C25/30 vs C40/50

C40/50 is 1.1 times as stiff as C25/30. Their densities are about the same. Per unit mass C40/50 is 1.1 times as stiff. Strength: f_ck = 25 MPa for C25/30, f_ck = 40 MPa for C40/50.

C25/30 EN 1992-1-1 C40/50 EN 1992-1-1

Side by side

ratio = C40/50 / C25/30 · log scale

Property	C25/30	C40/50	Unit	Ratio
E Young's modulus	31	35	GPa	1.13×
G Shear modulus	12.92	14.58	GPa	1.13×
ν Poisson's ratio	0.2	0.2	–	1×
ρ Density	2447	2447	kg/m³	1×
γ Weight density	24	24	kN/m³	1×
α Coefficient of thermal expansion	10	10	10⁻⁶/K	1×
f_ck Characteristic cylinder strength	25	40	MPa	1.6×
f_ck,cube Characteristic cube strength	30	50	MPa	1.67×
f_cm Mean cylinder strength	33	48	MPa	1.45×
f_ctm Mean tensile strength	2.6	3.5	MPa	1.35×
f_ctk,0.05 Tensile strength, 5 % fractile	1.8	2.5	MPa	1.39×
f_ctk,0.95 Tensile strength, 95 % fractile	3.3	4.6	MPa	1.39×
ε_c1 Strain at peak stress	2.1	2.3	‰	1.1×
ε_cu1 Ultimate strain	3.5	3.5	‰	1×
ε_c2 Strain at peak, parabola–rectangle	2	2	‰	1×
ε_cu2 Ultimate strain, parabola–rectangle	3.5	3.5	‰	1×
n Exponent, parabola–rectangle	2	2	–	1×
ε_c3 Strain at peak, bilinear	1.75	1.75	‰	1×
ε_cu3 Ultimate strain, bilinear	3.5	3.5	‰	1×
E/ρ Specific stiffness E/ρ · derived	12.67	14.3	MJ/kg	1.13×
c₀ Bar wave speed √(E/ρ) · derived	3559	3782	m/s	1.06×
f/ρ Specific strength f/ρ · derived	10.22	16.34	kJ/kg	1.6×

Values at the first thickness band or product form of each material (EN 1992-1-1; EN 1992-1-1). 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.