Instrumented System for Analysis of Concrete Resistivity
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Instrumented System for Analysis of Concrete Resistivity Karen Sarai Chan Blanco1, Víctor Manuel Jesús Moo Yam1, Tezozomoc Pérez López1, José Ruben Lagunas Jiménez2. 1
Centro de Investigación en Corrosión, Av. Agustín Melgar s/n, P. O. Box, San Francisco de Campeche, Campeche, México. 2
Facultad de Ingeniería, Campus V, Predio s/n x Av. Ing. Humberto Lanz Cárdenas y Fracc.
Ecológico Ambiental Siglo XXIII, Colonia Ex Hacienda Kalá, C.P. 24085. San Francisco de Campeche, Camp., México.
ABSTRACT As is well known, the corrosion of embedded steel reinforced depends strongly of the concrete resistivity, which is related directly with the water contained into its porous network. Environment plays an important role on resistivity, due to have a direct correspondence with the relative humidity and temperature. In these terms, ingress or output of water is favored or hampered by the environmental parameters, as well as its fluctuations. This work presents a proposal of instrumented system to generate a map of electrical resistivity at concrete samples by using superficial and embedded electrodes. Mathematical analysis of equivalent circuit revealed the importance of the impedance of electrodes utilized, to simplify measures. Concrete samples were exposed to different relative humidity focused to try to obtain the relation between relative humidity and resistivity. An array of two electrodes distributed in a matrix was manufactured to apply a signal of direct current at first electrode and measure the resultant current at second electrode. The system applies a programmed sequence of switch to turn on and turn off to realize measurements over established zone and, in this form, allows identify zones with potentials gradients. Also, do easy the monitoring of concrete resistivity evolution in function of time and humidity conditions. INTRODUCTION The ability to continuously monitor in real time the concrete, can allow a more informed evaluation of the current and future performance of the reinforced concrete structure [1].The resistivity depends largely on the degree of saturation of the pores of the concrete, and in a lesser degree of hydration of the paste and the presence of salts dissolved in the aqueous phase [2].The electrical resistivity tomography represents one of the widely used geophysical techniques for the exploration of the subsurface. Recently, this method has been demonstrated to be an efficient reconnaissance tool not only for monitoring degradation status of wall and foundations of buildings [3]. There are two main types of test to determine the value of resistivity, direct current or alternating current [4,5]. This paper presents the development of a resistivity measurement system in concrete by means of two embedded electrodes, applied to the monitoring of resistivity of samples exposed in different conditions of relative humidity.
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