Investigation of Sulphate Resistance of Concretes Containing Silica Fume Exposed to Sodium Sulphate at Different Concentrations

Öz

In this study, the properties of concretes containing silica fume (SF) at different substitution levels after exposure to sodium sulfate solution were investigated. For this purpose, 5%, 10% and 15% SF were used according to the cement weight. The mixtures were kept in Na2SO4 solution with 3%, 5% and 10% concentrations for 30, 60, 90 and 120 day periods. Compressive strength losses and expansion ratios of all mixtures after exposure to solution were determined. In addition, the slump values of the mixtures as fresh concrete properties were also measured. A superplasticizer was used especially in order not to decrease the slump values of SF added mixtures. Thus, there was no significant decrease in the slump values of the SF-added mixtures. The test results showed that the presence of SF had a positive effect on the strength loss caused by the sodium sulfate effect. The best resistance to sodium sulfate attack was obtained with 15% SF substitution; A strength loss of 3% to 8% was detected in a 120-day period and at all concentrations. In particular, the strength of the samples exposed to 3% concentrated solution increased at early ages (30 and 60 days). This can be attributed to the filling of the pore spaces by the expanding products and the thickening of the mortar matrix. While the relative residual compressive strength of the control sample kept in 10% concentration solution ranged between 94% and 77.95%, these values were obtained between 100.31% and 92.35% for the SD-15 sample. In addition, it was observed that the expansion values of the samples exposed to the Na2SO4 solution were similar to the compressive strength results.

Anahtar Kelimeler

• Na2SO4
• Sulfate resistance
• Silica füme
• Concentration
• Expansion value

Farklı Konsantrasyonlarda Sodyum Sülfata Maruz Kalan Silis Dumanı İçerikli Betonların Sülfat Direncinin İncelenmesi

Öz

Bu çalışmada, farklı ikame seviyelerinde silis dumanı (SD) içeren betonların sodyum sülfat çözeltisine maruz kaldıktan sonraki özellikleri incelenmiştir. Bu amaçla, çimento ağırlığına göre %5, %10 ve %15 oranında SD kullanılmıştır. Karışımlar %3, %5 ve %10 konsantrasyona sahip Na2SO4 çözeltisinde 30, 60, 90 ve 120 günlük periyodlarda bekletilmiştir. Tüm karışımların çözeltiye maruz kalma sonrası basınç dayanım kayıpları ve genleşme oranları tespit edilmiştir. Ayrıca karışımların taze beton özelliği olarak çökme değerleri ölçülmüştür. Özellikle SD ilaveli karışımların çökme değerlerinin azalmaması için süper akışkanlaştırıcı kullanılmıştır. Böylelikle SD ilaveli karışımların çökme değerlerinde kayda değer düşüşler meydana gelmemiştir. Test sonuçları, SD varlığının, sodyum sülfat etkisinden kaynaklanan dayanım kaybı üzerinde olumlu bir etkiye sahip olduğunu göstermiştir. Sodyum sülfat saldırısına karşı en iyi direnç, %15'lik SD ikamesi ile elde edilmiş olup; 120 günlük periyodda ve tüm konsantrasyon oranlarında %3 ile %8 arasında dayanım kaybı tespit edilmiştir. Özellikle %3 konsantrasyonlu çözeltiye maruz bırakılan numunelerin erken yaşlarda (30 ve 60.gün) dayanımlarında artış meydana gelmiştir. Bu durum, gözenek boşluklarının genişleyen ürünler tarafından doldurulmasına ve harç matrisinin yoğunlaştırılmasına bağlanabilir. %10 konsantrasyona sahip çözeltide bekletilen kontrol numunesinin bağıl artık basınç dayanımı %94 ile %77.95 aralığında değişirken, SD-15 numunesi için bu değerler %100.31 ile %92.35 aralığında elde edilmiştir. Ayrıca Na2SO4 çözeltisine maruz kalan numunelerin genleşme oranları, basınç dayanımı sonuçları ile benzerlik gösterdiği gözlemlenmiştir.

Anahtar Kelimeler

• Na2SO4
• Sülfat direnci
• Silis dumanı
• Konsantrasyon
• Genleşme oranı

Kaynakça

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