Mineral katký kullanýmýnýn hava sürükleyici katkýlý çimentolu harçlarýn taze ve sertleþmiþ hal özeliklerine etkisi

Bu çalýþmada, silis dumaný ve uçucu kül kullanýmýnýn hava sürükleyici katkýlý tekli, ikili ve üçlü çimentolu sistemleri içeren harç karýþýmlarýnýn taze ve bazý sertleþmiþ hal özelliklerine etkisi karþýlaþtýrmalý olarak incelenmiþtir. Bu kapsamda tek tip CEM I 42.5R tipi çimento, tek tip polikarboksilat esaslý su azaltýcý katký, tek tip hava sürükleyici katký, silis dumaný ve uçucu kül kullanarak farklý kombinasyonlara sahip harç karýþýmlarý hazýrlanmýþtýr. Mineral katký içermeyen kontrol karýþýmýna ilaveten, üç seri daha harç karýþýmý hazýrlanmýþtýr. Birinci ve ikinci seride uçucu kül ve silis dumaný sýrasýyla, %30 ve %10'u oranýnda çimento ile yer deðiþtirmiþtir. Üçüncü seride ise, çimento aðýrlýðýnýn %30 ve %10 oranýnda, hem uçucu kül hem de silis dumaný kullanýlmýþtýr. Çalýþmada tüm harç karýþýmlarýnda su/çimento oraný, kum/baðlayýcý oraný ve yayýlma deðerleri sýrasýyla, 0.485, 2.75, 270±20 mm olarak sabit tutulmuþtur. Harç karýþýmlarýnýn zamana baðlý yayýlma deðerleri, 90 günlük su emme deðerleri, 3, 7, 28 ve 90 günlük basýnç dayanýmlarý ve 0, 50, 100, 150, 200 donma-çözülme çevrimi sonrasý basýnç dayaným deðerleri elde edilmiþtir. Deney sonuçlarýna göre, hava sürükleyici katkýlý çimento harçlarýnda mineral katký kullanýmý karýþýmlarýn taze hal özelliklerini olumlu yönde etkilemiþtir. Mineral katký içeren karýþýmlar erken yaþlarda kontrol karýþýmýna kýyasla daha düþük dayaným gösterirken, 90 günün sonunda kontrol karýþýmýndan daha yüksek basýnç dayaným deðerlerine sahip olmuþlardýr. Mineral katký kullanýmý ile harç karýþýmlarýnýn 90 günlük su emme deðerleri, kontrol karýþýmýna kýyasla daha düþük olmuþtur. Donma-çözülme çevrimleri bakýmýndan en baþarýlý karýþýmýn hem uçucu kül hem de silis dumaný içeren, üçlü baðlayýcý sisteme sahip olan K-UK-SD-HSK karýþýmý olduðu tespit edilmiþtir.

Effect of utilization of mineral admixture on the fresh and hardened properties of air-entrained cement mortars

In this study, the effect of silica fume and fly ash on the fresh and some hardened state properties of mortar mixtures containing plain, binary and ternary cementitious systems and air entraining admixture were investigated comparatively. Within this regard, different mortar admixture combinations were prepared by using a CEM I 42.5R type cement, a type of polycarboxylate-ether based water reducing admixture, air entraining admixture, silica fume and fly ash. In addition to the control mixture containing no mineral admixture, three series of mortar mixtures were prepared. In the first and second series, silica fume and fly ash were replaced by 30% and 10% of cement, respectively. In the third series, both silica fume and fly ash were used as 30% and 10% of cement weight. Within all mortar mixtures, water/cement ratio, sand/binder ratio and flow values were kept constant as 0.485, 2.75, 270±20 mm, respectively. Time-dependent flow values, 90-day water absorption values, 3, 7, 28 and 90-day compressive strengths and compressive strengths values after 0, 50, 100, 150, 200 freeze-thaw cycle of mortar mixtures were measured. According to the results, the use of mineral additives in cement mortars containing air-entraining admixture had a positively effect on the fresh state properties of the mixtures. While mixtures containing mineral admixture exhibited lower strengths at early ages compared to the control mixture, they had higher compressive strength values than the control mixture at the end of 90 days. The 90-day water absorption values of the mortar mixtures were observed to be less with the use of mineral admixture compared to that of control mixtures. In terms of freeze-thaw cycles, the most successful mixture was determined to be K-UK-SD-HSK mixture having ternary cementitious system and containing both fly ash and silica fume.