# Compressive Behaviors of Prisms Made of Demolished Concrete Lumps and Fresh Concrete
## 2 Materials and Methods
### Testing Procedure  
To ensure that the top and bottom loading surfaces of the concrete specimen are parallel, the two surfaces should be smoothed with high-strength gypsum, cement, or sulphur [37]. In this study, all of the specimens were end-capped with high-strength gypsum, due to its properties of high strength and rapid hardening, and tested under axial compressive loading. In accordance with the standard test procedure specified in the ASTM C39 standard [38], the axial load was applied with a strain rate of 10 \(\times\) 10\({}^{-6}\)/s. An electro-hydraulic loading machine with a capacity of 10,000 kN (see Figure 5)  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Group** & **Specimen** & \begin{tabular}{c} **lateral Dimension \(D\)** \\ **(mm)** \\ \end{tabular} & \begin{tabular}{c} **Replacement** \\ **Ratio \(\eta\) (\%)** \\ \end{tabular} & \begin{tabular}{c} **Characteristic Size of** \\ **DCLs \(d\) (mm)** \\ \end{tabular} & \
\begin{tabular}{c} **Characteristic** \\ **Ratio \(\beta\) (\(d\) /D)** \\ \end{tabular} &
\begin{tabular}{c} **Number of** \\ **Specimens** \\ \end{tabular} \\ \hline \multirow{4}{*}{Group 4} & PR300 & 300 & 0 & — & — & 3 \\  & PR300-100-0.2 & 300 & 20 & 100 & 0.33 & 3 \\  & PR300-100-0.3 & 300 & 30 & 100 & 0.33 & 3 \\  & PR300-100-0.4 & 300 & 40 & 100 & 0.33 & 3 \\ \hline \multirow{4}{*}{Group 5} & PR300-67-0.3 & 300 & 30 & 67 & 0.22 & 3 \\  & PR300-100-0.3 & 300 & 30 & 100 & 0.33 & 3 \\  & PR300-133-0.3 & 300 & 30 & 133 & 0.44 & 3 \\  & PR300-167-0.3 & 300 & 30 & 167 & 0.55 & 3 \\ \hline \multirow{4}{*}{Group 6} & PR150-50-0.3 & 100 & 30 & 50 & 0.33 & 3 \\  & PR200-67-0.3 & 200 & 30 & 67 & 0.33 & 3 \\ \cline{1-1}  & PR300-100-0.3 & 300 & 30 & 100 & 0.33 & 3 \\ \cline{1-1}  & PR400-133-0.3 & 400 & 30 & 133 & 0.33 & 3 \\ \cline{1-1}  & PR500-167-0.3 & 500 & 30 & 167 & 0.33 & 3 \\ \hline \hline \end{tabular}
\end{table}
Table 2: _Cont._  
Figure 4: Concrete casting of specimens: (**a**) cylinders; (**b**) cubes; (**c**) prisms.  
was used in the compressive tests of the specimens with lateral dimensions of 200-500 mm. Another electro-hydraulic loading machine with a capacity of 5000 kN was used for the other specimens.  
Each cube was axially loaded to gain its compressive strength, and each cylinder or prism was axially loaded to obtain its compressive strength, elastic modulus, and strain at peak stress.  
To measure the axial deformations at two-fifths of the height of the cylinders and prisms, three (or four) linear variable differential transducers (LVDTs) with a calibrated range of \(\pm\)50 mm were installed on the side faces of the cylinders and prisms with lateral dimensions of 300-500 mm (see Figure 5b). Two LVDTs with a calibrated range of \(\pm\)5 mm were mounted on the other cylinders and prisms.  
To determine the specimens' elastic moduli, each specimen was first loaded three times to 40% of its estimated load-carrying capacity, and the average of the elastic moduli measured on the second and third loading cycles was taken as the specimen's elastic modulus. The elastic modulus related to the \(i^{th}\) (\(i\) = 2, 3) loading cycle was determined as \((\sigma_{2}-\sigma_{1})/(\epsilon_{2}-0.00005)\), where \(\sigma_{2}\) is the stress corresponding to 40% of the estimated compressive strength, \(\sigma_{1}\) is the stress corresponding to a strain of 0.005%, and \(\epsilon_{2}\) is the compressive strain at the stress level \(\sigma_{2}\)[39; 40] After that, the specimen was loaded to failure to ascertain its compressive strength and peak strain.  
The measured axial loads and deformations were recorded simultaneously by a data logger. Before the actual loading, each specimen was preloaded in order to lessen the impact on the test results of any looseness at the specimen's ends.