## 2 Material and Methods
### Development of Onsite Adhesion Strength Measurement Equipment  
When measuring the adhesion strength of waterproofing sheets adhered to concrete surfaces in the field, it is necessary to measure the force of the sheet peeling vertically from the concrete substrate. However, applying the roller drum peel method can be challenging due to the inability to move the substrate when measuring the adhesion strength of the waterproofing sheets attached to actual concrete walls or floors.  
Among the existing methods, the 90\({}^{\circ}\) peel method ensures that the peel length of the sample and the distance traveled by the crosshead are equal. By drawing a graph depicting the relationship between the crosshead's movement and the distance between the test specimen's backing cellulose fiber reinforced cement (CRC) board as shown in Figure 6, it is observed that the graph precisely follows a 1:1 ratio at a 45\({}^{\circ}\) angle. Based on this observation, the testing equipment was designed assuming the movement of the crosshead at a 45\({}^{\circ}\) angle while peeling the sample. The graph represents a theoretical measurement process during a peel-off of a waterproofing sheet, where the relevant data of the linear regression line for the crosshead displacement relative to the displacement occurring on the CRC board (blue line, marked by blue circles for the intersection points (\(P_{i}\)) for Equation (1)) is demarcated by the red area.  
Therefore, the adopted approach for direct onsite measurements is based on the 90\({}^{\circ}\) peel method or a modified roller drum peel method as the foundation. To propose and develop the onsite adhesion strength measurement equipment, several important factors were considered. Firstly, the movement of the equipment during measurements should not transfer its weight onto the sample. Secondly, lightweight design was prioritized to ensure mobility for onsite measurements. Thirdly, the equipment should allow for immediate confirmation of measurement results at the site. Lastly, the ability to measure the adhesion strength of self-adhesive waterproofing sheets applied to vertical surfaces was a key focus. Taking these considerations into account, a design was created as shown in Figure 7, and a physical prototype was produced as depicted in Figure 8.  
Figure 5: Peel-out test method and measurement result calculation.  
Some important factors that influence the adhesive peel strength include the specimen thickness, the measurement speed, and the onsite temperature. Among these factors, a  
Figure 8: Portable adhesion measurement device; (**a**) portable measuring device, (**b**) portable measuring device program for analysis.  
Figure 6: Graph of the movement–distance correlation between the crosshead and the CRC board during the test.  
Figure 7: Manufacturing design for field equipment.  
higher measurement speed results in a higher adhesive peel strength measurement. In the case of KS F 4934, the specified measurement speed was 100 mm/min, which corresponds to the vertical movement speed of the tension jig. However, for the developed onsite equipment, considering that the tension jig moved at a 45\({}^{\circ}\) angle, the distance traveled by the tension jig differed by \(\sqrt{2}\) due to the trigonometric calculations. To align the measurement speed with the UTM, it was set to 141 mm/min. Preliminary measurement results showed very similar values to the adhesive peel strength measured by the UTM for the same sample. Based on these results, further testing was conducted.  
Comparison of the Adhesion Evaluation According to the UTM Device Measurement Method and the Field Equipment Measurement Method