C20/25 vs C45/55

C45/55 is 1.2 times as stiff as C20/25. Their densities are about the same. Per unit mass C45/55 is 1.2 times as stiff. Strength: f_ck = 20 MPa for C20/25, f_ck = 45 MPa for C45/55.

C20/25 EN 1992-1-1 C45/55 EN 1992-1-1

Side by side

ratio = C45/55 / C20/25 · log scale

Property	C20/25	C45/55	Unit	Ratio
E Young's modulus	30	36	GPa	1.2×
G Shear modulus	12.5	15	GPa	1.2×
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	20	45	MPa	2.25×
f_ck,cube Characteristic cube strength	25	55	MPa	2.2×
f_cm Mean cylinder strength	28	53	MPa	1.89×
f_ctm Mean tensile strength	2.2	3.8	MPa	1.73×
f_ctk,0.05 Tensile strength, 5 % fractile	1.5	2.7	MPa	1.8×
f_ctk,0.95 Tensile strength, 95 % fractile	2.9	4.9	MPa	1.69×
ε_c1 Strain at peak stress	2	2.4	‰	1.2×
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	12.26	14.71	MJ/kg	1.2×
c₀ Bar wave speed √(E/ρ) · derived	3501	3835	m/s	1.1×
f/ρ Specific strength f/ρ · derived	8.172	18.39	kJ/kg	2.25×

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.