The Effect of Exposed Duration of High Temperature and Recovery Duration of Heat Release on the Normal Concrete with Fly Ash
| Autor: | Kuo, Ming-Feng, 郭銘峰 |
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| Rok vydání: | 1997 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 85 This study investigates the properties and behaviors of normal concretewith fly ash subjectd to elevated temperature. During the research,appropriatefly ash content,fly ash substitution method,and concrete mix design method are selected to find the reasonable proportions of normal concrete with fly ash.Large amount of samples are then produced from the reasonable proportions of normal concrete with fly ash,to test and to study the effects of "ExposedDuration of High Temperature" and "Recovery Duration of Heat Release" on the mechanical properties and behaviors of the concrete with fly ash.An analysison the elevated temperature properties and rehydration on concrete with fly ashis also conducted. The results show that under 400℃, concrete with fly ash revealed a contractingphenomenon.However, at 600℃,concrete expansion occurred due to the expansion ofsilicon aggregates,expansion is higher at 800℃.Unit weight of concrete show adecreasing trend along with the increase in exposed duration and temperature.Ultrasonic pulse-wave speed decreases with the increased in temperature and exposed duration.These revealed that voids and cracks increase in exposed duration.At 200℃∼400℃,dynamic modulus of elasticity of concrete with fly ash is larger then normal concrete.However at 600℃∼800℃,dynamic modulus of elasticity of normal concrete without fly ash is larger than concrete with fly ash. Compressivestrength at 200℃ is larger than at room temperature. Along with the increase intemperature and exposed duration, strength of concrete decreases.In terms of recoveringcondition after heat release,rehydration is best and strength recovery rate islargest under water recovery.The C-S-H formed by rehydration has a function offilling the voids and cracks as well as strength the matrix. Void Index Measurement(VIM) increased with the increase of exposed duration ofhighest temperature.Void index of concrete with fly ash is relatively smaller thannormal concrete without fly ash.However,at 600℃ ∼800℃,void index of concretewith fly ash is relatively larger than normal concrete without fly ash.Generallyspeaking,elevated temperature resistance of normal concretewith fly ash is notbetter than normal concrete without fly ash. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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