The İnvestigation of Metakaolin Effect on Concrete and Mortars Made with Agregates İncluding Reactive Silica

Abstract

In the production of concrete and ferroconcrete elements, the usage of pozzolanic industrial wastes such as fly ash (FA), silica fume (SF), blast furnace slag (GBS) and metakaolin (MK) has a successful background. High- reactivity metakaolin(MK) is a manufactured pozzolan produced by thermal processing of purified kaolinitic clay. In this study, in concrete and mortars made with aggregates including alkali-silica, the metakaolin effect, pozzolanic activity experiment, concrete pressure strength were investigated by alkali- silica reaction (ASR) experiments affecting the durability in concrete and mortars. As a result of puzzolanic activity experiment, it is provided pressure strength at the rate of 95% (0.95) for a 28-day value. In the results of Accelerated mortar bar experiment, the formation of alkali silica reaction (ASR) affecting concrete strength was made harmless by the use of metakaolin at certain rates. In the samples with the additive at the rates of 10, 15 and 20%, the formation of alkali- silica reaction (ASR) was seen to fall below the limit of 0,10% that is a standard value. At the end of experiment time, control sample becomes "secure amount" in which minimum additive amount that reduces alkali- silica reaction dilatations below the value of 0.10% can be used. According to pressure strength results, it was detected that the usage of metakaolin (MK) positively affected the mechanical features of the concrete, increased the strength and improved the creep and permeability properties of the concrete. Ideal additive amount must be 10% in terms of the formation of ASR and pressure strength. Being ceased of the puzzolanic additives to be wastes and spreading its usage in terms of contributing to the economy will be suitable. In the concretes prepared with true mixtures, multi-dimensional acquisitions will be achieved in terms of strength and this will prolong the service durability of concrete structures. 

Keywords

• Metakaolin
• Alkali-Silica Reaction
• Puzzolanic Activity Experiment
• Expansion
• Industrial Waste

Reaktif Silis İçeren Agregalarla Yapılan Beton ve Harçlarda Metakaolin Etkisinin Araştırılması

Öz

Beton ve betonarme elemanların üretiminde uçucu kül (UK), silis dumanı (SD), yüksek fırın cürufu (YFC) ve metakaolin (MK) gibi puzzolanik endüstriyel atıkların kullanımının başarılı bir geçmişi vardır. Yüksek reaktivite metakaolin (MK), saflaştırılmış kaolinitik kilin ısıl işlem ile üretilen bir puzolandır. Bu çalışmada alkali silis içeren agregalarla yapılan beton ve harçlarda, mineral katkı olan metakaolin etkisi; puzolanik aktivite deneyi, beton basınç dayanımı, beton ve harçlarda dayanımı etkileyen alkali silika reaksiyonu deneyleri ile araştırılmıştır.

Puzolanik aktivite deneyi sonucunda 28 günlük değer olarak % 95 (0.95) oranında basınç dayanımı sağlamıştır. Hızlandırılmış harç çubuğu deneyi sonuçlarında metakaolinin belirli oranlarda kullanımıyla beton dayanımını etkileyen alkali silika reaksiyonu (ASR) oluşumu zararsız hale getirilmiştir. Metakaolin katkılı olarak hazırlanan %10,15 ve 20 oranında katkılı numunelerde alkali silika reaksiyonu oluşumu standart değer olan 0,1 sınırının altına indiği görülmüştür. Deney süresi sonunda kontrol numunesi alkali silika reaksiyonu genleşmelerini %0.1 değerinin altına düşüren minimum katkı miktarı kullanılabilecek “emniyetli miktar” olmaktadır.

Basınç dayanımı sonuçlarına göre, metakaolin (MK) kullanımı betonun mekanik özelliklerini olumlu etkilediği, dayanıklılığı arttırdığı, betonda sünme ve geçirimlilik özelliklerini iyileştirdiği tespit edilmiştir. ASR oluşumu ve basınç dayanımı açısından ideal katkı miktarının %10 olması yeterlidir.

Puzzolanik katkıların atık olmaktan çıkması, ekonomiye fayda sağlaması açısından kullanımının yaygınlaşması uygun olacaktır. Doğru karışımlarla hazırlanan betonlarda dayanıklılık yönünden çok yönlü kazanımlar elde edilecek, buda betonarme yapıların servis ömrünü uzatacaktır.

Anahtar Kelimeler

• Metakaolin
• Alkali-Silica Reaction
• Puzzolanic Activity Experiment
• Expansion

Kaynakça

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