# Investigating the Poisson Ratio of 3D Printed Concrete
## 3 Results
### Porosity, Sphericity and Compactness  
The porosity characteristics of all the scanned specimens are given in Table 5. Clearly, the cast specimens, both CAST-CM and CAST-3 DPC, have lower porosity than their 3D printed counterparts at 1.61% and 1.84%, respectively. It is further evident that the pumping and extrusion process increases porosity, as CAST-3 DCP has a slightly higher porosity than CAST-CM. The highest porosity of 5.67% was obtained for the 3 DCPOIB specimen, extracted from the bottom of the printed element, as shown in Figure 2. The specimen extracted from the top of the printed element, 3 DCPOIT, has a porosity of 2.65%, less than half of its 3 DCPOIB counterpart. It is unknown at this stage what could have led to this discrepancy, but this warrants further investigation. However, since a large fraction of the porosity was located at the interlayer regions, it is clear that air entrapment occurs during the successive deposition (printing) process, resulting in the 3D printed specimens having higher porosity than their cast counterparts. Thus, the material deposition process has a larger influence on porosity than the pumping and extrusion process.  
The sphericity and compactness of all the scanned specimens are depicted in Figure 8. Both these measures follow identical patterns. The CAST-CM specimen has the highest sphericity and compactness, i.e., voids in this specimen are the most spherical/rounded, as is expected of conventionally cast concrete. Thereafter follows CAST-3 DCP, which indicates that the pumping and extrusion process does have an influence on void topology. The 3D printed specimens have the lowest sphericity and compactness, which indicates that the successive deposition (printing) process also influences void topology, more so than the pumping and extrusion process. Interestingly, the 3 DCPOIB specimen has the lowest sphericity and compactness, confirming a spatial variation in porosity and void topology exists over the height of a printed element. The authors postulate that a combination  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Groups** & **Count** & **Sum** & **Average** & **Variance** & & \\ \hline \hline \multicolumn{1}{c}{Cast-CM} & 5 & 0.92 & 0.18 & 0.000358 & & \\ \multicolumn{1}{c}{OI} & 5 & 1.03 & 0.21 & 0.000321 & & \\ \multicolumn{1}{c}{OIII} & 5 & 1.18 & 0.24 & 0.000523 & & \\ \hline \multicolumn{1}{c}{**Source of Variation**} & **SS** & **df** & **MS** & **F** & \(p\)**-value** & **F crit** \\ \hline \hline \multicolumn{1}{c}{Between groups} & 0.0069 & 2 & 0.00347 & 8.6661 & 0.0047 & 3.8853 \\ \multicolumn{1}{c}{Within groups} & 0.0048 & 12 & 0.00040 & & & \\ \multicolumn{1}{c}{Total} & 0.0118 & 14 & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 4: One-way ANOVA result of all tested groups.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Specimen** & **Specimen** & **Height** & **Diameter** & \(\delta_{\textbf{lat}}\) & \(\delta_{\textbf{long}}\) & \(\varepsilon_{\textbf{lat}}\) & \(\varepsilon_{\textbf{long}}\) & \(\gamma\) & \(\gamma\)avg \\ \multicolumn{1}{c}{**Configuration**} & **Number** & **mm** & **mm** & **mm** & **mm** & **mm/mm** & **mm/mm** & & \\ \hline \multirow{6}{*}{CAST-CM} & 1 & 59.61 & 29.81 & 0.01 & \(-\)0.1 & 0.000336 & \(-\)0.001678 & 0.2 & \\  & 2 & 59.67 & 29.84 & 0.01 & \(-\)0.13 & 0.000335 & \(-\)0.002179 & 0.15 & \\  & 3 & 59.65 & 29.95 & 0.01 & \(-\)0.11 & 0.000334 & \(-\)0.001844 & 0.18 & 0.18 \\  & 4 & 59.59 & 29.81 & 0.01 & \(-\)0.1 & 0.000335 & \(-\)0.001678 & 0.2 & \\  & 5 & 59.62 & 29.93 & 0.01 & \(-\)0.11 & 0.00034 & \(-\)0.001845 & 0.18 & \\ \hline \multirow{6}{*}{OI} & 1 & 59.01 & 29.76 & 0.01 & \(-\)0.11 & 0.000336 & \(-\)0.001864 & 0.18 & \\  & 2 & 59.04 & 29.77 & 0.01 & \(-\)0.10 & 0.000336 & \(-\)0.001609 & 0.21 & \\  & 3 & 59.00 & 30.10 & 0.01 & \(-\)0.09 & 0.000332 & \(-of overlay compaction [40] and bearing resistance capacity of freshly deposited concrete contribute toward this spatial variation.