Polikarboksilat-bazlı süperakışkanlaştırıcıların silis dumanı içeren çimento hamurlarının reolojik davranışına etkileri

İnşaat sektöründe üstün özelliklere sahip çimento-esaslı yapı malzemelerine olan ihtiyaç gün geçtikçe artmaktadır. Bu çalışmada, beton karışımlara yüksek oranda akışkanlık sağlayan yeni nesil polikarboksilat-bazlı süperakışkanlaştırıcıların farklı türevleri sentezlenmiş, karakterize edilmiş ve silis dumanı içeren çimento hamurlarında performansları test edilmiştir. Farklı moleküler yapılara sahip bu polimerlerin çimento hamurlarının akışkanlık özelliklerine etkileri mini-çökme ve reoloji deneyleri ile araştırılmıştır. Reolojik davranışların incelenmesinde Bingham ve Herschel-Bulkley olmak üzere iki farklı model yaklaşımı kullanılmıştır. Süperakışkanlaştırıcı yapısında fumarik asit gibi bir dikarboksilik asit bulunmasının hamurların işlenebilirliğinde ve bu işlenebilirliğin zamana bağlı korunumunda etkileri olduğu gözlenmiştir. Sentezlenen süperakışkanlaştırıcıların hamur yayılma çapını katkısız hamura göre %100’ün çok üzerinde arttırdığı ve karışımların zamana bağlı (2 sa.) etkin akışkanlık davranışı için tercih edilebileceği belirlenmiştir. Ayrıca bağlayıcı olarak sadece çimento içeren harçlarla karşılaştırıldığında, söz konusu süperakışkanlaştırıcıların çimento ve silis dumanlı harçlarda mekanik dayanımları geliştirdiği görülmüştür. Sonuç olarak, sentezlenen yeni nesil polikarboksilatların yüksek performanslı beton üretimlerinde kullanılma potansiyelinin bulunduğu anlaşılmıştır.

Anahtar Kelimeler:

Polikarboksilat, Silis dumanı, Çimento, Reoloji, Dayanım

The effects of polycarboxylate-based superplasticizers on the rheological behaviours of cement pastes containing silica fume

In construction sector, the necessity to cement-based materials having superior properties is increasing day by day. In this study, novel forms of new generation polycarboxylate-based superplasticizers which provide higher fluidity to concrete mixtures were synthesized, characterized and their performances in cement pastes containing silica fume were tested. The influences of polymers possessing different molecular structures on the flow properties of cement pastes were investigated with mini-slump and rheology tests. Two different model approaches as Bingham and Herschel-Bulkley were used to examine rheological behaviours. It was observed that, the existence of dicarboxylic acid as fumaric acid in superplasticizer structure have effects on pastes’ workability and the time-dependent retention of this workability. It was determined that, synthesized superplasticizers increase the flow diameter of paste over 100% than plain paste and can be preferable for the effective fluidity behaviours of mixtures by time (2 hours). Additionally comparing with mortars containing only cement as binder, it was seen that superplasticizers in question improve the mechanical strengths of mortars possessing cement and silica fume. As a result, it was understood that the synthesized new generation polycarboxylates have potential to be used in high performance concrete production.

Keywords:

Polycarboxylate, Silica fume, Cement, Rheology, Strength,

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