Fracture behavior study of the concretes produced with crushed stones using wedge splitting method to crack stable propagation

• Grant number: 09/02304-1
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: August 01, 2009
• End date: January 31, 2010
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Nonmetallic Materials
• Principal Investigator: Sebastião Ribeiro
• Grantee: Mateus Botani de Souza Dias
• Host Institution: Escola de Engenharia de Lorena (EEL). Universidade de São Paulo (USP). Lorena , SP, Brazil

Abstract

The principal aim of this project is to stud of the fracture behavior of the concretes, using the wedge splitting method to stable crack propagation. Concrete is the most used material in civil building in the world, for that reason, there are a crescent necessity of the understanding of its mechanical behavior, of the properties of the components and, particularly, the fracture behavior. One of the most important properties of the materials, mainly that with heterogeneous microstructure, is the fracture energy. The fracture energy measures the crack propagation resistance. In Brazil there are a small quantity of the studies in this subject, mainly when it is observed in the high level journal publications. To study the fracture behavior and consequently fracture energy determination of the concretes, the advisable method is the wedge splitting method. This method was recently implanted in the Microstructure of the Materials Engineering Group - Materials Engineering Department in the Federal São Carlos University. This method is being implanted in the Materials Engineering Department of the Engineering School of Lorena - São Paulo University, by the same research that implanted the wedge splitting method in São Carlos University, supported by FAPESP - Process 07/55964-3. The principal advantage of the wedge splitting method is that you can working with samples relatively bigger than conventional method (tree point bending). In this method the aggregate size is shorter compared which fractured area in the samples. Also, in this method, the applied load by the test machine is reduced due to wedge effect, promoting a stable propagation of the crack situation. The concrete sample will be made by Portland cement CPII-E-32, sand, water and crushed stone with size between 4.75 and 9.50 mm as aggregate. Cement/sand ratio will be 1/2 and water/ cement ration will be 0,46. The aggregate quantities will be of 20, 30 and 40% relative to the dry mass (sand plus cement mass). The mixture of the raw materials with water will be realized using an appropriated machine with capacity to 5 liters. The samples will be molded into special steel mold, provide with blade to produce the notch and grooves in the molding operation. After molding, the samples will be cured at 25ºC for 7 days in water saturated atmosphere. Following, the samples will be dried at 50° for 24 hours. To fracture the samples and consequently evaluate the fracture behavior and specially the fracture energy, the samples will be submitted to stable propagation crack using an Universal Test Machine, MTS, working in rigid conditions. The expected results will be load-displacement which will be used to fit up the curves and posterior calculation of the fracture energy. To characterization the fractured surface will be observed the aggregate distribution, aggregate/matrix interface, fractured and debonded aggregate from the matrix. To realize these analyze will be used a stereoscope microscope, optic microscope and scanning electronic microscope. (AU)