## 3 Results
### Physical Properties
#### 3.3.2 Open Porosity  
The open porosity (P\({}_{\text{o}}\)) data in Table 8 show greater pore volume in all the mixes containing GRC and MRA than in the reference NAC. This was attributed to two factors: the larger w/b\({}_{\text{eff}}\) ratio in the new cementitious matrices associated with the greater water demand in the new binders (RB\({}_{10}\) and  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**NA mix**} & \multicolumn{3}{c}{**MRA mix**} \\ \cline{2-7}
**Parameter/Differential** & **NAC** & **N10/0** & **N25/0** & **R0/50** & **R10/50** & **R25/50** \\ \hline \(\rho_{dy}\) (kg/m\({}^{3}\)) & 2290 \(\pm\) 35 & 2227 \(\pm\) 20 & 2158 \(\pm\) 25 & 2101 \(\pm\) 40 & 2052 \(\pm\) 38 & 1990 \(\pm\) 42 \\ \(\Delta\) with GRC (\%) & - & -2.8 & -5.8 & - & -2.3 & -5.3 \\ \(\Delta\) with MRA (\%) & & & & -8.3 & -7.9 & -7.8 \\ \(\Delta\) with GRC (\%)\(\times\) MRA (\%) & & & & -10.4 & -13.1 \\ \(\text{P}_{\text{o}}\) (volv) & 12.1 \(\pm\) 0.2 & 12.7 \(\pm\) 0.3 & 13.7 \(\pm\) 0.3 & 15.2 \(\pm\) 0.4 & 15.9 \(\pm\) 0.5 & 16.9 \(\pm\) 0.3 \\ \(\Delta\) with GRC (\%) & - & 5.0 & 13.2 & - & 4.6 & 11.2 \\ \(\Delta\) with MRA (\%) & & & & 26.5 & 25.2 & 23.4 \\ \(\Delta\) with GRC (\%)\(\times\) MRA (\%) & & & & 31.4 & 39.7 \\ \(\text{EC}\) (10\({}^{3}\)) \(\Omega\)m\({}^{-1}\)) & 8.8 \(\pm\) 0.5 & 9.5 \(\pm\) 0.3 & 10.6 \(\pm\) 0.3 & 9.9 \(\pm\) 0.3 & 102.4 \(\pm\) 0.2 & 11.1 \(\pm\) 0.4 \\ \(\Delta\) with GRC (\%) & - & -7.1 & -16.8 & – & -3.0 & -10.9 \\ \(\Delta\) with MRA (\%) & & & & -10.6 & -6.7 & -4.3 \\ \(\Delta\) with GRC (\%)\(\times\) MRA (\%) & & & & -13.3 & -20.4 \\ \hline \hline \end{tabular}  
* Notes: \(\Delta\) with GRC (\%) compares NAC to N10/0 and to N25/0 in mixes with NA; and R0/50 to R10/50 and to R25/50 in mixes with MRA; \(\Delta\) with MRA (%) compares NAC to R0/50, N10/0 to R10/50 and N25/0 to N25/50; \(\Delta\) with GRC \(\times\) MRA (%); compares NAC to R10/50 and to R25/50.  
\end{table}
Table 8: Physical properties of the concrete mixes.  
RB\({}_{25}\)); and higher water absorption MRA (9.1%) than NA (1.3%) (higher open porosity) primarily due to the presence of bound mortar and fired clay-based material in MRA [49]. Those results are consistent with earlier studies on concrete batched with up to 100% MRA [50], up to 100% RCA [51] and concrete with up to 100% RCA fine and 100% RCA coarse aggregate [52].  
The use of GRC raised P\({}_{\rm o}\) by 5.0% in N10/0 and 13.2% in N25/0 relative to NAC and by 4.6% in R10/50 and 11.2% in R25/50 relative to R0/50, an indication that the joint use of CDW as additions and aggregates had no adverse effect on open porosity. As Figure 4b shows, a direct linear relationship (R\({}^{2}\)\(\geq\) 0.997) was observed between open porosity and GRC replacement ratio in all the mixes, whether containing NA or MRA, where it was added. The vertical distance between the two trend lines depicts the impact of replacing 50% NA with MRA, which induced a maximum rise in the mean P\({}_{\rm o}\) of up to 25% in the MRA (R0/50, R10/50, R25/50) relative to the NA mixes (NAC, N10/0, N25/0).  
All the P\({}_{\rm o}\) values lay within the 12.5% to 17% range reported in the literature for concrete made with 50% MRA [52; 53; 54] and concrete made jointly with 30% ground granulated blast furnace slag and 50% RCA [55].