# Meta-Analysis of the Performance of Previous Concrete with Cement and Aggregate Replacements
## 5 Results and Discussion
### Cement Replacement in Pervious Concrete
#### 5.2.2 Performance Evaluation  
Table 1 summarizes the type of replacement material, percentage of replacement, and effect size of PC performance. The results show that PC with partial and complete cement replacement generally has comparable mechanical properties compared to OPC-based PC. With 14 of the 21 effect sizes for bulk density being positive, it can be noted that the bulk density of PC made with cement replacement is dependent on the replacement material and percentage. PC made with partial cement replacement by SF, BL, NC, FA, MK, STF, and MF and with complete replacement by SG had a higher bulk density than counterparts made with cement only. It seems that these materials densified the matrix and reduced the porosity, as evidenced by their respective positive and negative bulk density and porosity effect sizes. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Ref.**} & \multirow{2}{*}{**Type**} & \multirow{2}{*}{**Percentage**} & \multicolumn{3}{c}{**Mechanical Properties**} & \multicolumn{3}{c}{**Hydraulic Properties**} & \multicolumn{3}{c}{**Durability**} \\ \cline{3-10}  & & & **Bulk Density** & **Strength** & **Tensile Strength** & **Flexural Strength** & **Porosity** & **Permeability** & **Abrasion Resistance** \\ \hline \hline \multirow{2}{*}{[4]} & CA+RHA & 15\% + 15\% & * & \(-\)0.6 & - & - & 0.1 & \(-\)0.1 & - \\ \hline \hline \multirow{2}{*}{[8]} & POFA & 10, 20, 30, 40\% & \(-\)1.3 & \(-\)1.8 & \(-\)1.8 & - & 1.7 & 1.8 & 1.5 \\ \hline \multirow{2}{*}{[9]} & FA+SG & 15\% + 25\% & - & \(-\)1.1 & \(-\)14 & \(-\)19 & 12.8 & 2.5 & - \\ \hline \multirow{5}{*}{[10]} & SF+NC (2\% STF) & 10\% + 1\% & - & 14 & - & 4.9 & \(-\)8.2 & \(-\)3.7 & - \\  & SF+NC & 10\% + 2\% & - & 25.2 & - & 23.1 & \(-\)8.1 & \(-\)10.5 & - \\  & SF+NC & 10\% + 3\% & - & 49.8 & - & 10.4 & \(-\)4.3 & \(-\)8.2 & - \\  & SF+NC (2\%WPF) & 10\% + 1\% & 6.5 & 1.2 & 1.8 & 2.1 & \(-\)1.4 & \(-\)1.7 & - \\  & SF+NC & 10\% + 2\% & 4.9 & 2.0 & 1.5 & 2.3 & \(-\)1.7 & \(-\)1.2 & - \\  & SF+NC & 10\% + 3\% & 5.9 & 2.2 & 2.6 & 1.7 & \(-\)1.6 & \(-\)1.5 & - \\ \hline \multirow{5}{*}{[17]} & SF & 5, 10\% & 3.0 & 4.4 & 1.5 & 2.3 & \(-\)3.5 & \(-\)3.5 & \(-\)9.0 \\  & BL & 10, 20\% & 6.0 & 1.9 & 1.0 & 1.2 & \(-\)6.7 & \(-\)2.6 & \(-\)21.0 \\ \cline{1-1}  & RF & 1.5, 3\% & \(-\)3.0 & \(-\)1.3 & \(-\)3.0 & \(-\)3.0 & 3.4 & 9.0 & - \\ \cline{1-1}  & CR & 5, 10\% & \(-\)3.0 & \(-\)2.5 & \(-\)4.3 & \(-\)3.4 & 2.0 & 5.0 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Effect size for PC performance based on cement replacement. Furthermore, PC incorporating different SCMs and fibers, including FA, SF, BC, STF, WPF, and SCBA, yielded 24, 16, and 12 positive effect sizes out of 36, 25, and 16 effect sizes for compressive, tensile, and flexural strengths, respectively, indicating a general improvement in mechanical performance with cement replacement. This is mainly due to the pozzolanic reactivity of the replaced materials, which enhanced the properties of the PC [10; 17; 21; 25; 27; 35; 36; 39; 43; 44]. However, the replacement of cement with other SCMs such as PR and POFA resulted in negative effect sizes, indicating inferior strengths with cement replacement. This may be due to the lower pozzolanic reactivity of these materials coupled with higher replacement percentages, inducing a filling effect with less binder. Alternatively, out of the 32 and 31 respective effect sizes for porosity and permeability, 16 positive effect sizes were obtained for each hydraulic property in PC made with POFA, RF, CR, SG, PR, PU, and SCBA [8; 45]. It seems that the finer particle size of the replacement materials and the higher degree of reaction in PC with cement replacement may have densified the concrete skeleton and reduced the hydraulic properties [46; 47]. Furthermore, PC made with cement was generally more abrasion resistant than that made with partial or complete cement replacement, as 7 of the 8 effect sizes were negative.