## 3 Test Results  
### Test for Compressive Strength  
The stress-strain curves obtained from the tests for compressive strength are plotted in Figure 5. The compressive strength and elastic modulus based on the stress-strain curves are summarized in Table 4. All the stresses in the strengthened specimen were calculated based on the cross-sectional area of the bare masonry prism for a consistent comparison. The average compressive strength and elastic modulus for the bare prisms were 11.9 and 1780 MPa, respectively. The compressive strength increased to 14.5 MPa (22% increase) for C-SF-30S strengthened on one side with a 30 mm ASFRM overlay, and 29.8 MPa (150% increase) for C-SF-30B strengthened on both sides with the same overlay thickness. The effect of the symmetrical strengthening scheme was more than double that of the added cross-sectional area. Similarly, increasing the thickness of the ASFRM overlay from 20 to 30 mm enhanced the compressive strength more effectively when overlays were applied to both sides of the prism. It can be presumed that the uneven distribution of normal stress in the cross section due to unsymmetrically plastered ASFRM resulted in low efficiency of strengthening, which will be addressed in derivation of design equations later. By adding glass fiber mesh to the ASFRM overlay, the compressive strength increased by 2.4 MPa for strengthening on one side but decreased by 7.3 MPa for strengthening on both sides; therefore, the glass fiber mesh did not yield a consistent positive effect. The overall tendency of improvement in the elastic modulus was similar to that in the compressive strength. Hence, it is unnecessary to use both the AS fiber and glass fiber mesh together.  
The damage states of the specimens after compressive failure are shown in Figure 6. Most specimens exhibited similar patterns of failure. First, cracks occurred on the lateral side of the masonry before reaching the maximum stress. Subsequently, additional cracks  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Average**} & \multicolumn{3}{c}{**Rate of Increase (\%)**} \\ \cline{2-6}
**Specimens** & **Peak** & **Compressive** & **\(E_{m}\) (MPa)** & **Compressive** & \(E_{m}\) \\  & **Load (kN)** & **Strength (MPa)** & **Compressive** & **Strength** & **Compressive** \\ \hline C-P & 204 & 11.9 & 1780 & - & - \\ C-SF-20S & 227 & 13.3 & 1980 & 11.8 & 11.2 \\ C-SF-30S & 248 & 14.5 & 2250 & 21.8 & 26.4 \\ C-SFM-30S & 290 & 16.9 & 2040 & 42 & 14.6 \\ C-SF-20B & 364 & 21.3 & 3950 & 79 & 121.9 \\ C-SF-30B & 511 & 29.8 & 3790 & 150 & 112.9 \\ C-SFM-30B & 385 & 22.5 & 2600 & 89.1 & 46.1 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Compressive strength test result.  
Figure 5: Compressive stress–strain curve: (**a**) C-SF-20S and C-SF-20B; (**b**) C-SF-30S and C-SF-30B; (**c**) C-SFM-30S and C-SFM-30B.  
occurred at the interface between the masonry layer and ASFRM overlay as the stress decreased. In addition, as shown in Figure 6b, for C-SF-30S, the ASFRM overlay did not crack, unlike the masonry, and the top of the prism strengthened on one side inclined significantly owing to the imbalance in strength and stiffness between the two layers.