Investigation of the pozzolanic activity of microwave heat-treated kaolin

Abstract

Different methods are used to increase the pozzolanic activity of clay. Muffle or rotary furnaces consume significant amount of energy and require long time for calcination. Microwave technology has potential to be an alternative for the calcination of clays. In this study, the effect of short-term microwave heat treatment on the pozzolanic activity of kaolin was investigated. For this purpose, the strength activity index of the kaolins, which were heat treated at 300, 450, 600 and 800 watts for 10 minutes in a household type microwave oven, were determined. The results were compared with kaolins calcined in the muffle furnace at 600, 700 and 800°C for 1, 3 and 5 hours. The 28-day strength activity index of the kaolins calcined in the muffle furnace varied between 82.5-107.9%, and this value was in between 74.3-80.5% for the microwave heat-treated kaolins. The strength activity index of microwave heat-treated kaolins, being 4.6-13.3% higher than that of the raw kaolin, showed the potential of the microwave heat treatment for calcination.

Keywords

• Kaolin
• Metakaolin
• Calcination
• Microwave
• Compressive strength

Mikrodalga ısıl işlemi uygulanan kaolinin puzolanik aktivitesinin incelenmesi

Öz

Kilin puzolanik aktivitesinin arttırılması amacıyla farklı yöntemler kullanılmaktadır. Kül fırını ve döner fırınlarda yapılan kalsinasyon hem kayda değer miktarda enerji harcamakta hem de uzun süre almaktadır. Mikrodalga teknolojisi, killerin kalsinasyonu için alternatif olma potansiyeli taşımaktadır. Bu çalışmada kısa süreli mikrodalga ısıl işleminin, kaolinin puzolanik aktivitesi üzerindeki etkisi incelenmiştir. Bu kapsamda ev tipi mikrodalga fırın kullanılarak 10 dakika boyunca 300, 450, 600 ve 800 watt güç seviyesinde ısıl işleme maruz bırakılan kaolinlerin dayanım aktivite indeksi belirlenmiştir. Sonuçlar yüksek sıcaklık fırınında 600, 700 ve 800°C’de 1, 3 ve 5 saat kalsine edilen kaolinler ile kıyaslanmıştır. Sonuçta, yüksek sıcaklık fırınında kalsine edilen kaolinin 28 günlük dayanım aktivite indeksinin %82.5-107.9 aralığında olduğu, mikrodalga ısıl işlemi uygulanan kaolinde ise bu değerin %74.3-80.5 arasında değiştiği tespit edilmiştir. Mikrodalga ısıl işlemine tabi tutulmuş kaolinlerin dayanım aktivite indekslerinin, ham kaoline oranla %4.6-13.3 oranında daha yüksek olması, mikrodalga ısıl işleminin kalsinasyon için potansiyel taşıdığını göstermiştir.

Anahtar Kelimeler

• Kaolin
• Metakaolin
• Kalsinasyon
• Mikrodalga
• Basınç dayanımı

Kaynakça

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