A quantitative analysis of the geometric effects of reinforcement in concrete resistivity measurement above reinforcement Young-Chul Lim a , Takafumi Noguchi b , Chang-Geun Cho c,⇑ a Department of Architecture, Catholic University of Daegu, 13-13 Hayang-ro, Hayang-eup, Gyeongsan-si, Gyeongsangbuk-do, Republic of Korea b Department of Architecture, Faculty of Engineering, The University of Tokyo, Tokyo, Japan c School of Architecture, Chosun University, 309 Pilmun-daero, Dong-gu, Gwangju, Republic of Korea highlights  This work presents the estimation of concrete resistivity above reinforcement.  Geometric effect (GE) predicts quantitatively the effect of reinforcement.  The prediction of GE is based on a resistivity method.  Apparent resistivity rate estimates the concrete resistivity above reinforcement. article info Article history: Received 14 January 2015 Received in revised form 4 March 2015 Accepted 5 March 2015 Available online 17 March 2015 Keywords: Corrosion Reinforcement Geometric effect Apparent resistivity Concrete resistivity Durability Nondestructive technique abstract This study aims to quantitatively estimate the geometric effect of steel bar on the resistivity measure- ment above reinforcement as a method of evaluating concrete resistivity. For this purpose, the geometric effect is evaluated by the resistivity estimation model (REM) that estimates the apparent resistivity above the reinforcement. This REM as a mathematical model reflects the resistivity of concrete and reinforce- ment, as well as the cover depth, the bar diameter, and electrode intervals. Based on this evaluation, this study proposes a geometric effect (GE) rate, which is the quantitative index determined by the geometric factors of reinforcement. It also experimentally examines the applicability of the apparent resistivity rate to diagnose the concrete resistivity. Based on the results of this study, the GE rate is expected to be useful for estimating the geometric effects of reinforcement. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction The corrosion state of reinforcing bar in concrete structures is accelerated or restrained depending on the environmental factors that surround the reinforcement. Factors that affect corrosion sta- tus include internal elements, such as dissolved oxygen and ions, water, pH, and temperature within the pores in concrete [1]. The resistivity of the concrete that surrounds the reinforcement is, therefore, dependent on the corrosive environment and can be used as an index for evaluating the durability of concrete structures. As for the methods used to diagnose corrosion deterioration, the electrochemical techniques of the half-cell potential and polariza- tion resistance have generally been used [2–4]. However, these methods require local destruction such as cover concrete chipping. On the other hand, the resistivity method for estimating con- crete resistivity provides a nondestructive technique for evaluating the corrosive environment [5]. However, the apparent resistivity measured above the reinforcing bar cannot be used for estimating the concrete resistivity because the effect of reinforcing bars has not been considered in such approaches. The exact estimation of concrete resistivity therefore requires the method that provides a quantitative analysis of the reinforcement alone. Although various studies on the quantitative analysis [6–9] of the influence of reinforcement have been carried out, the obtained results have not been verified experimentally. The objective of this study is to quantitatively estimate the geo- metric effect of reinforcement on the resistivity and develop the convenient method to estimate concrete resistivity. To this end, the geometric effect (GE) rate generated by the resistivity estimation model (REM) [10] is proposed to represent the relationship between the apparent resistivity, which is affected http://dx.doi.org/10.1016/j.conbuildmat.2015.03.045 0950-0618/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +82 622307023; fax: +82 622307155. E-mail address: chocg@chosun.ac.kr (C.-G. Cho). Construction and Building Materials 83 (2015) 189–193 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat