## 4 Experimental and Analysis Result
Figure 19 compares the strength reduction rate for the overall average adhesion strength (entire tile) and the average adhesion strength of the individually sectioned tiles (with measurable adhesion strength) based on changing AR conditions. As a result of analyzing the pieces with secure bonding, the adhesion strength of the AR 60 \(\pm\) 2% condition was an average of 0.69 N/mm\({}^{2}\), AR 80 \(\pm\) 2% was an average of 0.61 N/mm\({}^{2}\), and AR 100% was an average of 0.83 N/mm\({}^{2}\). In the case of AR 100%, all of the specimens showed an adhesion strength performance that met the ISO standard requirement. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**AR Conditions**} & \multicolumn{3}{c}{**Results (Average)**} \\  & **60 \(\pm\) 2\%** & **80 \(\pm\) 2\%** & **100\%** \\ \hline
40 tile pieces adhesion strength average & 0.25 N/mm\({}^{2}\) & 0.31 N/mm\({}^{2}\) & 0.76 N/mm\({}^{2}\) \\ Fully adhered pieces & 14.7 (36.7\%) & 21.7 (54.2\%) & 37.3 (93.3\%) \\ Average adhesion strength of the fully & 0.69 N/mm\({}^{2}\) & 0.61 N/mm\({}^{2}\) & 0.83 N/mm\({}^{2}\) \\ adhered pieces & ISO standard (0.5) above & 10 (25\%) & 12 (30\%) & 30 (75\%) \\ Entire tile/stable adhesion pieces ratio (\%) & 68.5\% & 58.8\% & 80.6\% \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Overall adhesion strength result per spot-bonding surface area condition. Figure 17: Comprehensive comparison of different AR-conditioned tile pieces. As can been seen in Figure 19, both AR 60 \(\pm\) 2% and AR 80 \(\pm\) 2% had a significant variation of the comparison (an indication that a majority of the surface area was a cavity), whereas, in contrast, AR 100% had a minimal difference of adhesion strength when comparing the values of the entire tile to those with stable adhesion. Through these results, it was shown that if AR 100% was secured, it was possible to secure the standard adhesion strength for about 80% of the entire tile surface, and when the adhesion area (AR) was around 80%, it was possible to secure the standard adhesion strength with only about 30% of the entire surface, and when AR was around 60%, only 25% of the entire tile could achieve stable adhesion. The experimental demonstration conducted in this study was performed using a commonly used adhesive material and tile base in Korea, compliant with the material specifications and regulations of both the ISO standards and KS (Korean standard). However, further investigation of different tile bases and adhesives must be conducted using the evaluation regime and guideline of this study to propose an installation guideline and standard for the spot-bonding method of tiles. While the quantitative results of this experiment are not yet expected to be used as a reference for other countries, it is hoped that  
Figure 19: Adhesion strength difference between the averaged and individual adhered pieces relative to the common adhered points. Figure 18: Average adhesion strength change linear regression based on the spot-bonding surface area. the methodology is replicable and highly recommended to be conducted in other nations for a better understanding of their respective situations on the spot-bonding installation of tiles.