# Experimental Study on the Strength and Durability for Slag Cement Mortar with Bentonite
## 1 Introduction  
It is quite common that concrete structures are located in environments full of pollutant ingredients and chemicals that are harmful to concrete, such as sewer systems, water processing plants, and infrastructure located in marine environments. Maintaining good durability for the structures located in such environments always imposes serious challenges. After physical erosion and mechanical loading, chemical attacks usually are the next main cause of damage to concrete material. After the deterioration of material, such as by its neutralization, the corrosion in ferro-material will further advance due to the presence of sulfate, chloride, and acidic elements in the environment that may combine and worsen the deterioration of the material [1, 2, 3]. The loss of impermeability of concrete material is usually a major problem that causes damage to the concrete structures located in aqueous environments. The neutralization of concrete is usually caused by the permeation of chloride, which gradually deteriorates the concrete, damages its impermeability, and then reduces its strength. Once the water seeps into the material along with oxygen, corrosion occurs on the steel reinforcements. This phenomenon has been reported for decades [4, 5, 6] especially for structures located in aqua-environments. For the reinforcement concrete structures located in aqua-environments, the damage of the structure and material can also be a result of combined effects of the chemical actions of seawater constituents on cement hydration products, crystallization pressure of salts within concrete, corrosion of embedded steel in reinforced or pre-stressed steel cable members when they are exposed to hazardous ingredients, and physical erosion due to the action of waves and floating objects. The corrosion in reinforced steel bars embedded in concrete ismostly due to the intrusion of sea water and oxygen, which penetrates through the small cracks of the deteriorated concrete [7]. Some other factors such as sulfate, chloride, and acidic elements can also worsen the problem. It is important to protect the structures made of reinforced concrete in aqua-environments from damage resulting from the deterioration of concrete and corrosion of steel. Among various methods, the most effective is the improvement of the impermeability of the concrete material. At the same time, the other positive properties of concrete materials, such as their strength, must not be influenced. One of the methods to improve the impermeability of concrete material is the application of pozzolanic material [8; 9] because of its finely divided form (less than 75 \(\upmu\)) and its chemical reactivity with calcium hydroxide when moisture is present. In this way, the larger capillary pores in the mixture are filled and, accordingly, we improve the impermeability of concrete material. Therefore, concrete constructions located in marine environments using slag-cement as binders are popular due to the pozzolanic reactions of the slag material [10; 11; 12]. However, in order to examine if further improvement to the durability of slag cement concrete located in marine environments is possible, a bentonite material was applied in this study. Bentonite has been a renowned material, widely applied for masonry, grout, and sludge solidification works due to its good properties of having fine grains, great moisture absorption capability, and bulking properties when wet. The application of bentonite clay for the stabilization and solidification of sewage sludge containing heavy metals has a very good effect on impermeability [13]. A similar application for permeability reduction to the cut-off wall of dams was also reported [14], where part of the cement was replaced by a bentonite material in the plastic concrete that has a low elastic modulus compatible with the surrounding soil.