Input parameters

The parameters can be divided into three main categories:

1. Geometry: Dimensions of modeled structural elements. Since most cases can be simplified to 1D, the characteristic length of structural elements must be provided (e.g. deck thickness). As STADIUM® is based on the finite element method, information on the discretization of the spatial domain is also needed.
2. Exposure Conditions (Environment): Temperature, relative humidity, composition of solutions in contact with the structure. In the case of seawater, its composition is commonly expressed as the salinity which must be converted into individual species concentration. For example, a 32 ppt seawater salinity corresponds to (all values in mmol/L): 426.1 Na⁺, 9.0 K⁺, 25.6 SO₄^2–, 9.3 Ca²⁺, 48.6 Mg²⁺, 3.8 HCO₃^–, and 495.8 Cl^–. Depending on the type of exposure, all these parameters can be time-dependent.
3. Material Properties: They can be divided into two categories. Parameters are associated with 1) transport equations (transport properties), while others are related to 2) the chemical module. The transport properties are summarized in Table 1. Parameters needed by the chemical module are presented in Table 2. All other parameters not found in these tables are either physical constants that can be found in textbooks or parameters for which a relationship was found in scientific literature and implemented in the model (e.g. relative permeability k_rl and saturation vapor pressure p^s_v).

Table 1 – Transport Module Parameters

Parameter	Symbols	Test Method	Note
Volume of permeable voids (porosity)	?	ASTM C642	Also provides mixture density.
Diffusion coefficient	Di	Migration test	Modified version of ASTM C1202 (RCPT). The test consists in accelerating ionic transport by applying 20 V to a saturated sample. Electrical currents are measured over 2 weeks and analyzed with the STADIUM® LAB module. The test provides the diffusion coefficient of each species in the material (e.g. Na+, K+, Cl–). It also provides intrinsic tortuosity ?s.
Intrinsic permeability	ks	ASTM C1792	The mass loss data measured over 30 days during the concrete sample drying at 50% RH is analyzed with the  STADIUM® LAB module to provide the permeability.
Moisture isotherm (water retention function, saturation curve)	?, ?	ASTM C1792 (modified)	The drying test is performed on thin (10mm) samples over 30 days at 50% RH. A model is then used to estimate the equilibrium water content at 50% RH and evaluate ? and ?. The estimation of the equilibrium water content relies on SIMCO’s material database.
Aging function	a, ?	Migration test	Migration tests performed at different curing durations can be used. If this is not possible, the aging function can be estimated using information found in SIMCO’s concrete mixture database. Mixtures were tested over a two-year period, which allowed estimating the aging function.

Table 2 – Initial Chemical Composition of the Hydrated Cement Paste

Parameter	Symbols	Test method	Note
Initial solid phase content	Sm	–	The initial content in portlandite, C-S-H, AFm, AFt, and other phases initially present in the hydrated cement paste is estimated on the basis of the mixture proportions and cement chemical analysis.
Initial pore solution	Ci	Pore solution extraction	Although it is possible to physically extract solutions from concrete samples to measure this parameter, it is expensive and inaccurate. Models based on mixture proportions and cement chemical analysis are used to estimate the initial concentration in Na+, K+, OH–, Cl–, …

Technical Information