Properties of reactive magnesia-incorporated cements

Ardoğa, Mehmet Kemal
Magnesium oxide (MgO) has limited use in civil engineering applications. The presence of MgO (especially in free form) in portland cements is limited by the standards due to the risk involved in the gradual hydration of MgO that may lead to disruptive expansions after the cementitious system hardens. However, it is possible to overcome this detrimental effect by calcining magnesite at lower temperatures than that is encountered in the cement kilns and use thus obtained reactive MgO as an additive in cement. In this case, MgO will react with water to form magnesium hydroxide (brucite) while the cementitious system is still plastic. Later, brucite will carbonate to reform magnesium carbonates. In this study, firstly the synthesis of reactive magnesia from naturally – obtained magnesite was carried out at different calcination temperatures. Then the magnesia obtained was blended with CEM I and CEM II cements in varying amounts (15-50%, by mass). The cements thus obtained were studied comparatively with the control cements without reactive MgO from hydration reactions, strength, and durability characteristics points of view. It was found that the most reactive magnesia was obtained with the curing regime including 600 °C of burning temperature and 120 minutes of exposure time. It was also determined that the reactive magnesia caused a reduction in compressive strength when cured in ambient conditions. However, generally, when cured in a carbon dioxide environment, the compressive strengths increased with increasing carbon dioxide concentration.


Development of high temperature creep resistant aluminium based sand cast magnesium alloys
Yalınız, Emrah; Kalkanlı, Ali; Department of Metallurgical and Materials Engineering (2018)
The aim of this thesis is to develop alternative sand casting aluminum based magnesium alloys to substitute current sand castable helicopter transmission housing magnesium alloys such as ZE41A and EV31A. AZ91 magnesium alloy has also been preferred for helicopter transmission housing material. However, the lower creep resistance above 120 oC due to the presence of -(Mg17Al12) phase in the microstructure and showing varying mechanical properties in different section thicknesses limit the usage of AZ91 in th...
Production of fly ash-magnesium phosphate cements
Bilginer, Baki Aykut; Erdoğan, Sinan Turhan (null; 2019-05-02)
Magnezyum fosfat çimentolu (özellikle magnezyum potasyum fosfat çimentolu [MKPC]) bağlayıcılar Portland çimentosuna kısmi alternatif olabilecek sistemlerdir. MKPC yaygın olarak kalsine MgO tozu ve potasyum dihidrojen fosfat tuzu kullanılarak hazırlanır. Sulu karışımda meydana gelen asit-baz tepkimesi çok hızlı gerçekleştiğinden, bir geciktirici (boraks) de eklenir. MKPC’nin çabuk priz alma, çok hızlı dayanım kazanma ve yüksek nihai dayanım gibi geleneksel çimentolu sistemlere üstün yan...
Thermal degradation of polystyrene composites. Part I. The effect of brominated polyepoxy and antimony oxide
Kaya, Hatice; Hacaloğlu, Jale (2014-01-01)
Thermal degradation of polystyrene (PS) involving brominated polyepoxy (BA) and antimony oxide (PS/BE/Sb2O3) was studied systematically via direct pyrolysis mass spectrometry. Thermal decomposition of brominated polyepoxy was started by loss of end groups. The relative yields of high mass thermal degradation products of PS and the product distribution of brominated polyepoxy and antimony oxide were changed noticeably during the pyrolysis of PS/BE/Sb2O3 composite. Its thermal decomposition was initiated by t...
Development of polybenzimidazole/graphene oxide composite membranes for high temperature PEM fuel cells
Uregen, Nurhan; Pehlivanoglu, Kubra; Ozdemir, Yagmur; DEVRİM, YILSER (2017-01-26)
In this study, phosphoric acid doped Polybenzimidazole/Graphene Oxide (PBI/GO) nano composite membranes were prepared by dispersion of various amounts of GO in PBI polymer matrix followed by phosphoric acid doping for high temperature proton exchange membrane fuel cell (HT-PEMFC) application. The structure of the PBI/GO composite membranes was investigated by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and by thermogravimetric analysis (TGA). The introduction of GO into the FBI polymer matri...
Properties of reactive O-2 ion beam sputtered TiO2 on Si wafers
Ulucan, S; Aygun, G; Ozyuzer, L; Egilmez, M; Turan, Raşit (2005-02-01)
Tio(2) thin films were deposited on silicon (100) p-type wafers, using the reactive ion beam sputtering method in high vacuum as an alternative to conventional Argon ion beam sputtering in an O-2 environment. Oxygen ions with 1000 eV energy were formed in a thruster and bombarded a high purity Ti target. The molecules of Tio(2) were deposited on a Si (100) wafer at various substrate temperatures. The structural and optical properties were analyzed using Fourier Transform Infrared Spectroscopy in the range o...
Citation Formats
M. K. Ardoğa, “Properties of reactive magnesia-incorporated cements,” Ph.D. - Doctoral Program, Middle East Technical University, 2022.