C12/15 vs C40/50

C40/50 is 1.3 times as stiff as C12/15. Their densities are about the same. Per unit mass C40/50 is 1.3 times as stiff. Strength: f_ck = 12 MPa for C12/15, f_ck = 40 MPa for C40/50.

C12/15 EN 1992-1-1 C40/50 EN 1992-1-1

Side by side

ratio = C40/50 / C12/15 · log scale

Property	C12/15	C40/50	Unit	Ratio
E Young's modulus	27	35	GPa	1.3×
G Shear modulus	11.25	14.58	GPa	1.3×
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	12	40	MPa	3.33×
f_ck,cube Characteristic cube strength	15	50	MPa	3.33×
f_cm Mean cylinder strength	20	48	MPa	2.4×
f_ctm Mean tensile strength	1.6	3.5	MPa	2.19×
f_ctk,0.05 Tensile strength, 5 % fractile	1.1	2.5	MPa	2.27×
f_ctk,0.95 Tensile strength, 95 % fractile	2	4.6	MPa	2.3×
ε_c1 Strain at peak stress	1.8	2.3	‰	1.28×
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	11.03	14.3	MJ/kg	1.3×
c₀ Bar wave speed √(E/ρ) · derived	3322	3782	m/s	1.14×
f/ρ Specific strength f/ρ · derived	4.903	16.34	kJ/kg	3.33×

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.