# Experimental Study on the Strength and Durability for Slag Cement Mortar with Bentonite
## 1 Introduction
Other applications for bentonite are also under development, such as a study of the light-weight aggregates made from fly ash, where the bentonite was used as a binder material when heat treatment process was applied [15]. In a study of concrete with replacement of cement by bentonite [16], it was found that the water demand in concrete was increased while the compressive strength was reduced with respect to the replacement ratio of bentonite. However in [PERSON]'s study [16], the replacement ratio of cement to bentonite was high, from 20% to 50%, and therefore, it is only suitable for concrete with sufficient strength for low-cost construction. A similar finding for concrete with replacement of cement with bentonite but at a lower ratio of replacement (at most 21%) was presented [17], where they also found that the workability and water absorption decreased with increased bentonite content. In a later study, the waterproofing performance of cement mortar containing bentonite can reached a maximum impermeability pressure 2.37 times that of the reference group [18]. Other applications of concrete combined with bentonite and with other materials like polymer balls or recycled aggregates have also been found [19; 20]. It was found that the mechanical and microstructural properties of such concretes combined with bentonite were comparable to that of plain concrete. In terms of compressive strength, bentonite was also used for high-strength concrete [21], and it was concluded that bentonite can be used in concretes where later-stage strength is required because bentonite results in poor early-stage compressive strength but gives good results in later stages. The authors of [17] and [22] also reported that some strength gain was found with longer curing times, which is a very encouraging finding. Therefore, we aimed to take advantage of bentonite to improve the impermeability properties and find the variation of material characteristics in slag cement. By replacing a small amount of binder (cement and slag) with bentonite material, the investigation focused on the improvement of impermeability and durability for slag cement mortar. The purpose of this study was the improvement of the durability of concrete by utilizing slag cement as a binder in costal and marine environments rather than a cost-saving application by consuming large amounts of bentonite material. In this study, various levels of binding material in a slag cement mortar were substituted by bentonite. This is an alternative scheme to improve the impermeability of the concrete, and because of that improvement, it is also expected to provide better capability for sulfate resistance and adsorption ability for chloride, so that eventually the durability of the concrete material can be improved. During the proportioning design, several water/binder ratios were proposed, and laboratory tests were performed to examine the influence of the addition of the bentonite material on both the basic properties and the enhanced characteristics of the slag cement mortar. To determine the durability of the bentonite-added slag cement mortar, tests of its sulfate resistance capabilities were further performed, where the weight loss, moisture absorption, and penetration of chloride were measured. A series of compressive strength tests were also carried out for the specimens subjected to sulfate corrosion and those not subjected to sulfate corrosion.