# Effect of Injecting Epoxy Resin Adhesive into Cement Mortar on Tile Adhesion Performance
## 4 Conclusions  
The adhesion performance of tiles with the injected epoxy resin adhesive was evaluated and the following conclusions drawn:  
1. As a result, in the case of using an epoxy resin adhesive within the scope of this study, the adhesive strength improved up to about two times compared to that of using the existing dry cement mortar under the air curing condition. However, it was confirmed that the adhesion strength decreased by up to about 30% compared to using dry cement mortar under water curing and freeze-thaw conditions. Meanwhile, in salt immersion and laitance conditions, it showed about four and two times higher adhesion strength than dry cement mortar, respectively.
2. The workability and permeability of the epoxy resin adhesive were enhanced at a solvent mixing ratio of 0.5 wt%. It is believed that this epoxy adhesive not only penetrated the interfaces of the tiles, mortar, and concrete, but also the mortar itself, thus improving the mechanical adhesion between each interface. This characteristic is potentially effective in improving the adhesion performance of porcelain and polished tiles with small pores, which make it difficult for the mortar to penetrate and mechanically adhere to the tiles.
3. In addition to the improved mechanical adhesion between the tiles and mortar, the epoxy resin reinforcement also minimized the deterioration of adhesion due to shear stress by reducing the moisture evaporation and drying shrinkage of the mortar, which consequently reduced the shrinkage of the tiles themselves. In particular, the epoxy resin was expected to improve the adhesion performance of the large-sized tiles that are currently in demand because these tiles experience greater shear stress from shrinkage.
4. The vulnerability of epoxy to moisture was observed under water and freeze-thaw curing conditions. However, based on the evaluation of the adhesion performance after standard air curing and salt immersion, the adhesion performance should be maintained if a stable level of performance is achieved by adequate air curing prior to exposure to harsh environments. However, further investigation of the effect of long-term exposure to harsh environments on the durability is required.  
Conceptualization, S.L. ([PERSON]), S.L. ([PERSON]) and G.K.; Methodology, S.L. ([PERSON]), S.L. ([PERSON]) and M.S.; Validation, S.L. ([PERSON]), S.L. ([PERSON]), G.K., M.S., G.C., J.L. and J.N.; Formal analysis, S.L. ([PERSON]) and G.K.; Investigation, S.L. ([PERSON]) and G.K.; Resources, S.L. ([PERSON]) and S.L. ([PERSON]); Data curation, S.L. ([PERSON]), S.L. ([PERSON]), M.S.; Writing--original draft preparation, S.L. ([PERSON]), S.L. ([PERSON]), G.K. and M.S.; Writing--review and editing, S.L. ([PERSON]), S.L. ([PERSON]), G.K., G.C. and J.L.; Visuialization, S.L. ([PERSON]), S.L. ([PERSON]) and G.K.; Supervision, G.K.; Project administration, S.L. ([PERSON]) and G.K.; Funding acquisition, S.L. ([PERSON]) and G.K. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the Korea Agency for Infrastructure Technology Advancement (KAIA) grant funded by the Ministry of Land, Infrastructure and Transport (Grant 20 SCIP-B146646-03).  
The authors declare no conflict of interest.