Cementitious substances

Asphalt [8052-42-4] is defined by the American Society for Testing and Materials (ASTM) (1) as a dark brown to black cementitious material in which the predominating constituents are bitumens that occur in nature or are obtained in petroleum processing. Bitumen is a generic term defined by ASTM as a class of black or dark-colored (soHd, semisoHd, or viscous) cementitious substances, natural or manufactured, composed principally of high molecular weight hydrocarbons, of which asphalts, tars, pitches, and asphaltites are typical. 

The phosphate bonded cements described in this chapter are the products of the simple acid-base reaction between an aqueous solution of orthophosphoric acid and a basic oxide or silicate. Such reactions take place at room temperature. Excluded from this chapter are the cementitious substances that are formed by the heat treatment of aqueous solutions of acid metal phosphates. 

Relating in general to bituminous materials Bitumen—a class of black or dark-colored (solid, semi-solid, or viscous) cementitious substances, natural or manufactured, composed principally ofhigh molecular weight hydrocarbons, of which asphalts, tars pitches, and asphaltites are t5 ical. 

The siliceous and aluminous contents of the effluent from the TSA [6], should be tested for their affinity to the hydraulic lime to form cementitious substances (termed as the special cement). Once experimentations are planned and attempts are made to monitor the physical, chemical, mineralogical and morphological characteristics of such special cement, the inferences would pave some way to a further step ahead towards establishing an innovative fly ash zeolite synthesis technique with zero-emission waste for a safer environment... 

Another field with a large potential for improvements concerns aluminosilicate minerals, which are of great importance in determining the chemistry of water in many types of rock. In backfill clays, aluminosilicates are responsible for the retention (sorption, incorporation) of trace elements and may affect both oxidation potential (incorporation of Fe(II)/Fe(III)) and pH (hydrolysis of silicate and/or exchange of H+). Related classes of compounds (i.e., calcium silicates and calcium aluminates) form the chemical backbone of cementitious materials. The thermodynamic properties of these substances are still largely unexplored. 

Cocke, D. L. Molla, M. Y. A. 1993. The chemistry and leaching mechanisms of hazardous substances in cementitious solidification/stabilization systems. In Spence, R. D. (ed) Chemistry and Microstructure of Solidified Waste Forms. Lewis, Boca Raton, 187-242. 

However, in cementitious material, research related to the diffusion coefficient, the permeation coefficient, and quantification of the electric mobility has just made a start, and models corresponding to various materials and environmental conditions have not yet been constructed as of this stage. In the past, apparent diffusion coefficients were used including aggregates as shown on the left side of Fig. 4, but in practice, substances such as pore solution and ions did not move within the aggregates or the hydrates themselves, but they can move in capillary porosity and transition zones. Thus, an effective diffusion coefficient D, calculation equation is proposed as... 

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