種別(Category) 卒業論文  
Graduation thesis
タイトル(Title) 異なる鉱物組成を有するセメント硬化体のクリープ挙動
Creep Behavior of Cementitious Material Having Different Chemical Composition
著者(Author) Chong Chi Liong(マレーシア)
Chong Chi Liong(Malaysia)
主査(Supervisor) 石田哲也講師
Lecturer. ISHIDA Tetsuya
キーワード(Keyword)  
 
掲載誌(Events Venue) 東京大学卒業論文
Graduation thesis of the Univ. of Tokyo
発表年・月(Published Year, Month) 2003.3
論文入手先(Name of Publication) 東京大学図書館
Library of the Univ. of Tokyo
要旨(Abstract) Stress and deformation occur in young age concrete such as creep, thermal stress and shrinkage could cause initial defects and negatively affects long-term performance of the structures. In the case of massive concrete particularly, thermal stress may cause cracking and damage to the structure. Therefore, low heat cement heat is used to reduce the risk of cracking in massive concrete. However, there are other factors such as development of strength, self-shrinkage and creep which have to be investigated in order to predict the internal stress in the structure. In this research, strength development and creep of low heat cement is studied. Creep tests were conducted on mortar specimens made from ordinary and low heat Portland cement at various hydration-degree. It is found that at the growth of strength and stiffness with of both types of cement is similar when compared at the same hydration degree. Creep strain of both type of cements loaded at the same hydration degree were compared. The comparison showed no significant difference between them. It is understood that creep behavior of low heat cement is much influenced by its low rate of hydration. Analysis was made with DuCOM and compared with the experimental results. It is found that the program show acceptable prediction of creep at the higher hydration degree. However, creep is under-estimated by the program at low hydration degree. The reason is found to be the inaccuracy of strength prediction at low hydration degree. Deformation after unloading was observed to investigate the mechanism of creep. Considering creep to be caused by movement of water through micro-pore, it is expected it was expected that the creep recovery would be smaller with the increase of loading age. This is because the porosity of the cement paste decrease as hydration takes place and the recovery of water loss from gel would be more difficult. However, the results showed no significant correlation between creep recovery and the age of loading. The applied stress actually has effect on the creep recovery too. In this experiment, the effect of micro-pore structure on creep recovery could not be seen, as the specimens were loaded at different stress. Stiffness at the time of loading and unloading was measured separately using unloaded specimens. The recovery of the loaded specimens was observed to have a higher stiffness than the unloaded specimens. The explanation of this observation is that the applied load might have some effects on the hardening process of young age cement paste. However, experiment with higher accuracy need to be conducted to investigate this observation properly.