# Meta-Analysis of the Performance of Previous Concrete with Cement and Aggregate Replacements
## 5 Results and Discussion
### Combined Replacement of Cement and Aggregates in Pervious Concrete
**} & **Cement** & **Aggregate** & \multicolumn{4}{c}{**Mechanical**} & \multicolumn{2}{c}{**Hydraulic**} & **Durability** \\ \cline{3-10}  & **Replacement** & **Replacement** & **Compressive** & **Strength** & **Tensile** & **Elevral** & **Porosity** & **Permeability** & **Abrasion** \\  & **(Percentage)** & **(Percentage)** & **Density** & **Strength** & **Strength** & **Strength** & **Strength** & **Strength** & **Resistance** \\ \hline \multirow{2}{*}{[3]} & SG (100\%) & PN (5, 10, 15\%) & - & \(-\)2.0 & \(-\)2.6 & - & - & - & - & - \\  & SG (100\%) & PN (3, 6, 12\%) & - & 0.2 & 0.8 & - & - & - & - \\ \hline \multirow{4}{*}{[4]} & FA (10\%  
can be effectively utilized in combined replacement with other materials such as SF and SG, producing PC with improved mechanical and hydraulic performance. While similar properties were obtained with and without combined replacement, the performance of PC with combined replacement was more influenced by aggregate replacement than cement replacement. The combined replacement of cement and aggregates was analyzed using box and whisker plots to deduce the most practical combination of cement and aggregate replacements. The considered modes were OPC+NA, SCM+IWA, and SCM+RA, where SCM represents the cement replacement material. Figure 12a shows the influence of combined replacements on PC performance based on compressive strength. The respective medians of these three types of mixes for compressive strength were 9.9, 19.7, and 9.3 MPa. This shows that the combined replacement of SCM and IWA can positively affect the mechanical properties of PC, while incorporating SCM and RA in PC has a limited impact. Additionally, the interquartile ranges of SCM+IWA-PC and SCM+RA-PC were 14.3-26.9 MPa and 5.1-17.9 MPa, respectively, while that of the control PC was 6.0-23.0 MPa. The maximum and minimum whisker values were 4-39, 7-34, and 3.5-27 MPa for OPC+NA, SCM+IWA, and SCM+RA, respectively, signifying a reduction in the variability of the compressive strength with aggregate and cement replacement. Figure 11: Overall performance of combined replacements based on fixed effect. Figure 12: Variation in (**a**) Compressive strength, (**b**) Permeability, and (**c**) Porosity based on combined replacement (n = number of publications). Furthermore, the hydraulic performance of PC with the combined replacement of cement and aggregate was also assessed, as shown in Figure 12b,c. The medians for the permeability of PC mixes made with OPC+NA, SCM+IWA, and SCM+RA were 6.1, 5.0, and 6.2 mm/s, respectively, while their respective porosity medians were 21.5, 22.2, and 20.0%. From these values, similar hydraulic performance can be observed for all modes of replacements. Nevertheless, the minimum permeability was observed for SCM+IWA-PC, which may be due to its more compact structure, leading to high mechanical performance. The variability in outcomes for PC mixes made with OPC+NA, SCM+IWA, and SCM+RA was noted with respective interquartile ranges of 3.7-6.8, 2.5-9.0, and 5.6-8.4 mm/s and 19.9-23.4, 18.6-25.7, 17.5-24.6% for permeability and porosity. Similarly, respective whisker values for permeability and porosity were 0-21, 0-13, and 3.5-27 mm/s and 9.5-27.5, 14.5-29, and 10.5-28%. Based on the boxplot results, similar hydraulic performance of PC with and without combined replacement was observed. Thus, there is potential in producing PC with the combined replacement of cement and aggregates while exhibiting adequate hydraulic performance. In conclusion, viable mechanical and hydraulic performance was observed for SCM+IWA-PC. Meanwhile, the SCM+RA-PC mix had comparable properties to the control PC mix, rendering it a promising mix for future applications.