TOUGHNESS FACTOR OF POLYPROPYLENE FIBER REINFORCED CONCRETE IN AGGRESSIVE ENVIRONMENT

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1 PAPER REF: 2811 TOUGHNESS FACTOR OF POLYPROPYLENE FIBER REINFORCED CONCRETE IN AGGRESSIVE ENVIRONMENT Raimundo E. Vasconcelos 1(*), Syme S. Queiroz 2, Itamar Ferreira 3, Marco A. Carnio 4, André Y. Uehara 5 1,2 Department of Civil Building, Federal Institute of Pará (IFPA), Belém City, Pará State, Brazil. 1,2,3 School of Mechanical Eng., University of Campinas (Unicamp), Campinas City, São Paulo State, Brazil. 4 School of Civil Eng., PUC-Campinas, Campinas City, São Paulo State, Brazil. 5 Department of Materials, Federal Institute of São Paulo (IFSP), São Paulo City, São Paulo State, Brazil (*) expedito@fem.unicamp.br ABSTRACT This study aims to determine and present the results of an experimental study of Synthetic (polypropylene) Fibers Reinforced Concrete (SFRC), in levels of 0.33% - 3kg/m 3, 0.50% - 4.5kg/m 3, and 0.66% - 6kg/m 3, using cement CP V ARI, at ages 28 and 88 days after specimens molding. The specimens were exposed for 60 days in aggressive environment (in solution of water and 3% of sodium chloride), after 28 days. The bending toughness tests were performed in prismatic specimens of 150x150x500mm. We used the standards ASTM C1609/C1609M-10 and JSCE-FS4/1994. The toughness factor values of the specimens in aggressive environment were the same to those obtained in normal environment (in air). Keywords: Toughness in bending, concrete reinforced with polypropylene fibers. INTRODUCTION A very important property of materials is the fracture toughness. Through this property is possible to select materials, design parts and assess industrial systems in operation accused the presence of cracks (Torrico, 2006). The addition of fibers to concrete is used primarily to minimize the appearance of cracks caused by the shrinkage of the plastic concrete, caused by ambient temperature and heat of hydration of cement. The fibers when incorporated into the concrete are responsible for the transformation of fragile material characteristics to a pseudo-ductile material. Bayasi and Mcintyre (2002) investigated by experimental research the quantification of the effect of polypropylene fibers and silica fume into the concrete shrinking plastic. The fibers have the ability to reduce the opening of the cracks by promoting retention of water and still allow concrete reinforced with fibers to withstand high tensile stresses, with high capacity for deformation in the post-cracking. Li (2011) emphasizes that the type of fibers can be seen with different criteria. From the standpoint of size, the fibers can be classified as micro and macro. The diameter of macrofibra is in the range of 0.2 to 1 millimeter and microfibers are in a range of a few tens of micrometers. Basically, microfibers are effective in containing microcracks. In Brazil, research is undertaken on the application of fibers with prominent researchers Agopyan (1991), Armelin (1992), Figueiredo (1997), Nunes (1998), Guimarães (2003), Carnio (2009), among others. The work exhibited is only artificial fibers and will be presented information on synthetic fibers and polypropylene results and discussion of concrete reinforced with polypropylene fibers. 1. SYNTHETIC FIBERS Synthetic fibers play an important role in the field of construction, both in financial terms, relatively low cost compared to other types of fibers, both in their mechanical strength. According to Bentur and Mindess (2005) Synthetic fibers (polymers) have become more attractive for reinforcement of mortars and concrete, with a diversity of services where they are applied materials and products made from polymers. The definition of Callister and Rethwisch (2010) polymers consisting of a large number of molecular chain, where each of these chains can bend, twist and curl, leading to extensive twist of the molecules of neighboring ICEM15 1

2 Porto/Portugal, July 2012 chains. Still, Callister (2010) confirms that these random interweaving spirals and are responsible for important mechanical properties of polymers. Unlike natural fibers directly obtained from nature, derived from vegetable, animal or mineral oils, synthetic fibers are obtained from the processing of natural polymers or by modification of synthetic polymers. Examples of synthetic polymeric fibers mentioned by Carnio (2009) are fibers of polypropylene, polyester, polyethylene and polyamide. The synthetic polypropylene fibers are sorted by Bentur and Mindess, 2005 into two types according to their geometry: monofilament and fibrillated. The Figure.1 shows the fibrillated polypropylene fibers used in this study. Fig.1 - polypropylene fibers of fibrillated type According Bayasi and Zeng (1993) the concrete with polypropylene fibrillated fibers have wide application in industrial flooring and construction elements of the wall and slab. These applications are driven by improvements in the properties of cracks and ductility and impact resistance Fiber reinforced concrete) Soranakom and Mobasher (2009) report that fiber reinforced concrete (FRC) can be considered a quasibrittle material composed of concrete, and fibers. The fibers which are randomly distributed in the concrete matrix containing as fissures. The main areas of applications of FRC are industrial flooring, coatings tunnels, precast elements, among others. According to Naaman (2007), fibers when used in concrete structures provide a contribution in improving the properties, among which is the ability of tensile, shear, bending and ductility. Jiang and Banthia (2010) studied the influence of tensile toughness in bending the specimens with different dimensions with concrete reinforced with polypropylene fibers, with three dose rates of 3, 4.5 and 6kg/m3. The dimensions of the specimens were tested correspond to the dimensions of 100x100x350mm and 150x150x500mm respectively used and the test procedure from the standard ASTM C1609/C1609M-10. The sizes of the specimens results indicated differentiates and tenacity. The specimens with the highest resistance smaller than the largest dimensions in proportion to the increased dosage of fibers. 3. MATERIALS AND METHODS The materials and procedures were based on studies and compared to Jiang and Banthia (2010). It will therefore be described in the materials and procedures of the tests to assess the structural stability of each sample. The literature review guided and defined strategies for choosing the binomial "tests and materials," which allowed the incorporation of polypropylene fibers. The study was a test of toughness, tensile bending specimens concrete reinforced with polypropylene fibers. 3.1 Materials used The purpose of the study is to examine the potential of the materials used to construct the reference concrete and the concrete reinforced with fibers of polypropylene which are described below, in order to characterize each component. 2

3 The sequence of procedures adopted in the production of concrete reference to obtain the trace reflects 1:1.85:2.77:0.55, following this order of the materials used per cubic meter dash in: cement, 385 kg sand, 713 kg, gravel, kg water, 212 liters; additive (0.16%), liters. In preparing the composite concrete reinforced with fibers of polypropylene as the work suggested Jiang and Banthia (2010), content and dosage shown in Table 1. Table.1 - fiber contents (%) and rates (kg / m³) Composite Fiber contents (%) - Dosage (kg/m 3 ) CRFP Two specimens were made for each type of prismatic fiber content dimensions 150x150x500mm in steel molds. After molding the specimens were kept in a moist chamber for 28 days, and then transferred to a laboratory environment with an average temperature of 25 C, to remain for another 60 days in half normal (air) and aggressive (in aqueous solution of 3% by weight sodium chloride). 3.2 Testing of tensile toughness in flexion The study was conducted following the recommendations in the implementation of 1609/C1609M-10 controlled loading and JSCE-SF with the aim of determining the flexural toughness factor. The following is transcribed the test procedures: 1) In each specimens is marked on the upper face of the measures corresponding to the points of load application; 2) After positioning the specimens in the press is the adjustment of the support yoke, which is coupled on the side of the specimens aligned to the knife, predetermined markings, shown in Fig. 2. Fig.2 - YOKE Device for fixing the LVDT specimens digits. 3) Following the LVDT supported YOKE the system is reset and the data logger is calibrated, and ending the following test procedures the specimens is subjected to loads causing vertical displacements at the center of the specimens. The flexural toughness factor is calculated by Equation (1) and will be given with three significant In which: FT = flexural toughness factor in MPa; T b = flexural toughness in N.mm; tb = tb vertical displacement equal to L/150, mm; L = distance between the pivoting specimens, in mm; b = average width of the specimens section, mm; d = average height of the specimens, in the section of rupture, in mm. ICEM15 3

4 Toughness factor (MPa) Porto/Portugal, July 2012 RESULTS Toughness tests were performed on universal testing machine EMIC mechanics, model DL-30000F. According to ASTM C1609/C1609M-10, the tenacity can be measured by the factor of toughness. The following Table 2 and Fig. 3 show the results recorded in toughness test. Table.2 - Factor average toughness (MPa) Factor toughness (MPa) Type of concrete 28 days 60 days on display through Normal Aggressive CRFS 3kg/m 3 1,03 1,53 1,54 CRFS 4,5kg/m 3 1,22 1,18 1,20 CRFS 6kg/m 3 1,03 1,21 1,20 2,0 1,8 1,6 28 days in humid chamber 60 days in normal environment 60 days in aggressive environment 1,4 1,2 1,0 0,8 0,6 0,4 0,2 0,0 SFRC 3kg/m³ SFRC 4.5kg/m³ SFRC 6kg/m³ Type of concrete Fig. 3 - Toughness factor results for the Synthetic (polypropylene) Fibers Reinforced Concrete (SFRC) Fig. 3 illustrates the results for tests on concrete reinforced with polypropylene fibers using three levels of broken fibers at different ages and means. You can see that the samples related to the age of 60 days exposed in normal and aggressive media at a dose of 3 kg/m³ obtained higher values, only 28 days in a moist chamber there was a drop in the results. However, dosages of 4.5 and 6 kg/m³ at the ages of 28 days exposed in a moist chamber and exposed to 60 days in normal and aggressive media kept leveling results, noting only that the results of the samples regarding the dosage of 6 kg/m³ to 28 days exposed in a moist chamber there were reductions in the results. 4

5 CONCLUSION This study shows that there are substantial differences on the mechanical properties of different urogynecology meshes. Further tests should be performed in order to analyze other mechanical properties, such as flexural properties. ACKNOWLEDGMENTS The authors thank UNICAMP (University of Campinas) and IFPA (Federal Institute of Education, Science and Technology). REFERENCES AMERICAN SOCIETY FOR TESTING AND MATERIALS. C1609/C1609M-10: standard method for flexural performance of fiber-reinforced concrete (using beam with third-point-loading). West Conshohocken, Pennsylvania, United States of America, p. BAYASI, Z.; MCINTYRE, M. Application of fibrillated polypropylene fibers for restraint of plastic shrinkage cracking in silica fume concrete. American Concrete Institute. Materials Journal, V. 99, Nº 4, July-August 2002, p BAYASI, Z.; ZENG, J. Properties of polypropylene fiber reinforced concrete. American Concrete Institute. Materials Journal, V. 90, Nº 6, November-December 1993, pp BENTUR, A.; MINDESS, S. Fiber reinforced cementitious composites. Elsevier Applied Science. New York, USA, CALLISTER, W. D.; RETHWISCH, D. G. Materials science and engineering: an introduction. 8 th Ed.; John Wiley and Sons, United States of America, CARNIO, M. A. Propagation of fatigue cracking of reinforced concrete with low fiber content. Faculty of Mechanical Engineering, University of Campinas, 2009, 145p. Thesis (Ph.D.). JAPAN SOCIETY OF CIVIL ENGINEERS. JSCE-SF4: method of tests for flexural strength and flexural toughness of steel fiber reinforced concrete. Concrete Library International. Nº 3, Part III-2. June p JIANG, Z; BANTHIA, N. Size effects in flexural toughness of fiber reinforced concrete. ASTM: Journal of testing and evaluation. Vol. 38, Nº 3. January, p. 1-7 Li, Z. Advanced concrete technology. John Wiley e Son, Inc. New Jersey, NAAMAN, A. E. High performance fiber reinforced cement composites: classification and applications. International Workshop. Cement Based Materials and Civil Infrastructure. University of Engineering and Technology. Karachi, Pakistan. December, p SORANAKOM, C; MOBASHER, B. Flexural design of fiber-reinforced concrete. American Concrete Institute. Materials Journal. September-October V. 106, Nº 5, p TORRICO, I. F. A. Fracture toughness under conditions elasto-plastic specimens with non-standard API 5L steels: experimental and numerical analysis. Campinas: School of Mechanical Engineering, University of Campinas, 2006, 160p. Thesis (Ph.D.). ICEM15 5