Evaluation of Waste Tea Ash as A Silica Source in Cementless Geopolymer Composites

Abstract

This study investigates the evaluation of waste tea ash (ACK) as a sustainable silica source in metakaolin-based geopolymer composites. To isolate the specific effect of WTA on the geopolymer system, silica fume was replaced with different proportions of ACK while maintaining a constant Si/Al molar ratio (3). The effects of WTC on mechanical behaviour, physical properties, and microstructural evolution were comprehensively investigated through compressive and flexural strength tests, ultrasonic pulse velocity (UPV), water absorption, density measurements, and XRD and FT-IR analyses. The results showed a contradictory mechanical trend: while compressive strength decreased at high ACK content (up to 30.3%), flexural strength improved significantly (up to 38.8% increase). This was attributed to the microfibrous ACK particles acting as crack bridging agents. Despite the observed densification and reduced porosity, 28-day UAH values decreased due to the formation of finer but more discontinuous pores as a result of microstructural refinement. The findings emphasise the dual role of AÇK as both a reactive precursor and a microstructural regulator, demonstrating its potential for developing bend-dominant, environmentally friendly geopolymer materials suitable for non-load-bearing or fire-resistant applications.

Keywords

• Tea waste ash
• Metakaolin geopolymer
• Mechanical behaviour
• Microstructural evolution
• Sustainable construction materials
• Agricultural waste utilisation

Atık Çay Külünün Çimentosuz Geopolimer Karışımlarda Silika Kaynağı Olarak Değerlendirilmesi

Abstract

Bu çalışma, atık çay külünün (AÇK) metakaolin esaslı geopolimer kompozitlerde sürdürülebilir bir silika kaynağı olarak değerlendirilmesini araştırmaktadır. AÇK'nın geopolimer sistemi üzerindeki spesifik etkisini izole etmek amacıyla, sabit Si/Al molar oranı (3) korunarak silika dumanının yerine farklı oranlarda AÇK ikame edilmiştir. AÇK'nın mekanik davranış, fiziksel özellikler ve mikroyapısal evrim üzerindeki etkileri, basınç ve eğilme dayanımı deneyleri, ultrasonik atım hızı (UAH), su emme, yoğunluk ölçümleri ile XRD, FT-IR analizleri aracılığıyla kapsamlı olarak incelenmiştir. Sonuçlar, zıt yönlü bir mekanik eğilim göstermiştir: yüksek AÇK içeriğinde basınç dayanımı azalırken (%30,3'e kadar), eğilme dayanımı önemli ölçüde iyileşmiştir (%38,8'e kadar artış). Bu durum, mikro-lifli AÇK parçacıklarının çatlak köprüleme ajanları olarak görev yapmasına atfedilmiştir. Gözlemlenen yoğunlaşma ve azalan gözenekliliğe rağmen, mikroyapısal arıtma sonucu daha ince ancak daha kopuk gözenekler oluşması nedeniyle 28 günlük UAH değerleri düşmüştür. Bulgular, AÇK'nın hem reaktif öncül hem de mikroyapısal düzenleyici olarak ikili rolünü vurgulamakta ve yük taşımayan veya yangına dayanıklı uygulamalar için uygun, eğilme baskın, çevre dostu geopolimer malzemeler geliştirilmesindeki potansiyelini göstermektedir.

Keywords

• Atık çay külü
• Metakaolin geopolimer
• Mekanik davranış
• Mikroyapısal evrim
• Sürdürülebilir inşaat malzemeleri
• Tarımsal atık değerlendirme

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