## 3 Results and Discussion  
### Mechanical Properties Test  
#### 3.1.1 Compression Test  
Figure 7 and Table 4 show averaged curves and compressive stresses at 10% strain from the uni-axial compression test of EPS, with densities of 22 and 23 kg/m\({}^{3}\). In this paper, it was universally applied that if there were two values in one cell, they represented results obtained from specimens cut with a hot wire and with a table saw, respectively. Values in parentheses always represent standard deviation based on a sample.  
EPS23 exhibited a higher compressive strength and initial modulus than EPS22. Compared to EPS22, EPS23 was 8.2% stronger in compressive strength if cutting with a hot wire and 7.4% stronger if cutting with a table saw. Initial moduli were 14.9% higher and 10.3% higher for cutting with a hot wire and with a table saw, respectively. However, all test groups observed the second tangent modulus to be parallel.  
Comparing EPS22 with EPS22*, the compressive strength curves were observed to overlap in the plateau region but the initial modulus increased with specimen thickness, both in cases of cutting with a hot wire and with a table saw. The initial moduli of EPS22 were 22.2% higher and 26.8% higher than EPS22* for cutting with a hot wire and with a table saw, respectively. This indicated that the thickness of specimens affected the initial modulus and did not influence tangent modulus and compressive strength.  
Specimens cut with a hot wire exhibited higher compressive strength than cutting with a table saw in all test groups. For EPS23, the compressive strength of specimens cut with a hot wire was 2.6% higher and, for EPS22 and EPS22*, these values were 1.8% and 1.9%, respectively. Although the validity of the correlation below was likely to be compromised because of inadequate data source, the compressive strength increment of the specimen due to cutting with a hot wire in correlation to the density was put forward here for future reference.  
\[\Delta\sigma/\sigma\times 100\%=0.8\rho-15.8, \tag{1}\]  
where \(\Delta\sigma\) refers to the increment of compressive strength \(\sigma\) in kPa and \(\rho\) is the density of EPS in kg/m\({}^{3}\).  
Based on the observation of standard deviation values and error bars from Table 4, the results of specimens cut with a hot wire were more variable than those cut with a table saw. This indicated that the methods of preparing specimens affected the compressive strength of EPS to some extent. If specimens were cut with a hot wire, the compressive strength was roughly around 2% higher than using a table saw. Apart from compressive strength, the initial moduli appeared close to each other in the two methods of preparation, and the major difference was that specimens cut with a table saw yielded earlier than those with a hot wire. Nevertheless, there appeared to be a minor influence on Young's modulus when a different method of preparation was applied.  
In previous studies, the compressive strength of EPS was most frequently tested in material property investigation. The comparison of this study's results with experimental results reported in the literature for the last 10 years is listed in Table 5. Results from adjacent densities (19, 20, 22 and 25 kg/m\({}^{3}\)) were gathered hereinafter. According to ASTM D6817, compressive resistance at 10% strain for EPS19 and EPS22 was required to be at least 110 kPa and 135 kPa, respectively. The data from the literature, including this study, generally varied around these values. That the compressive strength from this study appears to be slightly higher than the others could be a result of higher measured density.