Cementing model

The Touchstone quartz cementation model assumes that the precipitation rate per unit nucleation surface area is described by an Arrhenius kinetic expression (Walderhaug 2000) and that the nucleation surface area for quartz overgrowths is a function of grain size... 

Fig. 19. Results of compaction and quartz cementation models calculated using quantitative petrographic data, Touchstone and the thermal history shown in Figure 16. (a) Calculated versus observed IGV 4% tolerance, (b) Calculated versus observed quartz cement volume 3% tolerance, (c) Calculated versus observed intergranular porosity 4% tolerance.

Computer Model of Thermal Processes in a Cement Kiln for Application in IR Defectoscopy. 

The given computer model of thermal processes in a cement kiln allows to calculate temperature pattern both at a surface and inside a kiln body. 

Sticky waxes are used as thermoplastic cements. The broken pieces of a plaster impression are reassembled and held in position with sticky wax. Broken denture bases may be held in proper alignment for repair. Orthodontic apphances may be assembled with a sticky wax prior to investing and soldering. Plaster splints may be sealed to stone models in the production of porcelain or resin facings. Thus, sticky wax is useflil in almost any operation where it is desired to position and hold several small pieces in a temporary relationship. 

They are used by direct placement in tooth cavities or by custom fabricating using composites on a gypsum model of the cavity and then cementing the restoration into the tooth cavity. 

This design was closely followed in the experimental model and in the later instruments. The experimental model (October, 1940) had as test body a dumbbell of two thin-walled glass spheres 4 mm. in diameter sealed to a glass rod 6 mm. long. A silica fiber 8 fi in diameter was stretched between the prongs of a silica fork, and the glass dumbbell was cemented with shellac to the middle of the fiber, perpendicular to it. A plane glass mirror 2 mm. square was also cemented near the middle of the fiber. The suspension was balanced... 

Rotty, R. M. (1981). Data for global CO2 production from fossil fuels and cement. In "Carbon Cycle Modeling" (B. Bolin, ed.), pp. 121-125. Wiley, New York. 

The waste management situation in Austria is presented, and it is explained that Baufeld-Austria GmbH has developed a method and concept, with the eooperation of cement plant experts, to enable some Austrian eement factories to responsibly use plastics waste as an energy source. The conditions used for developing the model, relating to fuel quality, environmental proteetion, and public health, are explained. The Baufeld model for processing of plastics waste is then described. Details of future plans are included. 

The picture of cement microstructure that now emerges is of particles of partially degraded glass embedded in a matrix of calcium and aluminium polyalkenoates and sheathed in a layer of siliceous gel probably formed just outside the particle boundary. This structure (shown in Figure 5.17) was first proposed by Wilson Prosser (1982, 1984) and has since been confirmed by recent electron microscopic studies by Swift Dogan (1990) and Hatton Brook (1992). The latter used transmission electron microscopy with high resolution to confirm this model without ambiguity. 

Hetem, S., Jowett, A. K. Ferguson, M. W. (1989). Biocompatibility of a posterior composite and dental cements using a new organ culture model. Journal of Dentistry, 17, 155-61. 

Kuhn, A. T. Jones, M. P. (1982). A model for the dissolution and fluoride release from dental cements. Biomaterials, Medical Devices and Artificial Organs, 10, 281-93. 

Kuhn Jones (1982) examined various models for fluoride release and showed that release did not fit the membrane and homogenous monolith model. Instead, they concluded that the cement behaved as a porous granular monolith, as described by Kydonieus (1980). The release of fluoride appears to be an ion exchange phenomenon, as dental silicate cement takes up rather than releases fluoride from solution if it is present in sufficient concentration (Kuhn, Lesan Setchell, 1983). 

Several features of the early model (Fig. 6) have been modified in the present-day, high-temperature version of this calorimeter (Fig. 7) (37). Depending upon the temperature range envisaged, the block is made of refractory steel, alumina, or beryllium oxide and is machined to house the calorimeter itself. The thermoelectric pile (about 50 platinum to platinum-rhodium thermocouples) is affixed in the grooves of an alumina plate (A), which is permanently cemented to two cylindrical tubes of alumina (B). Cylindrical containers of platinum (C) ensure the uniformity of the temperature distribution within the calorimeter cells. 

In light of the small solubilities of many minerals, the extent of reaction predicted by this type of calculation may be smaller than expected. Considerable amounts of diagenetic cements are commonly observed, for example, in sedimentary rocks, and crystalline rocks can be highly altered by weathering or hydrothermal fluids. A titration model may predict that the proper cements or alteration products form, but explaining the quantities of these minerals observed in nature will probably require that the rock react repeatedly as its pore fluid is replaced. Local equilibrium models of this nature are described later in this section. 

The rock in question might contain a large amount of calcite cement, but the reaction path predicts that only a trace of calcite forms during burial. Considering this contradiction, the modeler realizes that this model could not have been successful in the first place there is not enough calcium or carbonate in seawater to have formed that amount of cement. The model in this case was improperly conceptualized as a closed rather than open system. 

The reservoir rock in our model is composed of quartz grains, carbonate cement, and clay minerals in the following proportions, by volume ... 

---