# Dimensional Stability of SBR-Modified Cementitious Mixtures for Use in 3D Additive Construction
## 3 Materials and Specim Preparation
### Mixture Proportions  
Among the many constituents used in this study, the mixture proportions of materials other than SBR were determined through the process of trial and error. SBR latex was added according to the SBR/cement ratios (i.e., 0, 0.05, 0.10, 0.15, and 0.20). The amount of water used was determined based on a water/cement ratio that could maintain a flow of 70% \(\pm\) 1% for each mixture because the flow of 70% \(\pm\) 1% was determined by [PERSON] et al. (2013) as the optimal flow of SBR-modified cementitious mixtures to apply 3 DAC. Table 8 shows the mixture proportions identified for these conditions.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Specific Gravity** & **DH** & **Alkali Content** & **Chloride Content** \\
**(20 \({}^{\circ}\)C)** & **pH** & **(kg/m\({}^{3}\))** & **(kg/m\({}^{3}\))** \\ \hline \(1.05\pm 0.05\) & \(5.0\pm 2.0\) & 0.03 & \(0.03\times 10^{-3}\) \\ \hline \hline \end{tabular}
\end{table}
Table 6: Properties of superplasticizer.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Total Solids** & **pH** & **Viscosity** & **Surface** & **Specific Gravity** & **Minimum** \\
**(\%)** & **pH** & **(mPa-s)** & **(dynes/cm)** & **(20\({}^{\circ}\)C)** & **Temp. (\({}^{\circ}\)C)** \\ \hline
47–50 & 9.9–10.5 & 40 & 30–35 & \(1.01\pm 0.01\) & \(<\)4 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Properties of SBR latex.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**SiO\({}_{2}\)** & **H\({}_{2}\)O** & **Loss on** & **Bulk Density-** & **Bulk Density-** \\
**(\%)** & **(\%)** & **Ignition (\%)** & **Undensified (kg/m\({}^{3}\))** & **Densified (kg/m\({}^{3}\))** & **(cm\({}^{2}\)/g)** \\ \hline
96.7 & \(<\)1.0 & \(<\)3.0 & 200–350 & 600–700 & 157,700 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Properties of silica fume.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Density** & **Chemical Composition (\%)** & **Specific Surface** \\ \cline{2-5}
**(g/cm\({}^{3}\))** & **MgO** & **SO\({}_{3}\)** & **Loss on Ignition** & **(cm\({}^{2}\)/g)** \\ \hline
3.14 & 2.91 & 2.41 & 2.16 & 3630 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Properties of ordinary Portland cement.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Appearance** & **pH (Solution)** & **Bulk Density** & **Moisture Content** & **Particle Size** \\
**(kg/m\({}^{3}\))** & **(\%)** & **(\%)** & **(0.074 mm, \%)** \\ \hline White powder & 8.0–10.0 & 430 & \(\leq\)12 & \(\geq\)95 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Properties of viscosity modifying agent.  
The flow of 70% \(\pm\) 1% is optimal, as determined through experiments regarding the four properties of the fresh SBR-modified cementitious mixtures required for 3 DAC: flowability, extrudability, buildability, and open time. It is of note that the optimal flow of 70% \(\pm\) 1% is quite small considering the standard flow of 110% \(\pm\) 5% defined in ASTM C109/C109M-02: Testing Method for Compressive Strength of Hydraulic Cement Mortar [14], used when producing cementitious mortar specimens for compressive strength testing.