a, b	Parameters related to ascending and descending portions in the model
$E_{cm}$	Secant modulus at 0.4$f_c^{\prime }$
$E_0$	Secant modulus at $f_c^{\prime }$
$E_c$	Elastic modulus
$f_c$	Compressive stress
$f_c^{\prime }$	Peak compressive stress
$f_{max0}$	Peak compressive stress of normal concrete
$f_{28}$	Compressive strength after 28 days
$k$	The parameter in a model by EU code [48] and model by Belen et al. [38]
$k_e$	A coefficient used in proposed model
$m_1$	The parameters in the model by Xiao et al. [54]
m, n, p, q	The constant parameters in the model by Xiao et al. [54]
$r$	Volume replacement rate
$t$	Curing time
$\mu , \nu$	The constant parameters in the model by Xiao et al. [54]
${\alpha }_c$	Shape parameter ${\alpha }_c$ used in Xiao et al. [54]
${\alpha }_c^{rec} {\beta }_c^{rec}$	The adjustment factors in the model by Belen et al. [38]
$\beta$ $, {\beta }_m$	A concrete material parameter
${\epsilon }_c$	Axial compressive strain
${\epsilon }_c^{\prime }$	Peak axial strain at $f_c^{\prime }$
${\epsilon }_{cu}$	Ultimate axial strain
${\rho }_c$	The parameters in the model by Xiao et al. [54]
${\phi }_{cm}^{rec}$	The adjustment in the model by Belen et al. [38]