## 2 Electrical Resistivity/Impedance Measurement: Is It Really that Simple?
### AC Measurement of Electrical Resistivity
#### 2.2.3 Other Methods Exploiting AC Excitation
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Reference** & **Specimens** & **Electrodes** & **Material** & **Additions** & **Frequency** \\ \hline [PERSON] et al. [96] & Cylinders: 102 mm & Surface electrodes & Concrete & Fly ash, silica fume, metakaloin, ground glass, and sugarcane bagasse ashes & 13 Hz \\  & (diameter) \(\times\) 205 (height) & Surface electrodes & Concrete & - & 13 Hz \\ [PERSON] et al. [81] & Cylinders: 102 mm & Surface electrodes & Concrete & - & 13 Hz \\  & (diameter) \(\times\) 205 (height) & Multi-electrode array (14 electrodes, equally spaced at 20 mm) & Concrete & - & 2 Hz \\ [PERSON] et al. [99] & Slabs: \(900\times 700\times 150\) mm & & Concrete & - & (square wave) \\ [PERSON] and [PERSON] [12] & - & Surface electrodes (RESI system) & Concrete & - & 40 Hz \\ [PERSON] et al. [100] & Cylinders: 100 mm & & & & \\  & (diameter) \(\times\) 200 mm & Surface electrodes (Florida method resistivity meter) & Concrete & - & 13 Hz \\  & (height) & Cubes: 150 mm side & & & \\ [PERSON] and [PERSON] [16] & Cylinders: 100 mm & Surface electrodes (commercial resistivity meter) & Concrete & - & 13 Hz \\  & (diameter) \(\times\) 200 mm & & & & \\ [PERSON] et al. [102] & Cylinders: 101.6 mm & Surface electrodes (commercial resistivity meter) & Concrete & - & - \\ [PERSON] [103] & Cubes: 250 mm (side) & Surface electrodes (commercial equipment) & Concrete & - & - \\ [PERSON] et al. [104] & Cylinders: 101.6 mm & & & & \\ [PERSON] et al. [104] & (diameter) \(\times\) 203.2 mm & Surface electrodes (CNS RM MXII resistivity meter) & Concrete & - & 13 Hz \\  & (height) & & & & 97 Hz \\ [PERSON] et al. [105] & (diameter) \(\times\) 200 mm & Reinforcement rebars & Concrete & - & (square wave) \\  & (height) & & & & \\ [PERSON] et al. [35] & Prisms: & Surface electrodes & Concrete & - & - \\  & & & & \\  & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: AC measurements with 4-point probe method. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Reference** & **Specimens** & **Electrodes** & **Material** & **Additions** & **Frequency** \\ \hline [PERSON] and [PERSON] [88] & Cylinders: 100/150 mm & & & & \\ [PERSON] and [PERSON] [88] & (diameter) \(\times\) 200/300 mm & Surface electrodes & Concrete & - & - \\  & (height) & & & & \\ [PERSON] et al. [31] & Prisms: 100 \(\times\) 100 \(\times\) & - & Concrete & Slag (50\% and 70\% & - \\  & 170 mm & & & by mass) & - \\  & Cylinders: 100 mm & & & & \\ [PERSON] et al. [94] & (diameter) \(\times\) 200 mm & Surface electrodes & Concrete & Fly ash, HVFA, & \\  & (height) & & & fine limestone powder & - \\ [PERSON] et al. [101] & Cylinders & Surface electrodes & Concrete & HVFA and fine & - \\ [PERSON] and & Beams: 100 \(\times\) 200 \(\times\) & Surface electrodes & Concrete & Fibers & - \\ [PERSON] [98] & 1500 mm & & Surface electrodes & Concrete & - & - \\ [PERSON] et al. [108] & - & Surface electrodes & Concrete & - & - \\ [PERSON] [109] & Slabs: 400 \(\times\) 300 \(\times\) 100 mm & Surface electrodes & Concrete & - & - \\ [PERSON] [110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 1