Çok Yüksek Hacimde Uçucu Kül İçeren Sentetik ve 5D Çelik Lif Donatılı Çimento Esaslı Kompozitlerin Mühendislik Özellikleri

Çimento esaslı harçlarda yüksek hacimlerde kullanılan uçucu küller ekonomik bir tasarımın yanında çeşitli taze ve sertleşmiş özellikleri modifiye etmektedir. Kullanılacak uçucu kül tipine göre değişmekle birlikte, istenen mühendislik özelliklerine göre seçilecek bir karışım tasarımı yüksek oranda uçucu külün kullanımını mümkün kılarak, çimento esaslı harçların içerisinde matris ile lif arasındaki ilişkiyi değiştirebilir. Bu çalışmada, toplam bağlayıcı ağırlığınca çok yüksek oranda (%80) uçucu kül içeren çimento esaslı kompozitler polyamid lif (PL) ve beş boyutlu çelik liflerle (5D-ÇL) tekli ve hibrit formda geliştirilerek mühendislik özellikleri açısından araştırılmıştır. Bunun yanında, lif donatılı kompozitlerin basınç mukavemetleri 7, 28, 60 ve 90 günlük kür yaşlarında belirlenmiştir. Tekli ve hibrit formda farklı tür lif donatılı çimento esaslı kompozitlerin mühendislik özellikleri, akma ve kırılma noktalarındaki yük ve deplasman değerleri, maksimum taşıma kapasitesi, süneklik oranı, rijitlik ve enerji yutma kapasitesi parametreleri dikkate alınarak değerlendirilmiştir. Sonuçlar bir arada kullanılan PL ve 5D-ÇL liflerinin tek formda kullanılmalarına göre matris-lif bağ davranışı açısından sinerji meydana getirdiğini ve buna bağlı olarak süneklik, başlangıç rijitlik ve enerji yutma kapasitelerini arttırdığını işaret etmektedir. Ayrıca tekil olarak lifler irdelendiğinde, 5D-ÇL’lerin PL liflerine göre mühendislik özelliklerini iyileştirmede daha etkili olduğu düşünülmektedir. Uçucu kül/çimento oranı ağırlıkça 4,0 olan kompozitlerin, erken yaş mekanik özelliklerin belirleyici olmadığı inşaat mühendisliği uygulamalarında ekonomiklik ve yapısal performans açısından sürdürülebilir bir tasarım olduğu düşünülmektedir.

Anahtar Kelimeler:

“Uçucu kül, sentetik lifler, beş boyutlu çelik lifler, çimento esaslı harçlar, mühendislik özellikleri”

Engineering Properties of Very High Volume Fly-ash Cementitious Composites Reinforced with Synthetic and 5D Steel Fibers

In cement-based mortars, using high volume of fly ash modifies several fresh and hardened properties besides an economical design. Although it varies according to the type of fly ash to be used, mixture design proving high amount of fly ash which is pre-targeted according to engineering properties may modify the relationship between matrix and fibers in the cement-based mortars. In this study, cement-based composites containing a very high percentage of fly ash (80%) by total binder weight were developed with polyamide fiber (PL) and five-dimensional steel fibers (5D-ÇL) in single and hybrid forms and investigated in terms of engineering properties. In addition, compressive strength of fiber reinforced composites were assessed at the curing ages of 7, 28, 60 and 90 days. The engineering properties of cementitious composites reinforced with single and binary use of different fibers were obtained by considering load and displacement values at yield and fracture points, maximum load-carrying capacities, ductility, rigidity and energy dissipation capacity. Results reveal that binary use of PL and 5D-ÇL provided a synergy in terms of matrix-fiber bond behavior compared to their single use thus increasing the ductility, initial rigidity and energy dissipation capacities. In addition, in the case of examining single use of fibers, it was found that 5D-ÇL was more effective than PL fibers for improving the engineering properties. It is considered that composites having fly ash/cement ratio of 4.0 by weight are sustainable in terms of economically and performance in the civil engineering applications where early-age mechanical properties is not significative.

Keywords:

“Fly ash, synthetic fibers, five dimensional steel fibers, cementitious composites, engineering properties”,

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