# Performance Evaluation of Bedding Sand and Load Transfer Characteristic of Concrete Block Pavements
## 3 Results
### Evaluation of Joint Performance  
#### 3.2.1 Load Transfer Characteristics of Joint  
The LTE is evaluated by means of FWD at joints in joined concrete pavements or cracks in continuously reinforced concrete pavements. For concrete block pavements, discontinuity is obtained through the joint sand filled between block elements with relatively small dimensions. In general, the diameter of the widely used loading plate of FWD is 300 mm, which is difficult to apply to concrete block pavements; therefore, the load transfer characteristics at joints have not been studied sufficiently. Therefore, we evaluated the load  
Figure 4: Method of measuring the LTE and concrete block rotation. Figure 3: Pavement sections and experimental setup. transfer characteristics of joints using a 90 mm loading plate. Manufactured sand was used for the experiment. First, the difference in load transfer characteristics was examined when the four selected blocks were laid in a stack pattern. Figure 5 shows the LTE by block shape for the stack pattern. It was found that the LTE increased in all block shapes as the degree of joint filling increased, and the minimum difference between 0% and 100% joint filing was approximately three times. When the joint sand was 100% filled, the Uni and Dasuri blocks showed similar load transfer performance, which was approximately 5% higher than that of the square and rectangular blocks. Figure 6 shows the relationship between the shape factor and LTE: a proportional relationship is seen. It can be seen that the load transfer characteristic between blocks is affected a bit by the block shape, but it is significantly affected by the degree of filling of the joint sand. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multicolumn{4}{c}{**Vertical Stress, kPa**} \\ \cline{2-6}  & **50** & **100** & **150** & **Internal Angle** \\ \cline{2-6}  & \multicolumn{4}{c}{**Shear Strength, kPa**} \\ \hline \multirow{4}{*}{Sand type} & Quartz sand & 20.67 & 41.34 & 77.45 & 23.99\({}^{\circ}\) \\ \cline{2-6}  & Manufactured & & & & \\ \cline{2-6}  & sand & 19.08 & 39.75 & 71.89 & 22.72\({}^{\circ}\) \\ \cline{2-6}  & River sand & 22.26 & 44.52 & 82.22 & 25.01\({}^{\circ}\) \\ \hline \multirow{2}{*}{0.6 mm passing ratio (River sand)} & 60\% & 25.44 & 47.70 & 74.73 & 26.23\({}^{\circ}\) \\ \cline{2-6}  & 40\% & 28.62 & 50.88 & 79.50 & 26.96\({}^{\circ}\) \\ \cline{2-6}  & 20\% & 27.03 & 50.88 & 76.32 & 26.24\({}^{\circ}\) \\ \hline \multirow{2}{*}{0.075 mm content (River sand)} & 1\% & 22.26 & 44.52 & 71.55 & 24.00\({}^{\circ}\) \\ \cline{2-6}  & 3\% & 25.44 & 50.88 & 74.73 & 26.23\({}^{\circ}\) \\ \cline{2-6}  & 5\% & 30.21 & 55.65 & 79.5 & 26.97\({}^{\circ}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Shear strength and internal friction angle according to sand type. Figure 5: LTEs by block shapes. Figure 7 shows the LTE measurements of the rectangular blocks according to construction pattern. The slope of the linear regression trend line was similar in all cases. A slight difference in the LTE by the construction pattern is measured. LTE is determined according to the joint condition. Since the construction pattern is independent of the joint condition, it is determined not to have an effect on the LTE. According to a study by [PERSON] et al. (2006), high vertical deformation occurs when the degree of joint filling is less than 75%, whereas high horizontal deformation occurs when it is 0% ([PERSON] et al., 2006). If the joint is fully filled, the block thickness and bedding material have no impact on the deformation resistance of the concrete block pavement. Figure 8 shows the LTE if the degree of joint filling is the only parameter regardless of the block shape and lying pattern. A linear regression analysis showed a regression coefficient of 0.68, indicating a correlation. According to [PERSON] et al. (2006), if the degree of joint filling is 75% or more, the required LTE is approximately 50% or higher ([PERSON] et al., 2006).