Menu Selection 13) Hydrate a 3-D microstructure

The core of the VCCTL is Menu Selection 13 as it permits one to read in a starting microstructure, add some one-pixel particles (if needed), and perform hydration under user-specified curing conditions. The fill-in forms for doing this are shown in Figures 15 through 17. As with several other selections from the main menu, the VCCTL is currently set up to perform only one hydration at any specific time. Therefore, if the system is busy executing a hydration when another request is submitted, the user will be notified to resubmit their job at a later time.

To begin with, the user supplies a negative integer random number seed, and the names of the starting cement microstructure and particle image (typically the original image filename with the letter p in front of it) files to be used in the hydration. Then, they have the option of adding some one-pixel particles of various phases prior to the execution of the hydration. This table should be used to add the one-pixel (1 µm diameter) particles necessary to complete the cement PSD [1]. The exact number of one-pixel particles for each of the four cement phases and gypsum (or hemihydrate or anhydrite) can be determined from the volume counts (Menu Selection 9) for the final created 3-D microstructure along with the PSD established via Menu Selection 2, for example. Menu selection 2 will provide the total number of one-pixel particles to add, while Menu Selection 9 (along with the known phase compositon of the cement) will allow calculation of how this total number of one-pixel particles should be distributed to create a 3-D system that matches the desired overall phase composition of the cement [1]. A simple JavaScript routine to aid in this calculation is available as a help screen by clicking on the highlighted Number of one pixel particles to add:. Additionally, one-pixel particles of silica fume, an inert filler, or one phase of the user's choice can be added via this table.

The user then specifies the parameters that will control the hydration including:

1) the number of cycles of hydration to be executed,
• 2) the thermal curing conditions (isothermal, adiabatic, or temperature-defined),
• 3) the initial saturation curing conditions (saturated or sealed),
• 4) whether the conversion of primary C-S-H to pozzolanic C-S-H is prohibited or allowed (this selection is only relevant when pozzolanic materials such as silica fume or fly ash are present in the starting microstructure),
• 5) the frequencies in cycles to evaluate the water-filled porosity percolation, the percolation of total solids, and the individual particle hydration rates (these can be "disabled" by setting the frequencies to values larger than the requested number of cycles of hydration),
• 6) the initial curing temperature,
• 7) an estimate of the activation energy for cement hydration,
• 8) an estimate of the activation energy for the pozzolanic reactions,
• 9) the conversion factor to go from cycles of hydration to h of real time, and
• 10) the aggregate volume fraction in a concrete mixture (used for prediction of the adiabatic heat signature of a concrete -- can be set to 0.0 or left as is for cement paste systems).

Finally, the user once again supplies their e-mail address so that they may be notified when the hydration is completed. All of the parameters listed above are described in detail in Version 2.0 of the CEMHYD3D user's manual [1], and some of the entries in the form are highlighted in blue, indicating that supplemental help screens are directly available for viewing by clicking on the highlighted blue entry.

  

Figure 15: Form to hydrate a starting 3-D microstructure.

  

Figure 16: Form to hydrate a starting 3-D microstructure (continued).

  

Figure 17: Form to hydrate a starting 3-D microstructure (continued).

During the hydration, a number of output files are created by the CEMHYD3D program. These all utilize the starting microstructure filename as their root and add on appropriate extensions to indicate the results that each one contains. For example, if a file cemnew.img is hydrated for 4000 cycles of hydration at a starting temperature of 25 ºC and under isothermal and saturated conditions, the following output files will normally be created:

1) cemnew.img.4000.25.000 - microstructure image file after the hydration; the 4000 indicates the number of cycles of hydration, the 25 indicates the starting temperature, and the 000 indicates the selections for conversion of primary C-S-H to pozzolanic C-S-H (prohibited=0, allowed=1), thermal curing (isothermal=0, adiabatic=1, temperature-defined=2), and initial saturation (saturated=0, sealed=1),
• 2) cemnew.heat.4000.25.000 - output file containing a listing of the degree of hydration (both volume and mass bases), computed heat released, and computed gel-space ratio [11] vs. number of hydration cycles and computed real hydration time,
• 3) cemnew.adi.4000.25.000 - output file containing a listing of the system temperature vs. computed real hydration time,
• 4) cemnew.chs.4000.25.000 - output file containing a listing of the chemical shrinkage vs. number of hydration cycles and computed real hydration time,
• 5) cemnew.pha.4000.25.000 - output file containing a listing of the phase volume counts vs. number of hydration cycles,
• 6) cemnew.pps.4000.25.000 - output file containing a listing of the results for the examination of the percolation of the water-filled capillary porosity vs. cycles, computed hydration time, and degree of hydration,
• 7) cemnew.pts.4000.25.000 - output file containing a listing of the results for the examination of the percolation of the total solids vs. cycles, computed hydration time, and degree of hydration, and
• 8) cemnew.phr.4000.25.000 - output file containing a listing of the results for the hydration degree of individual particles after specific numbers of hydration cycles.

When Menu Selection 13 is executed, all of the user input parameters are echoed back in a form, along with the names of all of the output files that may be created by the CEMHYD3D program. However, normally, users don't need to concern themselves with the contents of these files, as they can instead use Menu Selection 17 to plot any specific property of interest for the systems that have been hydrated using Menu Selection 13.