60 and 80oC) and different times (2 and 4 hour) and thereafter, with or without filtration, the synthesis was completed in an autoclave at 200oC at autogenous pressure. The obtained products are dried at room temperature, at 60oC in oven and at -110oC by freeze-drying technique. It is seen that, in thermal behavior of material, the removal of bound water and -OH starts after 250oC and becomes apparent after 300oC, and solid phase transformation occurs after 700oC. The calcination temperature is selected as 300oC and 700oC according to these phase transitions, and synthesis studies are carried out. Typical C-S-H crystal peaks which are detected by X-ray diffraction patterns, and the mass loss with the increase in feed ratio are seen for all materials. According to the results of FT-IR analysis, increasing preheating temperature and time and freeze-drying method cause intensifying of Si-O bonds. The success of product synthesis is supported by identifying the chemical structures of the phases with ICP-OES. As the calcium content increase, more adherent foil and fibril images are obtained according to TEM and SEM images. Thermal conductivity coefficients are found within the expected range (<0.065 W/m.K). The best results of synthesized products for both feed rates are obtained at the conditions of 80oC, 4 hours and freeze drying.