13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Mechanical Characterization of Sisal Fiber Reinforced Cement Mortar Roberto Fujiyama1, Fathi Darwish2, Marcos Pereira3,* 1 Department of Mechanical Engineering, Pará Federal University, Belém PA 66075-110, Brazil 2 Department of Civil Engineering, Fluminense Federal University, Niterói RJ 24210-240, Brazil 2 Department of Materials Engineering, Catholic University of Rio de Janeiro, Rio de Janeiro RJ 22451-901, Brazil * Corresponding author: marcospe@puc-rio.br Abstract The purpose of this work is to evaluate the mechanical characteristics of sisal fiber reinforced cement mortar. The composite material was produced from a mixture of sand, cement and water in the proportions of 1:1:0.4, respectively. Sisal fibers, amounting to 3% of the weight of cement, were added to the mixture in two different lengths, namely 25 and 45 mm. Mechanical characterization of both the composite and the plain mortar was carried out by means of three point bend, compression and impact tests. Specimens containing parallel sided notches of different root radii were loaded in three point bending in an effort to determine the effect of the fibers on the fracture behavior of the material in the presence of discontinuities. The results obtained indicate that, while fiber reinforcement leads to a decrease in the ultimate compressive strength, J integral calculations at maximum load for the different notch root radii have indicated, particularly for the case of long fibers, a significant superiority of the reinforced material in comparison with the plain cement mortar, in consistence with the impact test data. Keywords Composite material, Impact energy, Fracture initiation, J-integral 1. Introduction It is well known that the presence of short randomly dispersed fibers in a cementitious matrix can result in an appreciable improvement in the mechanical behavior of the produced composite. This improvement is clearly manifested by the significant superiority of the composite´s toughness in comparison with that of the plain matrix. The increase in toughness, due to the incorporation of fibers, can be attributed, largely, to the fiber bridging mechanism, whereby the fibers take an active part in supporting tensile loading, in controlling matrix microcracking and in reducing the rate of crack propagation. The fiber reinforced concrete will, therefore, exhibit a pseudoductile behavior, maintaining considerable load carrying capacity after cracking of the matrix. Starting early seventies, a number of studies [1-4] have been made regarding the use of natural fibers, such as sisal and bamboo, as reinforcing elements in cement mortars and in concretes. The focus in these works has been on the evaluation of the mechanical properties of the resulting composites as a function of the characteristics of their constituents, and the results obtained have indicated the viability of using natural fibers as reinforcing agents in cementitious matrices. The present work was initiated with the purpose of evaluating the effect of sisal fibers on the compressive strength and fracture resistance of hardened cement mortar. Taking into account their potential use in structural applications, the evaluation of the notch sensitivity of sisal fiber reinforced mortar, in comparison with that of plain mortars, is considered to be an important undertaking. Accordingly, the J-integral approach was adopted and specimens containing deep notches of different root radii were cast in appropriate molds, cured and then loaded in three point bending. The J-integral values at maximum load were calculated and correlated with the notch root
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