# Compressive Behaviors of Prisms Made of Demolished Concrete Lumps and Fresh Concrete
## 4 Conclusions  
In the scope of this experimental study, the following conclusions can be drawn:  
1. The crack development and failure patterns of axially loaded prisms made of DCLs and FC are similar to those of prisms made of FC alone. 2. For the specimens made of FC alone, as the maximum aggregate particle size increases from 20 to 35 mm, there is little change in the \(f_{\text{cv,150}}/f_{\text{cv,300,}}/f_{\text{pr,150}}/f_{\text{pr,200}}\), and \(f_{\text{cy,150}}/f_{\text{cy,300}}\) ratios. 3. A modified formula predicting the compressive strength of compound concrete made of DCLs and FC agrees well with the measured values for prisms, cylinders, and cubes. 4. With increasing DCL fractions, the \(f_{\text{cv,300,CC}}/f_{\text{cy,300,CC}}\) strength ratio generally increases. At replacement ratios from 20% to 40%, the strength ratio of \(f_{\text{pr,300,CC}}/f_{\text{cy,300,CC}}\) related to horizontally cast prisms and vertically cast cylinders is about 1.13. 5. The relative elastic modulus of a prism is very close to that of a comparable cylinder at any given replacement ratio, and there is a linear relationship between the relative elastic modulus and the replacement ratio. 6. The negative effect of including DCLs on the combined elastic modulus is more significant than on the combined compressive strength, and this trend becomes more and more distinct as the replacement ratio increases. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Group**} & \multirow{2}{*}{**Notation**} & \multirow{2}{*}{**Serial**} & \multicolumn{2}{c}{\(f_{\text{p,com,D}}\) (MPa)} & \multicolumn{3}{c}{\(\epsilon_{\text{p,pcom,D}}\) (10\({}^{-6}\))} & \multicolumn{3}{c}{\(\epsilon_{\text{c,pcom,D}}\) (GPa)} \\ \cline{3-10}  & & & _Mea._ & _Avg._ & _Std._ & _Mea._ & _Avg._ & _Std._ & _Mea._ & _Avg._ & _Std._ \\ \hline \multirow{8}{*}{Group 6} & \multirow{2}{*}{PR150-30-0.3} & 1 & 27.5 & & & 3425 & & 19.9 & & \\  & & 2 & 27.1 & 27.4 & 0.2 & 3802 & 3588 & 158 & 20.9 & 20.5 & 0.4 \\  & & 3 & 27.6 & & & 3537 & & & 20.8 & & \\  & & 1 & 29.1 & & & 3423 & & & 19.5 & & \\  & & 2 & 32.1 & 30.6 & 1.2 & 3579 & 3425 & 125 & 20.6 & 20.7 & 1.1 \\  & & 3 & 30.6 & & & 3274 & & & 22.1 & & \\  & & 1 & 31.9 & & 2291 & & & 19.8 & & \\  & & 2 & 35.0 & 33.4 & 1.3 & 2762 & 2538 & 193 & 20.6 & 20.5 & 0.5 \\  & & 3 & 33.2 & & 2562 & & & 21.0 & & \\  & & 1 & 31.5 & & & 2326 & & & 22.0 & & \\  & & 3 & 32.2 & 31.5 & 0.6 & 2357 & 2383 & 60 & 20.3 & 21.2 & 0.7 \\  & & 3 & 30.8 & & & 2467 & & & 21.4 & & \\  & & 1 & 27.1 & & & 1960 & & & 22.4 & & \\  & & 2 & 30.6 & 29.3 & 1.6 & 2248 & 2102 & 118 & 22.1 & 21.9 & 0.6 \\  & & 3 & 30.2 & & & 2099 & & & 21.1 & & \\ \hline \hline \end{tabular} Note. _Mea._, measured value; _Avg._, average value; _Std._, standard deviation.  
\end{table} 
Table 7: Experimental results of specimens in Group 6. 7. The combined peak strain generally increases with the replacement ratio. For a given replacement ratio, the peak strain of a prism is higher than that of the cylinder, and the difference increases with the replacement ratio. 8. When the characteristic ratio of the filler lumps is between 0.22 and 0.44, its effect on a prism's compressive strength is limited, but when the ratio reaches 0.55, an approximately 10% decrease in compressive strength is observed. 9. Larger lumps decrease the combined compressive strength of prisms more than cylinders, and of cylinders more than cubes. Any influence of the characteristic ratio on the combined elastic modulus and combined peak strain of prisms can normally be neglected. 10. As prism size increases, the combined compressive strength increases at first and then declines gradually. The combined peak strain generally decreases, but the change in the combined elastic modulus is very limited. [PERSON] and [PERSON] conceived and designed the experiments; [PERSON] performed the experiments; [PERSON], [PERSON], and [PERSON] analyzed the data and wrote the paper.