## 2 Development of Conductive Mortar  
### Experimental Procedure  
#### 2.1.1 Materials  
Various admixtures and chemical agents were mixed with mortar to develop conductive mortar. The admixture is a material that contains its own volume in concrete or mortar volume, and its amount is generally more than 5% of the cement amount. In our case, admixtures should have low resistivity and high specific surface area to lower mortar resistivity; therefore, this study selected activated carbon, bentonite, zeolite, and geopolymer as cement substitutes, which are commercialized as general adsorbents.  
Activated carbon is the most widely used multi-purpose adsorbent and has a large surface area induced by the volume of micropores and mesopores. The main ingredientsare carbon materials such as wood, coal, petroleum coke, and fruit shells. Activated carbon produced through the activation process is mainly used in processes that adsorb gas or vapor, and it is known that activated carbon adsorbs hydrogen the most among commercially available adsorbents. It has a non-polar surface or lower polarity due to oxide groups or inorganic impurities on the surface, and activated carbon is used in the process of dealing with moist gas mixtures or aqueous solutions.  
Bentonite, whose main component is montmorillonite, is a clay mineral. Bentonite is primarily classified into Ca-based and Na-based bentonite according to the type of cation between the mineral structural layers. Na-based bentonite has the properties of dispersed clay, which has a relatively smooth surface, good swelling properties, and excellent gel formation ability when absorbing water. On the other hand, Ca-based bentonite is classified as an aggregated clay with relatively severe irregularities and lower swelling and gel formation abilities. Bentonite, in general, has the property of sucking water between unit layers and swelling, a high ability of gel production while absorbing water, and a large specific area so that bentonite can be used as an adsorption treatment material.  
Zeolite, a generic term for aluminosilicate, has the characteristic of forming a space large enough for molecules to easily enter and exit the material due to a unique pore structure present in the crystal. Zeolite is a crystalline material; thus, its crystal structure is not easily broken even when heated or exhausted. When air is exhausted while heating, the substances adsorbed in the pores are desorbed, and the inside of the pores is emptied. In addition, fine pores are well developed, and reversible adsorption-desorption is possible through heating and exhaust operations so that it can be used repeatedly, and it is widely used in separation processes due to its excellent adsorption-desorption characteristics. Water is well absorbed since it is a material with many fine pores and polarity. Water is not a component of zeolite, but it fills the pores; thus, zeolite is sometimes regarded as a hydrate.  
The geopolymer is an aluminum-based binder that can significantly reduce the amount of CO2 emission during construction depending on various factors [30], which was the primary reason the geopolymer was selected as one of the admixtures in this study. The main materials of geopolymer are fly ash, alkali solution, sodium hydroxide, and sodium silicate; the compressive strength of alkali-activated concrete can generally be as high as 150 MPa without the addition of special admixtures.  
A chemical agent is a material that does not contain its own volume in concrete or mortar volume, and its amount is generally less than 1% of the cement amount. Sodium hydroxide, calcium hydroxide, lithium hydroxide, and sodium chloride were selected to decrease concrete resistivity further and increase pH that helps in better anode consumption, i.e., better CP performance.