However, there are two features worthy of note. Use of the equation for samples passing greater than 4000 Coulombs would introduce large errors. Also, the estimate is consistently greater than the conductivity values measured here. This artifact may be due to the longitudinal component of the current originating from the end of the reinforcement bar used in the Berke and Hicks experiment. This additional current would cause an overestimate of the specimen conductivity, as is demonstrated in Fig. 9 .
Dimensions shown are in units of millimeters.