Statistical analysis of electrical resistivity as a tool for estimating cement type of 12-year-old concrete specimens

Statistical tests on values of concrete resistivity can be used as a fast tool for estimating the cement type of old concrete. Electrical resistivity of concrete is a material property that describes the electrical resistance of concrete in a unit cell. Influences of binder type, water-to-binder ratio, moisture and temperature can be detected by changes in resistivity. Data on resistivity about relatively young concrete are available for a wide range of compositions. Measurements are performed in a non-destructive manner with either the Wenner-probe or the Two Electrode Method. The relationship between resistivity and concrete durability is still under research. This paper shows that statistical analysis of electrical resistivity might be a useful tool for estimating the concrete binder. In 1998, concrete specimens with several cement types and water-to-binder ratio were cast and then exposed to salt/dry cycles for 26 weeks. Afterwards, they were left unsheltered in The Netherlands for most part of the following 12 years. In 2010, the identification labels became unreadable. Nested Factorial Design (NFD) and Kolmogorov-Smirnov Two Sample Test (KS) were applied on values of concrete resistivity obtained from measurements on concrete specimens after 2.5 and 12 years, respectively. Results showed that cement type had the strongest influence on values of resistivity. Also, the probability found in 1995 remained recognizable even after 12 years. This procedure may have significant value for concrete scientists investigating old concrete structures that lack proper documentation on the concrete composition. © 2012 Taylor & Francis Group