C16/20 vs C20/25

C20/25 and C16/20 are about equally stiff. Their densities are about the same. Per unit mass they are about equally stiff (11.85 and 12.26 MJ/kg). Strength: f_ck = 16 MPa for C16/20, f_ck = 20 MPa for C20/25.

C16/20 EN 1992-1-1 C20/25 EN 1992-1-1

Side by side

ratio = C20/25 / C16/20 · log scale

Property	C16/20	C20/25	Unit	Ratio
E Young's modulus	29	30	GPa	1.03×
G Shear modulus	12.08	12.5	GPa	1.03×
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	16	20	MPa	1.25×
f_ck,cube Characteristic cube strength	20	25	MPa	1.25×
f_cm Mean cylinder strength	24	28	MPa	1.17×
f_ctm Mean tensile strength	1.9	2.2	MPa	1.16×
f_ctk,0.05 Tensile strength, 5 % fractile	1.3	1.5	MPa	1.15×
f_ctk,0.95 Tensile strength, 95 % fractile	2.5	2.9	MPa	1.16×
ε_c1 Strain at peak stress	1.9	2	‰	1.05×
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	11.85	12.26	MJ/kg	1.03×
c₀ Bar wave speed √(E/ρ) · derived	3442	3501	m/s	1.02×
f/ρ Specific strength f/ρ · derived	6.538	8.172	kJ/kg	1.25×

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.