Karma Lifli Betonların Tek Eksenli Çekme Altında Çatlak Yapısının İncelenmesi

Abstract

Karma lifli betonların kırılmasında lif hacmi ve lif boyutunun etkisi tek eksenli çekme deneyi ile belirlenmiştir. Kemik şeklindeki numuneler serbest dönen mafsallı yükleme düzeneğinde tek eksenli çekme altında yüklenmiştir. Deney sonuçları lif hacmi arttıkça hem çekme dayanımının hem de yük-deplasman grafiğinin altında kalan alanın yani betonun tokluğunun arttığını göstermiştir. Kısa liflerin yalnızca tepe yükünü arttırmadığı uzun lifler ile birlikte karma olarak kullanıldığında tepe yükünden sonraki davranışa da etkiyerek tokluğu da arttırdığı görülmüştür. Görüntü analizleri karma lifli betonlarda çatlağın hiçbir zaman doğrusal olmadığını, betonun iç kısımlarına ilerledikçe dış yüzeyde görünmeyen çoklu çatlamanın, dallanma ve köprülenmenin bulunduğunu göstermiştir. Kısa lifler arttıkça ortalama çatlak alanı belirgin bir şekilde artarken uzun liflerin miktarı arttıkça en büyük çatlak açıklığının arttığı belirlenmiştir.

Keywords

• Çatlak yapısı,dijital görüntü analizi,karma lifli beton,lif geometrisi,lif hacmi

Crack Pattern Investigation of Hybrid Fibre Reinforced Concrete under Uniaxial Tension

Abstract

The effect of size and volume of fibres on the fracture of hybrid fibre reinforced concrete was determined by applying uniaxial tensile test. The bone shaped specimens were loaded under uniaxial tension by using freely rotated support loading test setup. The test results showed that the increase in fibre volume results in an increase in both tensile strength and the area under the load displacement curve, which is the measure of the material toughness. It was shown that the use of short fibres not only increased the peak load but also affected the post-peak behaviour and increased the toughness especially when they were used together with long fibres. The image analyses pointed out that in hybrid fibre reinforced concrete the crack patterns are not in general linear. Instead, the cracks propagate inside the samples forming multiple cracks and crack branches as well as developing bridging, though these features are not observed on the surface of the samples. The results showed that with increasing amount of short fibres the average crack area was increased, while the use of long fibres in more abundance increased the width of the largest crack. 

Keywords

• Crack pattern,digital image analysis,hybrid fibre reinforced concrete,fibre geometry,fibre volume,uniaxial tensile test

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