 |
Menu Selection 3 is used to create an initial 3-D microstructure consisting of cement (gypsum, and filler) particles in water. For this form, the user will find several entries that are highlighted (in blue). Clicking on any of these will direct the user to supplementary help information screens. Often, the articles referenced in these help screens are directly accessible online as part of the Electronic Monograph: Modelling and Measuring the Structure and Properties of Cement-Based Materials (available at http://ciks.cbt.nist.gov/monograph) [8].
The form for Menu Selection 3 is shown in Figures 6 through 8. The user must provide a negative integer random number seed, the thickness of the single aggregate particle (slab) placed in the middle of the 3-D microstructure (if any), and to what degree (if any) the particles are to be dispersed or flocculated. In addition, they must supply information on the calcium sulfate (gypsum) content and form (dihydrate, hemihydrate, and anhydrite). Here, the user specifies first the total volume fraction of randomly distributed calcium sulfate and then the fractions of this total that are to be assigned as hemihydrate and anhydrite, respectively (with the remainder being distributed as the dihydrate form of calcium sulfate). The specific PSD to be used in creating the 3-D microstructure must next be specified. For the PSD, the user has the choice of directly specifying the number and phase of each size particle via the table in Figure 7, or reading in this information from a PSD datafile created using Menu Selection 2, as discussed above. Finally, the user needs to specify a filename in which to store the created microstructure and their e-mail address. Once the execution of the genpartnew program is complete, an e-mail notification will be sent to the user at the specified e-mail address. If the genpartnew program is unable to place the requested numbers of particles, the user will be notified of this by e-mail as well, and instructed to modify their inputs and resubmit the form.
Calcium sulfate (gypsum) additions can be handled in one of two ways during the microstructure creation step. If only the composite PSD of the cement and gypsum is known, a specific fraction of the cement particles can be randomly assigned to be gypsum. Conversely, if both the PSDs of the cement and gypsum are available separately, the PSD table can be used to provide the specific numbers of each size particle which are to be cement and gypsum, respectively. In this case, the "Total randomly distributed calcium sulfate fraction" in Figure 6 would be specified to be 0.0. The same specifications can be done with cement and fly ash particles, or cement and inert filler particles. While the user can change the individual particle diameter entries in the table shown in Figure 7, they should be sure that the entries are always in descending order, starting with the largest diameter particles. This is to ensure that during random particle placement, there is the best chance that there is some open space available for the last (smallest) particles to be placed. If the smallest particles are randomly located first, there may not remain any empty spaces of adequate size to fit the (last) larger ones.
In addition, it should be noted that only particles 3 pixels (µm) in diameter and larger are normally added during the execution of Menu Selection 3. The smaller 1-pixel diameter particles of the various cement clinker phases, gypsum, silica fume, etc. should instead be specified just prior to the hydration using a fill-in table with Menu Selection 13 (see Figure 15). This is done to allow the optional flocculation of the 3 pixel diameter and larger particles during the creation of the 3-D particle microstructure image. Because the 1-pixel particles are generally quite large in number, their inclusion in the flocculation algorithm would result in dramatic increases in the memory and time requirements of the 3-D microstructure creation program.
Input PSD in table provided below
Read PSD from datafile (include extension in name:) part001.psd
Click on boxes under Phase to select
(defaults for cement will give a w/c of about 0.4)
| Diameter (µm) | Number of Particles | Phase |
| 41 | 0 | cement (C3S) |
| 41 | 0 | fly ash |
| 37 | 0 | cement (C3S) |
| 37 | 0 | fly ash |
| 35 | 1 | cement (C3S) |
| 35 | 0 | fly ash |
| 33 | 0 | cement (C3S) |
| 33 | 0 | fly ash |
| 31 | 1 | cement (C3S) |
| 31 | 0 | fly ash |
| 29 | 1 | cement (C3S) |
| 29 | 0 | fly ash |
| 27 | 1 | cement (C3S) |
| 27 | 0 | fly ash |
| 25 | 1 | cement (C3S) |
| 25 | 0 | fly ash |
| 23 | 2 | cement (C3S) |
| 23 | 0 | fly ash |
| 21 | 3 | cement (C3S) |
| 21 | 0 | fly ash |
| 19 | 4 | cement (C3S) |
| 19 | 0 | fly ash |
| 17 | 7 | cement (C3S) |
| 17 | 0 | fly ash |
| 15 | 10 | cement (C3S) |
| 15 | 0 | fly ash |
| 13 | 18 | cement (C3S) |
| 13 | 0 | fly ash |
| 11 | 34 | cement (C3S) |
| 11 | 0 | fly ash |
| 9 | 77 | cement (C3S) |
| 9 | 0 | fly ash |
| 7 | 203 | cement (C3S) |
| 7 | 0 | fly ash |
| 5 | 578 | cement (C3S) |
| 5 | 0 | fly ash |
| 3 | 6903 | cement (C3S) |
| 3 | 0 | fly ash |
Name to be given to this microstructure:newcem (do not add a file extension as .img will be automatically added)
E-mail address:
Please be patient, may take 3-5 minutes to executive, once you press submit.
You will be e-mailed at the above address when execution is complete
Submit form to execute genpartnew
Return to the main menu
Figures 6-8: Form to create a starting 3-D particle microstructure.