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PESİMUM REAKTİF AGREGA İÇERİĞİNİN ALKALİ-SİLİKA REAKSİYONUNA ETKİSİNİN DENEYSEL YÖNTEMLERLE ARAŞTIRILMASI

THE INVESTIGATION OF EFFECTS OF PESSIMUM REACTIVE AGGREGATE CONTENT ON ALKALI-SILICA REACTION WITH EXPERIMENTAL METHODS

Journal Name:

  • İstanbul Yerbilimleri Dergisi

Publication Year:

  • 2004

Key Words:

Keywords (Original Language):

Author NameUniversity of AuthorFaculty of Author
Abstract (2. Language): 
The reactive aggregate content in concrete or mortar affects the expansion generated from alkali silica reaction (ASR). In this study, to investigate the reactive aggregate percentage in the bulk of the aggregate causing maximum expansion (were known as Pessimum ratio in literature), a series of laboratory tests was carried out and their results were compared. Five different reactive aggregate types such as opal, chert, chalcedony, andesite and basalt were identified through petrographical examination. Their reactivity was determined by gel pat and chemical tests, and some additional tests were performed to determine the physical and mechanical properties of these reactive aggregate. In the laboratory, mortar bars having different reactive aggregates percentages were prepared and the amount of reactive aggregate causing the maximum expansion of the mortar bars was determined. When the bulk of aggregate contains 20% opal which is the aggregate with the highest reactivity, maximum expansion was observed. The Pessimum reactive aggregate content for chert, chalcedony, andesite and basalt were determined as 40%, 50%, 80% and 100%, respectively. At the end of accelerated mortar bar tests, thin sections for fluorescent microscopy studies were prepared using the cubic samples extracted from mortar bars. As a result of the fluorescent microscopy studies on thin sections, the maximum silica gel sourced from ASR was observed if the reactive aggregate content was around Pessimum ratio. This is the second important result obtained from microscopy studies that distinct alkali silica gels developments were observed in different reactive aggregates. However, while silica gel rims around opal were observed, silica gels throughout micro cracks in chert were evident. In chalcedony aggregates, fibrous type alkali silica gel developments were observed.
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Abstract (Original Language): 
Harç veya beton içinde kullanılan agregaların amorf silis içeriği, alkali silika reaksiyonu nedeni ile meydana gelen hacimsel genleşme miktarını etkilemektedir. Bu çalışmada, harçta en fazla genleşmeye neden olan ve literatürde pesimum oranı olarak adlandırılan tüm agrega içindeki reaktif agrega oranını araştırmak için çeşitli deneyler yapılmış ve bunların sonuçları birbirleriyle karşılaştırılmıştır. Petrografik çalışmalarla tanımlanan, mekanik ve fiziksel özellikleri belirlenen opal yumrusu, çört, kalsedon yumrusu, andezit ve bazalt türü beş farklı reaktif agreganın alkali reaktiviteleri jel pastası (Jel-pat) ve kimyasal yöntemle saptanmıştır. Reaktif agregalar farklı oranlarda tüm agrega içine katılarak harç çubukları hazırlanmış ve hızlandırılmış harç çubuğu deneyleri gerçekleştirilmiştir. En fazla boyca uzamanın meydana geldiği pesimum reaktif agrega oranı belirlenmiştir. Çalışma kapsamı içinde yapılan deneylerde diğerlerine göre daha yüksek alkali reaktivitesi gösteren opal yumrusu, tüm agrega içinde %20 oranında bulunduğunda en fazla genleşme meydana gelmektedir. Çört, kalsedon yumrusu, andezit ve bazaltın pesimum oranları ise sırasıyla %40, %50, %80 ve %100 olarak belirlenmiştir. Hızlandırılmış harç çubuğu deneyleri sonunda, harç çubuklarından küp örnekler alınmış ve bunlardan floresans mikroskop inceleme tekniğine uygun ince kesitler hazırlanmıştır. İnce kesitler üzerinde yapılan floresans mikroskop çalışmaları sonucunda, reaktif agregalar çevresinde en fazla alkali silika jel gelişiminin pesimum oranlarında meydana geldiği gözlemlenmiştir. Mikroskop incelemeleri sırasında gözlemlenen diğer bir olgu da, reaktif agregaların çeşidine göre alkali silika jel gelişimlerinin farklı olmasıdır. Opal türü agregalar çevresinde haleleler şeklinde alkali silika jel gelişirken, çörtte kılcal çatlaklar boyunca, kalsedonda ise lif lif ayrılmalar şeklinde alkali silika jel gelişimleri saptanmıştır.
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  • 2
119-128
  • Turkish

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