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You can specify the characteristics of the concrete via the three windows shown in Figures 7.9, 7.10 and 7.11, or from the database list, by selecting a material. In that case Stadium fills all the parameters values automatically. If the user modifies some parameters of the selected material, the material name will not be an authentic database material name, and the current structural element material name will be changed to a “[Modified material – current structural element name]”.
Input Data window: Mixture proportions
Input Data window: Binder chemical Properties
Input Data window: Transport properties
The variables included in the material properties section are explained as follows:
• Reference temperature means the temperature measured in the laboratory where the material characterization testing is conducted.
• Water/binder means the water/binder ratio of the concrete mixture.
• Total Binder means the total amount of binder (cement and supplementary cementitious materials (SCMs), if any).
• Total Aggregates means the total amount of aggregates (fine and coarse) in the concrete mixture.
• Specific gravity is a measure of the density of the binder. It is typically 3.15 (3150kg/m3) for normal Portland cement and lower for mixtures with SCMs.
• Porosity means the total porosity of the material, expressed as the percentage of void volume in the material. This parameter can be evaluated using ASTM C642 Standard Test Method.
• Cement type means the type of Portland cement used in the concrete mixture. In this version, you can select between the five following cements: ASTM Type I or CSA Type 10, ASTM Type II or CSA Type 20, ASTM Type I/II, ASTM Type V or CSA Type 50. Pre-Blended binary and Pre-blended ternary cement. When performing simulations on concretes containing SCMs, the Type I (or Type 10) option should be selected.
• SCM means supplementary cementitious materials used in the concrete mixture. This version allows the selection between 4 types: Fly Ash type (C), Fly Ash type (F), Slag and Silica Fume. You can add no more than two SCMs in the same mixture.
• OH- diffusion coefficient: SIMCO Technologies Inc. has developed a procedure to evaluate the diffusion coefficient for each ionic species in the material based on the results of a migration test (see Experimental procedures). When the value for one species is known, values for the other species may be calculated. Accordingly, you enter only the OH- ion value. This value is directly provided by a companion software designed to analyze the migration test.
• Water diffusivity (A and B): Water diffusivity of cementitious materials is expressed as a nonlinear parameter: Dw = AeBw. It is evaluated from the results of a drying test (see Experimental procedures). The software required to evaluate A and B from the drying test results is currently under development at SIMCO Technologies Inc. Enter both A and B values. When a simulation is performed in saturated conditions, these values are not considered in the calculations, and you can enter any value, including zero, for both parameters.
• Initial hydration: enter the age of the concrete when first exposed to its environment. This feature was implemented to address precast materials, which may spend several weeks in storage before being exposed to the environment.
• Age of testing (days) means the age of the material when the previously entered transport properties were measured.
• Hydration parameters a and a: Transport properties tend to decrease with time as the cement’s hydration level increases. While this can usually be neglected for high water-to-cement ratios, it is an essential feature of high performance concrete durability. A hydration function incorporated in STADIUM® allows you to consider this phenomenon. The function, which multiplies the transport properties in the model, is given by:
• This function has the following properties: The parameter to represents the previously entered reference time. When t=to, H(t)=1. For large time values (t?8), the function H(t)=a. Accordingly, with a and a values lower than one, the hydration effect on concrete can be simulated. This is especially useful for materials prepared with fly ash. The parameter a represents the fraction of the transport properties values when hydration is complete compared to actual values. The parameter a is the rate at which the transport properties decrease over time. Typically, a is in the 0.2 – 0.8 range and a is in the 0.001 – 0.01 range. A helpful graph is displayed at the bottom of the Material Properties window, corresponding to H (t) for the selected parameters.
• Thermal conductivity means the thermal conductivity value of the material. Typical values for concrete are between 1 and 5 W/m2/K, according to reference. Simulation results have shown a weak sensitivity to this parameter.
• Specific heat means the specific heat value of the material. Typical values for concrete are between 800 and 1300 J/kg/K, according to Kim and al.1 Simulation results have shown a weak sensitivity to this parameter.
Web site: http://www.simcotechnologies.com/
