# Dynamic Response of Reinforced Recycled Aggregate Concrete Pavement under Impact Loading
## Experimental Methods
### Description of RCP Specimens  
Five types of 1000 mm square RCP slab specimens with different longitudinal reinforcement spacing (100 and 150 mm), thickness (60, 70, and 80 mm), and RAC replacement ratio (0 and 100%) were designed for the experimental program. The RCP specimens were named by thickness (cm), type of concrete, the location of the impacting load, and additional information (1 meant the longitudinal reinforcement spacing was 100). For example, two types of concrete were used in the experimental program: NAC was named N, and RAC was named R. M represents that the RCP specimen was subjected to impact load at its mid-point. The details of all RCP specimens are summarized in Table 5, and their reinforcement layouts are shown in Figure 2.  
All RCP specimens adopted the single-layer reinforcement scheme with equal amounts of reinforcement in both planar directions, resulting in two layers of bars. The diameter of reinforcement bars was 8 mm, and the rebar spacing within the RCP specimens ranged from 100 mm to 150 mm. For slab thicknesses of 60 mm, 70 mm, and 80 mm, the thicknesses of concrete protective cover from the bottom surface were 25 mm, 30 mm, and 35 mm to ensure that the steel bars were located in the middle of the slab. According to MT/T 5004-2010, the single-layer steel bars should be located in the lower 1/3-1/2 thickness of the slab [2]. The transverse and longitudinal steel pieces were bundled by steel wires  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Type of**} & \multicolumn{2}{c}{**Compressive Strength, 28 Days**} & \multicolumn{2}{c}{**Split Tensile Strength, 28 Days**} & \multicolumn{2}{c}{**Flexural Strength, 28 Days**} \\ \cline{2-7}  & **Mean** & **Standard** & **Mean** & **Standard** & **Mean** & **Standard** \\  & **(Mpa)** & **Deviation** & **(Mpa)** & **Deviation** & **(Mpa)** & **Deviation** \\ \hline NAC & 46.80 & 1.694 & 3.55 & 0.141 & 5.64 & 0.303 \\ RAC & 48.28 & 1.236 & 3.21 & 0.172 & 5.44 & 0.376 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Mechanical properties of concrete.  
Figure 2: Size and reinforcement layout of RCP specimen (mm).  
to create a continuous mesh, and those steel meshes were fixed on the cement cushion block during vibration to achieve an accurate positioning in the slab. Short bars of 20 mm length and 8 mm diameter were welded at both ends of all reinforcement bars to enhance anchoring capacity and ensure sufficient reinforcement (Figure 3).  
To ensure consistency and good quality of each RCP specimen, the concrete was mixed and cured in-house using a 60 L single horizontal-axis forced mixer in the Concrete Materials Laboratory. In addition to the RCP specimens, three 100 mm \(\times\) 100 mm \(\times\) 100 mm cube samples were cast from the same batch to characterize the compressive strength of the concrete material. The cube samples and RCP specimens were cured in natural environment conservation, and watered in the first 7 days to ensure the strength of concrete and prevent cracks. The average compressive strength of cube specimens was measured synchronously after the impact experiment, which is listed in Table 5.