Water void spaces

As a result of the linear expansion, the reduced volume of the dihydrate, and the evaporation of excess water, the percentage of void spaces in plaster is ca 45%, in stone 15%, and in improved stone 10%. Thus, the additional amount of water required for plaster contributes to the volume but not to the strength of the hardened material (105). 

At the end of the mixing process, the paste contains about 10wt% of metallic lead and about 50vol.% of water. The water is evaporated during the subsequent production steps, and the resulting void space represents the pore volume of the dried active material. 

A further longer term wet lay-up alternative is through the use of volatile corrosion inhibitors (VCIs) such as dicyclohexylamine acetate. These are dissolved in the water at a temperature below 60 °C, and the water is circulated for 4 to 5 hours. The boiler does not need to be completely filled because the VCI migrates to all parts of the boiler and reaches equilibrium in each of the void spaces. With traditional lay-up chemicals, the oxygen scavenger may become depleted easily (which is why the reserve usually is so high) and corrosion protection is quickly lost however, with VCI programs, there is always a volatile buffer available that maintains equilibrium and hence corrosion protection. 

Hydraulic conductivity is one of the characteristic properties of a soil relating to water flow. The movement of water in soil depends on the soil structure, in particular its porosity and pore size distribution. A soil containing more void space usually has a higher permeability. Most consolidated bedrocks are low in permeability. However, rock fractures could create a path for water movement. 

All voids in the subsurface medium are classified as porosity. When pore spaces are interconnected so that water can flow between them, the medium is said to be permeable. The actual openings that permit water flow are referred to as effective porosity. Effective porosity is calculated as the ratio of the void spaces through which water flow can occur to the bulk volume of the medium (expressed as a percentage) as follows ... 

Injection into unsaturated deposits must also consider that when the injected water leaves the injection tubing, it is at atmospheric pressure, and the driving head is lost which lowers injection efficiency. In addition, the capillary and surface tension forces in the void spaces provide resistance to water movement, thus limiting injection efficiency. Injection into only the saturated zone (Figure 8.8b) maintains a positive head pressure on the water until it exits the well screen. This limits the chemical reaction that might occur in the well bore. Since the void spaces are saturated, there are no capillary or surface tension forces to overcome. 

In the vadose zone, liquid or dissolved contaminants exist in a complex environment that involves interaction among the chemicals, soil grains, water attached to soil grains (or between the soil pores), the atmosphere in void spaces, and numerous... 

For a fast catalytic reaction, free access of gas, electrons, protons and water is needed. This leads to a best compromise of the volume fractions of protonconducting polymer, electron-conducting carbon, active sites and void space. 

Because no single homogeneous phase could fulfill these conflicting needs simultaneously, CLs require composite morphologies that consist of several interpenefrafing phases. A minimum of fwo distinct phases is needed, including a solid phase of nanoparticle catalyst (Pt) and electronically conducting substrate (carbon) and a liquid water phase in the void spaces of the substrate for diffusion and permeation of protons, water, and reactant molecules. 

PAMAM dendrimers are large (G4 is 4.5 nm in diameter) and have a hydrophilic interior and exterior accordingly, they are soluble in many convenient solvents (water, alcohols, and some polar organic solvents). Importantly, the interior void spaces are large enough to accommodate nanoscopic guests, such as metal clusters, and are sufficiently monodispersed in size so as to ensure fairly uniform particle size and shape. As we will show later, the space between the ter-... 

It has been previously reported [21, 22] that metal colloids are formed by radiochemical reactions in water/alcohol solutions, in which the reduction of metal salts takes place by solvated electrons and free radicals produced under UV or y-ray irradiation. Ichikawa et al. have applied this photoreduction method to the surface-mediated reaction of metallic ions and succeeded in synthesizing metal/aUoy nanowires in the constrained cavities of mesoporous supports such as FSM-16 and MCM-41 [18-20, 23-25]. The adsorbed water and alcohol work not only as solvents in the nanoscale silica void space but also as a source of reducing species for metallic ions to metals under UV-vis and y-ray [11, 18, 19] irradiation. The results indicate the dense formation of Pt nanowires inside the charmels of mesoporous supports, such as FSM-16, which act as the templates. In fact, no any Pt wire is observed on the external surface of FSM-16 or amorphous silica surface. Short wires, 10 nm long, are also observed as a minor species in the samples in the initial stage of UV and y-ray irradiation. 

A crack is an open fissure, whereas a craze is spanned top to bottom by fibrils that act to resist entrance of opportunistic molecules such as water vapor. Even here, some smaller molecular interactions can occur within the void space, and eventually the specimen is weakened. 

Water-cement ratio (by wt) Nature of mix Air content (%) Paste content (%) Voids in concrete (%) Specific surface area (mm) Void spacing factor (mm)... 

The amount of air space available in relation to the expansion of that part of the water likely to freeze. In theory, the amount of void space necessary is about 4% of the paste volume but, in practice, because of the distribution of void sizes formed and because the total volume of the voids could not be filled by the ice which would already be in the solid form on entering the void, greater air contents are required. The recommendations shown in Table 3.21 are made. 

Air content of field mixes varies very little for mixing periods between 10 and 25 min and retempering with water to increase the slump from 50 to 100 mm has no significance on the air-void spacing factor, although it results in a small increase in the air content. 

In closing this section, remember that Aristotle rejected the concept of atoms. Aristotle could not accept the idea of a void space and believed that nature abhors a vacuum. Furthermore, Aristotle did not consider internal structure. Substances contained their qualities and elements as a homogenous mixture. An Aristotelian would explain the reaction of hydrogen gas and oxygen gas to produce liquid water as... 

Gas hydrates behave as solutions of gases in crystalline solids rather than as chemical compounds. The main framework of the hydrate crystal is formed with water molecules. The hydrocarbon molecules occupy void spaces within the lattice of water molecules. 

Hydrate formation is physical rather than chemical in nature. Apparently, no strong chemical bonds are formed between the hydrocarbon and water molecules. Actually, the hydrocarbon molecules are free to rotate within the void spaces. 

It has been widely demonstrated that injection of water into both PTFE-treated and untreated GDMs requires positive capillary pressure while water withdrawal requires negative capillary pressures, where capillary pressure is defined as Pc = Pl — Pg- Various explanations for this behavior have been put forward, including contact angle hysteresis,59 the converging-diverging nature of void space... 

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