Concrete Grades to Eurocodes
An extract from Table 3.1 of BS EN 1992-1-1 is shown below. Eurocode practise is to use Cylinder Strength for concrete, instead of Cube Strength which was used in previous British Standards. Cylinders are tests using a sample with an aspect ratio of 2:1, instead of the cube same of aspect ratio 1:1. Therefore, for the same type of concrete a cube sample will suggest a higher concrete strength, this is reflected in the below table.
| C25/30 | C30/37 | C35/45 | C40/50 | C45/55 | C50/60 | C55/67 | C60/75 | C70/85 | Equation | |
|---|---|---|---|---|---|---|---|---|---|---|
| \(f_{ck}\) | 25 | 30 | 35 | 40 | 45 | 50 | 55 | 60 | 70 | - |
| \(f_{ck,cube} \) | 30 | 37 | 45 | 50 | 55 | 60 | 67 | 75 | 85 | - |
| \(f_{cm} \) | 33 | 38 | 43 | 48 | 53 | 58 | 63 | 68 | 78 | \(f_{cm} = f_{ck} +8 \text{ MPa}\) |
| \(f_{ctm} \) | 2.6 | 2.9 | 3.2 | 3.5 | 3.8 | 4.1 | 4.2 | 4.4 | 4.6 | \(f_{ctm} = 0.3 \times f_{ck}^{2/3} \leq C50/60\) \(f_{ctm} = 2.12 \ln (1+(f_{ck}/10)) > C50/60\) |
| \(f_{ctk,0.05} \) | 1.8 | 2 | 2.2 | 2.5 | 2.7 | 2.9 | 3 | 3.1 | 3.2 | \(f_{ctk,0.05} = 0.7 \times f_{ctm} { MPa}\) |
| \(f_{ctk,0.95}\) | 3.3 | 3.8 | 4.2 | 4.6 | 4.9 | 5.3 | 5.5 | 5.7 | 6 | \(f_{ctk,0.95} = 1.3 \times f_{ctm} { MPa}\) |
| \(E_{cm}\) | 31000 | 33000 | 34000 | 35000 | 36000 | 37000 | 38000 | 39000 | 41000 | \(E_{cm} = 22,000 [ f_{cm}/10]^{0.3}\text{ } f_{cm} \text{ in MPa}\) |
| \(\varepsilon_{c1} (^0\!\!/\!_{00})\) | 2.1 | 2.2 | 2.25 | 2.3 | 2.4 | 2.45 | 2.5 | 2.6 | 2.7 | \(\varepsilon_{c1} (^0\!\!/\!_{00}) = 0.7 f_{cm}^{0.31}\leq 2.8\) |
| \(\varepsilon_{cu1} (^0\!\!/\!_{00})\) | 3.5 | 3.5 | 3.5 | 3.5 | 3.5 | 3.5 | 3.2 | 3 | 2.8 | \(\varepsilon_{cu1} (^0\!\!/\!_{00}) = 2.8+27[(98-f_{cm})/100]^4 > C50/60\) |
| \(\varepsilon_{c2} (^0\!\!/\!_{00})\) | 2 | 2 | 2 | 2 | 2 | 2 | 2.2 | 2.3 | 2.4 | \(\varepsilon_{c2} (^0\!\!/\!_{00}) = 2.0+0.085(f_{ck}-50)^{0.53} > C50/60\) |
| \(\varepsilon_{cu2} (^0\!\!/\!_{00})\) | 3.5 | 3.5 | 3.5 | 3.5 | 3.5 | 3.5 | 3.1 | 2.9 | 2.7 | \(\varepsilon_{cu2} (^0\!\!/\!_{00}) = 2.6+35[(90-f_{ck})/100]^4 > C50/60\) |
| \(n\) | 2 | 2 | 2 | 2 | 2 | 2 | 1.75 | 1.6 | 1.45 | \( n = 1.4+23.4[(90-f_{ck})/100]^4 > C50/60\) |
| \(\varepsilon_{c3} (^0\!\!/\!_{00})\) | 1.75 | 1.75 | 1.75 | 1.75 | 1.75 | 1.75 | 1.8 | 1.9 | 2 | \( \varepsilon_{c3} (^0\!\!/\!_{00}) = 1.75+0.55[(f_{ck}-50)/40] > C50/60\) |
| \(\varepsilon_{cu3} (^0\!\!/\!_{00})\) | 3.5 | 3.5 | 3.5 | 3.5 | 3.5 | 3.5 | 3.1 | 2.9 | 2.7 | \(\varepsilon_{cu3} (^0\!\!/\!_{00}) = 2.6+35[(90-f_{ck})/100]^4 > C50/60\) |