Influence of the Type of Strain Measurement Device and of the Speed of Loading and Unloading of the Testing Machine in the Determination of the Static Modulus of Elasticity of the Concrete

Abstract

This paper presents a comparative analysis of the results obtained for testing the tensile modulus, through a collaborative program of tests on hardened concrete, developed at the School of Civil Engineering, Federal University of Goiás, in the Department of Technical Support and Control of Furnas central Electric Company SA and Carlos Campos and Construction Consultancy Limited., to identify and assess the influence of some factors involved in the test results the elastic modulus. This test was performed according to ABNT NBR 8522:2008, loading plan initial tangent modulus characterizing the deformation of concrete subjected to the stresses of 0.5 MPa and 30% of the breaking load. For this, we sought to determine the outcome of the module, the influence of strain gauge (compressômetro mechanical, electrical bonding surface extensometer extensometer and electric external fixation) and rate (0.3 and 0.6 MPa/s) bodies on the test piece cylindrical size 150 mm x 300 mm C30 concrete class. We performed 60 trials considering the results with satisfactory performance in the statistical techniques of the program. It was concluded that the strain gauge type of load and speed significantly influenced the results of elastic modulus. Moreover, it is noteworthy that the bodies of the test piece size 150 mm x 300 mm concrete Class C30, tested with loading speed of the testing machine of 0.3 MPa/s presented the results with the highest dispersion.