Büzülme engelleyici katkıların harç karışımlarının basınç dayanımına, su emmesine ve kuruma-büzülmesine etkisi

Bu çalışmada, kuruma büzülme engelleyici (KBE) katkı içeren harç karışımlarının basınç dayanımı, su emme oranı ve kuruma büzülmesi incelenmiştir. Bu amaçla,4 farklı fabrika ürünü 9 adet toz ve sıvı halinde katkı kullanılmıştır. Tüm harç karışımlarında bağlayıcı olarak CEMI 42.5 R tipi çimento ve agrega olarak standart kum kullanılmıştır. KBE katkı içermeyen kontrol karışımına ilaveten çimento ağırlığının %2'si kadar KBE katkı kullanılarak toplamda 10 seri karışım hazırlanmıştır. Üretilen tüm harç karışımlarında, kum/bağlayıcı oranı, su/çimento (S/Ç) oranı ve yayılma değeri sırasıyla, 2.75, 0.485 ve 230±20 mm olarak sabit tutulmuştur. Hedeflenen yayılma değerlerini sağlamak için tek tip polikarboksilat-eter esaslı yüksek oranda su azaltıcı katkı kullanılmıştır. Hazırlanan harç karışımlarının 1, 3, 7 ve 28 günlük basınç dayanımları ve 28 günlük su emme oranı elde edilmiştir. Ayrıca söz konusu karışımların 28 günlük kuruma büzülme davranışı incelenmiştir. Deney sonuçlarına göre, kontrol karışımına kıyasla, KBE katkı kullanımı ile harç karışımlarının basınç dayanımı ve geçirgenlik özellikleri genel olarak olumlu etkilenmiştir. Ancak, 2 farklı KBE katkı kullanımı harç karışımlarının priz almamasına sebep olmuştur. Söz konusu karışımlarda su azaltıcı katkı kullanılmamıştır. Ayrıca, KBE katkı kullanımı ile harç karışımlarının kuruma büzülme değerlerinde %10- %45 oranında azalmalar tespit edilmiştir. Sıvı halinde olan KBE katkılar genel olarak toz halinde olan katkılara kıyasla kuruma-büzülme davranışı açısından daha başarılı olmuştur.

Effect of shrinkage reducing admixture on compressive strength, water absorption and drying-shrinkage of mortar mixture in the presence of water reducing admixture

In this study, compressive strength, water absorption and drying-shrinkage behaviour of shrinkage-reducing admixture (SRA) bearing mortar mixture were investigated. For this purpose, 9 powder and liquid commercial SRA admixtures provided from 4 different factories were used. In all mortar mixture, CEM I 42.5 R type cement as binder and standard sand as aggregate were used. In addition to the containing no SRA admixture, 10 different mortar mixtures were produced by using SRA admixture as 2 wt.% of the cement. In all mortar mixtures, water/cement ratio, sand/binder ratio and flow value were kept constant as 0.485, 2.75 and 230 ± 20 mm, respectively. A type of polycarboxylate-ether based high range water reducing admixture was used for providing the desired flow values. 1, 3, 7 and 28-day compressive strength and 28-day water absorption of mortar mixtures were obtained. Also, the 28-day drying-shrinkage of mortar mixtures was measured. Test results demonstrated that utilization of SRA positively affected compressive strength and permeability of the mortar mixtures. However, utilization of SRA led to incompletion of setting time of mortar mixtures. In the mentioned mortar mixtures, water reducing admixture was not used. In addition, a reduction of %10- %45 was found in drying shrinkage value of mortar mixtures by utilization of SRA. The liquid types of SRA generally were more successful compared to the powder types in term of drying-shrinkage behaviour of mortar mixtures.

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