新澆置再生混凝土受震擾動後之強度研究

The Effects of Vibration on the Strength of Newly Poured Concrete Using Recycled Aggregate

莊惠丞(Hui-Cheng Zhuang)

指導教授 ： 張子修

朝陽科技大學/理工學院/營建工程系/碩士(2009年)

摘要

摘 要
本研究試驗使用營建廢棄物之新澆置混凝土在一定時間內受到不同程度之震動。實驗結果顯示在弱震擾動下其折減率為21%～30%；中震擾動其折減率為23%～32%；強震擾動其折減率為24%～34%；劇震擾動其折減率為28%～37%。
本研究發現新澆置混凝土試體在"臨界時間點"內受震擾動後會導致其抗壓強度嚴重折減，本研究亦發現當震動級數為弱震、中震、強震、劇震時，其"臨界時間點"約分別為70分鐘、90分鐘、120分鐘、140分鐘，研究初步推論臨界時間點上限約為150分鐘，在此時間以內產生各級地震對混凝土強度影響極大。
本研究亦發現新澆置混凝土試體當震動發生在"微折減時間點"後，則震動對混凝土圓柱試體強度影響應極為輕微。當地震強度為弱震、中震、強震、劇震時，其"微折減時間點"分別為450分鐘、520分鐘、590分鐘、660分鐘，而微折減時間點上限約為680分鐘，此研究結果可初步推論約12小時(720分鐘)後各級震動對使用營建廢棄物之新澆置混凝土強度影響已相當輕微。

關鍵字

地震工程 ； 強度折減 ； 混凝土 ； 再生骨材

並列摘要

Abstract
The research was conducted to study the effect of vibration on the strength of concrete using recycled aggregates. The specimens were subjected to a series of pre-determined vibration effects (25 gal, 70 gal, 190 gal, 718gal) at selected time periods (15 minutes, 30 minutes, 1 hr, 10 hr, 20hr) after the concrete was mixed. In general, the results of the study exhibit that reduction of the 28-day strength of the concrete are 21-30%,23-32%, 24-34%, and 28-37% for the vibration equivalent to minor, moderate, strong, and devastating earthquake, respectively.
The results of the study also revealed that vibration introduces much more significant influence on the reduction of the concrete strength when the vibration was applied within a “critical time period” after the concrete was poured, and after which the influence becomes much less. The results indicated that the “critical time period” is about 70, 90, 120, and 140 minutes for the same series of vibration effects mentioned above. A preliminary conclusion was reached based on the test results that, the upper limit of the critical time is about 150 minutes (2-1/2 hrs), within which all levels of vibration effect introduce severe reduction of strength up to 30% compared with that subjected to no vibration.
The study results also revealed that vibration introduces very little effect on the strength of concrete beyond a certain time period after the concrete was mixed which is defined as the “minimal effect time period”. According to the test results, for specimens subjected to vibration effect equivalent to minor, moderate, strong, and devastating earthquake, the “minimal effect time period” was revealed to be 450, 520, 590, and 660 minutes respectively. It is preliminarily concluded that the upper limit of the “minimal effect time period” is about 720 minutes (12 hours) after which all levels of vibration effects introduce very little or no effect on the strength of the concrete with a reduction ratio less than 4%.

並列關鍵字

concrete ； recycled aggregate ； vibration effect ； earthquake engineering

參考文獻

參考文獻

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