Karma Lifli Betonların Tek Eksenli Çekme Altında Çatlak Yapısının İncelenmesi

Yıl 2020, Cilt: 31 Sayı: 1, 9773 - 9787, 01.01.2020

Burcu Akçay Aldanmaz

https://doi.org/10.18400/tekderg.419819

Cited By: 3

Öz

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.

Anahtar Kelimeler

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

Crack Pattern Investigation of Hybrid Fibre Reinforced Concrete under Uniaxial Tension

Öz

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. 

Anahtar Kelimeler

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

Kaynakça

• [1] Rossi, P., Acker, P., Mallier, Y., Effect of steel fibres at two stages: the material and the structure. Mater. Struct., 20, 436-439, 1987.
• [2] Mobasher, B., Li, C.Y., Mechanical properties of hybrid cement-based composites. ACI Mater. J., 93(3), 284-292, 1996.
• [3] Yao, W., Li, J., Wu, K., Mechanical properties of hybrid fiber-reinforced concrete at low fiber volume fraction. Cem. Conc. Res., 33(1), 27-30, 2003.
• [4] Lawler, J.S., Wilhelm, T., Zampini, D., Shah, S.P., Fracture processes of hybrid fiber-reinforced mortar. Mater. Struct., 36(257), 197-208, 2003.
• [5] Banthia, N., Gupta, R., Hybrid fiber reinforced concrete (HyFRC): fiber synergy in high strength matrices. Mater. Struct., 37(274), 707-716, 2004.
• [6] Banthia, N., Sappakittipakorn, M., Toughness enhancement in steel fiber reinforced concrete through fiber hybridization. Cem. Conc. Res., 37(9), 1366-1372, 2007.
• [7] Sahmaran, M., Yaman, I.O., Hybrid fiber reinforced self-compacting concrete with a high-volume coarse fly ash. Cons. Build. Mater., 21(1), 150-156, 2007.
• [8] Kim, D.J., Park, S.H., Ryu, G.S., Koh, K.T., Comparative flexural behavior of Hybrid Ultra High Performance Fiber Reinforced Concrete with different macro fibers. Cons. Build. Mater., 25(11), 4144-4155, 2011.
• [9] Kim, D.J., Park, S.H., Ryu, G.S., Koh, K.T., Tensile behavior of Ultra High Performance Hybrid Fiber Reinforced Concrete. Cem. Conc. Compos., 34(2), 172-184, 2012.
• [10] Akcay, B., Tasdemir, M.A., Mechanical behaviour and fibre dispersion of hybrid steel fibre reinforced self-compacting concrete. Cons. Build. Mater., 28(1), 287-293, 2012.
• [11] Markovic, I., van Mier, J.G.M., Walraven, J.C., Development of high performance hybrid fibre concrete, Proceedings 4th International RILEM Workshop on High Performance Hybrid Fibre Concrete HPFRCC-4 (Naaman, A.E., Reinhardt, H.W., Eds.), RILEM Publications S.A.R.L., Bagneuax, France, Mainz, Germany, 277-300. 2003.
• [12] van Mier, J.G.M., Reality behind the fictitous crack?, Proceedings of International Conference on Fracture of Concrete and Concrete Structures-FraMCos 5, Evanston, Illinois, 11-30, 2004.
• [13] van Mier, J.G.M., Framework for a generalized four-stage fracture model of cement-based materials. Eng. Fract. Mech., 75(118), 5072–86, 2008.
• [14] van Vliet, M.R.A., Size effect in tensile fracture of concrete and rock, PhD Thesis, Delft University of Technology, The Netherlands, 2000.
• [15] Ferro, G., Effetti di scala sulla resisrenza a trazione dei materialli (Scale effects on tensile properties of materials), PhD thesis, Politecnico di Torino, 1994.
• [16] van Mier, J.G.M., Mode I fracture of concrete: discontinuous crack growth and crack interface grain bridging. Cem. Concr. Res., 21(1), 1-15, 1991.
• [17] van Mier, J.G.M., Vervuurt, A., Schlangen, E., Boundary and size effects in uniaxial tensile tests: a numerical and experimental study, Proceedings of International Conference on Fracture and Damage of Quasi-Brittle Structures (Bazant, Z.P., Bittnar, Z., Jirasec, M., Mazars, J., Eds), E&FN Spon, London/NewYork, I 289–302, 1994.
• [18] van Mier, J. G.M., Mechtcherine, V., Minimum demands for deformation-controlled uniaxial tensile tests, RILEM TC 187-SOC, Experimental Determination of the Stress-Crack Opening Curve for Concrete in Tension (Planas, J. Ed.), Report 39, RILEM Publications S.A.R.L., Bagneux, France, 5-12, 2007.
• [19] Gjorv, O.E., Sorenson, S., Arnesen, A., Notch sensitive and fracture toughness of concrete. Cem. Conc. Res., 7, 333-344, 1977.
• [20] van Mier, J.G.M, Schlangen, E., Vervuur,t A., Tensile cracking in concrete and sandstone. Part II-effect of boundary conditions. Mater. Struct., 29(186), 87-96, 1996.
• [21] Mechtcherine, V., Testing behaviour of strain hardening cement-based composites in tension - summary of recent research, Proceedings 5th international conference on High Performance Fiber Reinforced Cement Composites HPFRCC-5 (Reinhardt, H.W., Naaman, A.E., Eds.), RILEM Publications S.A.R.L., Bagneuax, France, Mainz, Germany, 3-12, 2007.
• [22] Naaman, A. E., Fischer, G., Krstulovic-Opara, N., Measurement of tensile properties of fibre reinforced concrete: Draft submitted to ACI Committee 544. Proceedings 5th international conference on High Performance Fiber Reinforced Cement Composites HPFRCC-5 (Reinhardt, H.W., Naaman, A.E., Eds.), RILEM Publications S.A.R.L., Bagneuax, France, Mainz, Germany, 3-12, 2007.
• [23] Akcay, B., Experimental investigation on uniaxial tensile strength of hybrid fibre concrete. Compos. Part B- Eng., 43(2), 766-778, 2012.
• [24] Markovic, I., High Performance Hybrid Fibre Concrete-Development and Utilisation, PhD Thesis, Delft University of Technology, The Netherlands, 2006.
• [25] Carpinteri, A., Ferro, G., Size effects on tensile fracture properties: a united explanation based on disorder and fractality of concrete microstructure. Mater. Struct., 10(2), 563-571, 1994.
• [26] Schlangen, E., Experimental ad numerical analysis of fracture process in concrete, PhD Thesis, Delft University of Technology, The Netherlands, 1993.
• [27] Stähli, P., van Mier, J. G. M., Manufacturing, fibre anisotropy and fracture of hybrid fibre concrete. Eng. Fract. Mech., 74, 223-242, 2007.
• [28] Vořechovský, M., Interplay of size effects in concrete specimens under tension studied via computational stochastic fracture mechanics. Int. J. of Solids and Struct., 44(9), 2715-2731, 2007.