| 種別 | Paper |
| 主題 | EFFECT OF STEEL REINFORCEMENT ON CONCRETE EXPANSION DUE TO ALKALI SILICA REACTION |
| 副題 | |
| 筆頭著者 | Ananda HERATH |
| 連名者1 | Taketo UOMOTO |
| 連名者2 | |
| 連名者3 | |
| 連名者4 | |
| 連名者5 | |
| キーワード | |
| 巻 | 10 |
| 号 | 2 |
| 先頭ページ | 843 |
| 末尾ページ | 848 |
| 年度 | 1988 |
| 要旨 | INTRODUCTION Alkali Aggregate Reaction is well known to denote a chemical reaction that involves alkali primarily derived from concrete pore solutions and certain types of reactive mineral constituents of aggregates. Several types of alkali aggregates reactions have been discovered including alkali silica reaction (ASR), details of which are given in the literature. Occurrence of this chemical reaction is partly due to the facts such as increase in alkali contents in cements due to various factors including use of economical cements manufacturing methods, use of higher cement contents of concrete in some applications and use of some kinds of aggregates with unknown service behavior. In 1940, the first papers recognizing the Alkali Aggregate Reaction were published by Stanton, and after that research has been undertaken to develop means of identifying the potentially reactive aggregates and reactive components in the cement paste. With regard to the reaction mechanism, it is well known that initially an alkaline silicate gel is formed which then imbibes water from the pore solution and increases in volume. If the increase in volume cannot be accommodated in surrounding porous space, swelling of the gel exerts expansive pressure that leads to cracking of concrete. Although there is an extensive literature to explain this reaction in plain concrete and mortars, there is lack of available data dealing with reinforced concrete members. It is very important to identity the adverse effects of ASR in RC members in order to maintain or rehabilitate the affected members. The effect of the presence of the steel reinforcing bars on the deterioration of the RC beams (columns), due to ASR, is presented in this paper. Several reinforced concrete specimens were cast, changing amount of reinforcement and alkali content, and cured in different curing conditions. The expansion, dynamic Young's modulus and weight change of each specimen were measured and steel strains monitored continuously. It was observed that the crack pattern in the reinforced concrete specimens was influenced by the rate of expansion and detailing of the reinforcements etc. Steel strains and concrete expansions showed a similar trend to each other as the reaction proceeds. From the data, it was concluded that the presence of reinforcing bars within the concrete contributes to restrict the expansion caused by ASR. CONCLUSIONS Within the scope of this investigation following conclusion can be drawn. 1. Cracks are formed between and approximately parallel to the steel reinforcing bars in RC beams and columns due to ASR. 2. Modulus of elasticity decreased with time and compressive strength remained constant. 3. Steel reinforcements embedded in concrete can restrain the expansion due to ASR. 4. Increase in steel percentage above a certain value has little effect on restraining ASR expansion. 5. Stirrups have little effect on restraining longitudinal expansion. 6. The bond characteristics of concrete and steel are not affected by ASR. |
| PDFファイル名 | 010-01-1150.pdf |