13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Wedge Splitting Test on Fracture Behaviour of Fiber Reinforced and Regular High Performance Concretes Kamil Hodicky,*1, Thomas Hulin1, Jacob W. Schmidt1 and Henrik Stang1 1Department of Civil Engineering, Technical University of Denmark, Kongens Lyngby, DK-2800, Denmark * Corresponding author: kamh@byg.dtu.dk Abstract The fracture behaviour of three fiber reinforced and regular High Performance Concretes (HPC) is presented in this paper. Two mixes are based on optimization of HPC whereas the third mix was a commercial mix developed by CONTEC ApS (Denmark). The wedge splitting test setup with 48 cubical specimens was used experimentally and the cracked non-linear hinge model based on the fictitious crack model was applied for the interpretation of the results. The stress-crack opening relationships were extracted by using inverse analysis algorithm for various multi-linear softening curves. The fracture mechanics parameters such as crack opening displacement (COD), fracture energy and characteristic length were experimentally determined. Experiments were performed at 1, 3, 7 and 28 days. Fracture energy, Gf, was found to increasing with age, while the characteristic length, Lch, was found to decrease. Keywords High Performance Concrete, Wedge Splitting Test, Inverse Analysis, Fictitious crack model. 1. Introduction Development of fiber reinforced concrete plays important role in industrialization of the building industry. The possibility of replacement of ordinary reinforcement is presently very important topic [1]. The number of practical applications of fiber-reinforced High Performance Concrete (HPC) is increasing like foundation slabs, foundations and walls. The fibres are likely to replace the ordinary reinforcement completely [2]. While the other structures like beams and slab, fibers can be used in combination with ordinary reinforcement or pre-stressed reinforcement. The both cases show improvement of working environment at the construction site and potential benefits due to economical factors. The one of main benefits of fiber reinforcement is an ability to transfer stress across a crack. However, if fiber-reinforced HPC is to be a more widely used material, general simple test method is needed for the concrete industry. This is necessary for fiber-reinforced HPC, where industry lacks such a method to verify their daily production quality control. Further, it would provide relevant material data allowing to the structural engineers design of structures that are safe and cost-efficient. As design tools seem to become more advanced and the design requirements are more complex, the need of fracture properties is required for structural analysis. Therefore there is a need of simple test method that allows determining the fracture properties of fiber-reinforced HPC with acceptable accuracy, which can be used by companies in their daily production without expensive investment to testing equipment. In last two decades the tensile behaviour of non-fiber and fiber reinforced concretes is mostly described by the concepts of the fictitious crack model. The most often used non-linear fictitious crack model was originally developed by Hillerborg [3]. This model is able to closely describe the fracture properties of concrete. However, determination of softening curves of stress-crack opening relationships can cause particular difficulties like in case of uniaxial tensile test and three point bending [4]. Another option is the wedge splitting test setup (WST), which is made for indirect determination of the softening curve. The WST was originally proposed by Linsbauer and Tschegg [5] and later developed by Brühwiler and Wittmann [6]. The researchers have greatly used the WST-method, and recently interest in the method increased rapidly. Its main advantage lies in its simplicity and stability. Furthermore, a standard cube is used, but the test can also be performed on core-drilled samples from the existing structure. Moreover, it was proven by Østergaard et al. [4] and Hansen et al. [7] that the test is suitable for early-aged concretes because it doesn’t suffer
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