# Experimental Study on a Prediction Model of the Shrinkage and Creep of Recycled Aggregate Concrete
## 2 Shrinkage and Creep Test of Recycled Aggregate Concrete
### Test Loading Process  
The creep testing of RAC was carried out using a spring-loaded compression creeeper that was loaded with a jack. The load was controlled by a pressure sensor and a digital electronic displacement meter, and the constant value of the load was maintained by the spring reaction force. The creep loading device and shrink test device are shown in Figure 1.  
1. The creep specimens were maintained for 28 days. The prism compressive strength of the specimens under the same conditions was tested before loading. The electronic displacement meter was checked for zero and the initial reading was recorded.
2. After the completion of the alignment, it started loading in time and the creep stress was taken as 60% of the measured prismatic compressive strength.
3. The deformation values of the test piece were read at 1 day, 3 days, 7 days, 14 days, 28 days, 45 days, 60 days, 90 days, 120 days, 150 days, and 180 days after loading, and the shrinkage value of the shrinkage test piece in the same environment was recorded.
4. The load was checked regularly after loading. If the load changed by more than 2%, the correct load was applied, and the nut on the screw was tightened to make up for it.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & & \multicolumn{6}{c}{**Material Consumption/kg:m\({}^{3}\)**} & \multirow{2}{*}{**Compressive**} \\ \cline{3-3} \cline{5-10}
**Group** & & & & & **Natural** & **Recycled** & **Fine** & **Additional** & **Strength/N/mm\({}^{2}\)** \\
**Number** & & **Ratio** & & & **Aggregate** & **Aggregate** & **Aggregate** & **Water** & \\ \hline NAC-I & 0 & 0.527 & 370 & 195 & 1185 & - & 660 & - & 33.3 \\ RAC-50-I & 50 & 0.527 & 370 & 195 & 592.5 & 592.5 & 660 & 22.69 & 31.6 \\ RAC-100-I & 100 & 0.527 & 370 & 195 & - & 1185 & 660 & 45.38 & 32.4 \\ NAC-II & 0 & 0.40 & 500 & 200 & 1086 & - & 611 & - & 35.1 \\ RAC-50-II & 50 & 0.40 & 500 & 200 & 543 & 543 & 611 & 20.8 & 32.3 \\ RAC-100-II & 100 & 0.40 & 500 & 200 & - & 1086 & 611 & 41.6 & 30.9 \\ \hline \hline \end{tabular} Note: Group I was the water–cement ratio (\(\alpha\)/\(\alpha\)) = 0.527 sample; Group II was the water–cement ratio = 0.4 sample. The additional water was calculated to take 3.83% of the weight of the recycled coarse aggregate under consideration of the water absorption rate of the recycled coarse aggregate.  
\end{table}
Table 2: Mix ratio of recycled aggregate concrete (RAC) and natural aggregate concrete (NAC).  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Test Piece**} & \multicolumn{3}{c}{**Specimen Number**} & \multirow{2}{*}{**Specimen Use**} \\ \cline{2-2} \cline{4-5}
**Number** & & & **Phrisan** & **Green** & **Specimen** \\ \hline NAC-I & 3 & 6 & 3 & 2 & A Cube: Cube used to determine the compressive strength. \\ RAC-50-I & 3 & 6 & 3 & 2 & B Prisms: Three were used to determine the ultimate bearing capacity and three were used to determine the elastic modulus. \\ \hline RAC-100-II & 3 & 6 & 3 & 2 & used to determine the elastic modulus. \\ \hline \hline \end{tabular}
\end{table}
Table 3: Number and use of specimens.