3.7. Steady state resistance
The conclusion drawn by Lim et al [1] based on the five month measurements was not optimistic as bentonite-mixed concrete yielded higher grounding resistance value than pure concrete encased steel cages leading to the assumption that bentonite cannot be mixed well with concrete [20].. However, such assumption seems to be wrong when considering the readings taken in long-term. Fig. 4 illustrates the grounding resistance for the first 12 months of measurement. It can be observed that for the first 7 months, the assumption made in Lim et.al [1] was valid [20]. Beyond that period, it seems that 30% bentonite-mixed concrete consistently produced the lowest grounding resistance value. In addition, measured values of other mixtures with the exception of 20% bentonite seem to approach the grounding resistance value of pure concrete encased metal cage beyond that stipulated 7 months. The only anomaly was 20% bentonite because during construction, the steel cage was slightly
damaged which is possibly the reason why its readings are as such. To summarize, 30% bentonite mixed concrete is a promising grounding improvement material based on the 12 months readings. Although there is no clear relation between volume of bentonite and the grounding resistance value, 30% by volume is the ideal proportion when mixing bentonite with concrete.