C20 vs C40

C40 is 1.5 times as stiff as C20. It is 1.2 times as dense. Per unit mass C40 is 1.2 times as stiff. Strength: f_m,k = 20 MPa for C20, f_m,k = 40 MPa for C40.

C20 EN 338:2016 C40 EN 338:2016

Side by side

ratio = C40 / C20 · log scale

Property	C20	C40	Unit	Ratio
E₁ Modulus, direction 1	9.5	14	GPa	1.47×
E₂ Modulus, direction 2	0.32	0.47	GPa	1.47×
E₃ Modulus, direction 3	0.32	0.47	GPa	1.47×
G₁₂ Shear modulus 1-2	0.59	0.88	GPa	1.49×
G₁₃ Shear modulus 1-3	0.59	0.88	GPa	1.49×
E₀,₀₅ Modulus parallel to grain, 5 % fractile	6.4	9.4	GPa	1.47×
ρ Density	400	480	kg/m³	1.2×
ρ_k Density, characteristic (5 % fractile)	330	400	kg/m³	1.21×
f_m,k Bending strength	20	40	MPa	2×
f_t,0,k Tension parallel to grain	11.5	26	MPa	2.26×
f_t,90,k Tension perpendicular to grain	0.4	0.4	MPa	1×
f_c,0,k Compression parallel to grain	19	27	MPa	1.42×
f_c,90,k Compression perpendicular to grain	2.3	2.8	MPa	1.22×
f_v,k Shear strength	3.6	4	MPa	1.11×
E/ρ Specific stiffness E/ρ · derived	23.75	29.17	MJ/kg	1.23×
c₀ Bar wave speed √(E/ρ) · derived	4873	5401	m/s	1.11×
f/ρ Specific strength f/ρ · derived	50	83.33	kJ/kg	1.67×

Values at the first thickness band or product form of each material (EN 338:2016; EN 338:2016). A minimum and a characteristic value are not the same kind of number — read the ratio as a guide. Each material's page lists every band and every source.