# Effect of Injecting Epoxy Resin Adhesive into Cement Mortar on Tile Adhesion Performance
## 2 Materials and Methods
### Experimental Plan and Test Methodology  
Table 2 depicts the experimental plan. The viscosity, curing time, and penetration depth were evaluated using mortar bars, and the permeability was evaluated by a full-scale mockup test to identify the workability and permeability of the epoxy resin adhesive. The viscosity of the epoxy adhesive was measured using a DV2T Touch Screen Viscometer (USA) in accordance with KS M ISO 3219, and the curing time was measured based on the set-to-touch time. The curing time was measured by preparing the epoxy resin with the solvent at various mixing ratios and placing in a mold (\(150\times 75\times 1\) mm). The curing process was observed at 5 min intervals 30 min after the start of curing at constant temperature (\(25\pm 5\,^{\circ}\)C) and humidity (\(50\pm 5\%\)). The permeability of the epoxy adhesive was evaluated by producing a mortar bar (\(40\times 40\times 160\) mm) using DM and attaching a film, as illustrated in Figure 3. The epoxy adhesive was subsequently applied to the top of the mortar bar and maintained for ~20 min. After 20 min, the mortar bar was cut and the penetration depth of the epoxy adhesive was measured. The full-scale mockup was performed \begin{table}
\begin{tabular}{l c c} \hline \hline
**Materials** & **DM** & **AM** \\ \hline Portland cement & 17 & 20 \\ Quartz sand 0.3–0.9 mm & 20 & \\ Quartz sand 0.1–0.6 mm & 60 & 40 \\ Quartz sand 0.1–0.3 mm & & 30 \\ Dolomite filler & 3 & 6 \\ Redispersible polymer powder & - & 4 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Composition of the tile mortar (in wt%). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Evaluation Item** & **Adhesive Used 1** & **Tile Used** \\ \hline Viscosity of the epoxy resin adhesive & & Epoxy resin adhesive & \\ Setting time of the epoxy resin adhesive & (solvent: 0, 5, 10, 15 wt%) & - \\ Permeability of the epoxy resin adhesive & & \\ \hline Flexural and compressive strength of the mortar & & \\ Shrinkage of the mortar and tile & DM & (water absorption \(\leq 10\%\)) \\ AM & Porcelain tile & \\ Adhesive strength of the tile & ERM (solvent: 5 wt%) & (water absorption \(\leq 0.5\%\)) \\  & & Polished tile \\  & & (water absorption \(\leq 0.2\%\)) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Experimental plan. by applying DM on a wall, as shown in Figure 4, and curing it with an acrylic panel placed on the top. Urethane foam was applied to each tile joint to prevent the epoxy adhesive injected at the top from rapidly flowing to the bottom and reducing the permeability. The penetration of the epoxy resin in the mortar was observed by visual inspection. Additionally, scanning electron microscopy was conducted on the resulting specimens to analyze the penetration of the adhesive in the mortar. To identify the mechanical properties of the mortar after reinforcement with the epoxy adhesive, mortar bars (40 \(\times\) 40 \(\times\) 160 mm) were manufactured using DM, AM, and epoxy reinforced DM (ERM), and the flexural and compressive strengths were measured in accordance with KS L ISO 679. The flexural and compressive strengths were determined using loading rates of 50 \(\pm\) 10 N/s and 2400 \(\pm\) 200 N/s, respectively. The shrinkage properties of the tiles and mortar were evaluated using the method shown in Figure 5. Both the tiles and mortar were measured for approximately 1 month after curing for 7 days. To evaluate the adhesion performance of the tiles reinforced with epoxy adhesive, the adhesion strengths under air curing, water curing, freeze-thawing, and salt immersion conditions were measured in accordance with EN 12004. The details of each experiment environment were as follows:  
Figure 4: Test method for the permeability of the epoxy resin adhesive (mockup). Figure 5: Test method for the shrinkage of mortar and tile. Figure 3: Test method for permeability of the epoxy resin adhesive. Air curing: standard condition for 28 d (\(23\pm 2\)\({}^{\circ}\)C, \(50\pm 5\)% RH). Water curing: standard condition for 7 d and water curing for 21 d (\(20\pm 2\)\({}^{\circ}\)C).