Chemistry hydration

And finally, appendices provide a user s guide for the FREZCHEM model and tables of model parameters. Version 9.2 of this model includes the precipitation-dissolution of chloride, nitrate, sulfate, and bicarbonate-carbonate salts of calcium, magnesium, sodium, potassium, and ferrous iron. This version also contains strong acid chemistries (hydrochloric, nitric, and sulfuric), gas hydrate chemistries (carbon dioxide and methane), and tem-perature/pressure dependencies. Electronic copies of the FORTRAN code are available from the senior author (giles.marion dri.edu). 

In pressure applications of the FREZCHEM model, the molar volumes of the neutral species CC>2(aq), 02(aq), and CH aq) are constants independent of temperature and pressure (Appendix B). This is similar to how solids are handled in the FREZCHEM model (see previous section). Of the gas-phase gases, only C02(g) and CHi(g) at high pressures in gas hydrate equilibria are assumed to be compressible (see the following section on gas hydrate chemistry). That means that other gas constituents such as H2O, O2, HC1, HNO3, and H2SO4 are only validly parameterized for low pressures (a few bars). 

Uchikawa (UI7) reviewed the hydration chemistry of pfa and other composite cements. Pfa cements differ from pure Portland cements notably in (i) the hydration rates of the clinker phases, (ii) CH contents, which are lowered both by the dilution of the clinker by pfa and by the pozzolanic reaction, (iii) the compositions of the clinker hydration products and (iv) formation of hydration products from the pfa. The two last aspects cannot be wholly separated. 

The rest of the chapter deals with the hydration chemistry of Portland and composite cements at temperatures outside the range 15-25 C, including that of autoclave processes, and with specialized uses of cements in casing oil wells and in making very high strength materials. 

Understanding of the chemistry of autoclave processes is due primarily to the work of Kalousek and co-workers (K32,K59-K62). Above about I. SO C. for the time scales of a few hours that are used in practice, two features of cement hydration chemistry are added to those relevant at lower temperatures. Firstly, the hydration products tend to crystallize in the absence of reactive silica, C-S-H tends to be replaced by a structurally unrelated, crystalline phase, a-CjS hydrate. Secondly, the range of siliceous materials having effective pozzolanic properties is widened, and includes quartz and various other crystalline minerals, if sufficiently finely ground. 

D. M. Oode, Carbdiydrate cyclic acetal formation and migration, Chem. Rev. 79 491 (1979). A. H. Haines, The selective tnoioval of protecting groups in carix>hydrate chemistry, Adv. Carbohydr. Chem. Blochem. 39 13 (1981). 

Q. Li, N.J. Coleman, Early hydration chemistry of white Portland cement in the presence of bismuth oxide, Adv. Appl. Ceram. 112 (2013) 207-212. 

Naphtalides, alkalides, and alkali metals are sufficiently powerful to reduce Ge and Si salts to the elements. Si nanocrystals have been prepared in solution by the reduction of the halides with Na, Li naphthalide, and hydride reagents [216-219]. Similarly, Ge nanocrystals have been made by the reduction of GeCL with Li naphthalide in THF [217]. TEOS (Si(OEt)4) is readily reduced by sodium to yield Si nanocrystals. Si and Ge nanocrystals are frequently covered by an oxide layer. Y2O3 nanocrystals have been made by the alkalide reduction of YCI3 followed by oxidation by exposure to ambient conditions [220]. Yittria nanocrystals could be doped with Eu to render them phosphorescent [221]. ZnO nanoparticles have been prepared from zinc acetate in 2-propanol by the reaction with water [222]. Pure anatase nanocrystals are obtained by the hydrolysis of TiCL with ethanol at 0°C followed by calcination at 87° C for 3 days [223]. The growth kinetics and the surface hydration chemistry in this reaction have been investigated. 

Ruthenium complexes are often inexpensive, readily available, and active catalysts for the hydration of alkynes [177-179]. In contrast to most mercury and gold systems, several of the Ru-based catalysts displayed a propensity to generate the anti-Markovnikov hydration products. One of the more practical approaches to this anti-Markovnikov hydration chemistry was developed by Herzon (Scheme 2.115) [180]. His approach entailed the use of a ruthenium compound bearing a 5,5 -(bistrifluoromethyl)-2,2 -(bipyridine) as the supporting ligand. A variety of ruthenium complexes could be isolated, and at least one... 

Fundamentals of concrete and Portland cements, hydration chemistry and classification of admix agents were reviewed by Kosamatka, Panarese and Soroka [84, 85]. 

Myers, R. J., E. L Hopital, J. L. Provis and B. Lothenbach (2015). Effect of temperature and aluminium on calcium (alumino)silicate hydrate chemistry under equilibrium conditions . Cement and Concrete Research 68 83—93. 

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