Flocculating admixtures

The chief function of these admixtures is to reduce the destructive type of bleeding to a more gradual seepage in mixes. The materials include 

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The power dependence of p on defines the strong dependence of Q on Thus, for twofold increase of Q value for PDMDAAC with AZM=3xl0 D reduction from 1.65 up to 1.50 is required at constant flocculator concentration. As it is known through Ref. [1], the exponent a value in Mark-Kuhn-Houwink equation depends on a type of the solvent, used at measurements, therefore macromolecular coil conformation can be changed by the last suitable choice and this way to control its ability to flocculate admixtures. This ability control can be performed by the exponent variation and measurement—as it follows from the Eq. (4), increasing means reduction. 

Adsorption of the admixture on the hydrating cement grains could decrease flocculation in at least three ways (D44). The first is an increase in the magnitude of the ( -potential if all the particles carry a surface charge of the same sign and sufficient magnitude, they will repel each other. The second is an increase in solid- liquid affinity if the particles are more strongly attracted to the liquid than to each other, they will tend to disperse. The third is steric hindrance the oriented adsorption of a non-ionic polymer can weaken the attraction between solid particles. 

Water reducers and superplasticizers. Admixtures aimed at increasing the workability of concrete are chemical substances that improve the mobihty of the particles in the fresh concrete mix by increasing the effectiveness of the mixing water. They contain surface-active agents that are adsorbed on the surface of solid particles and modify their electrical surface charge, so that they do not tend to flocculate, and thus are more dispersed, and the water can better lubricate the mix. 

Hence, the increase of TMAC contents in copolymers PAA-TMAC has two consequences for macromolecular coil stmcture the chain rigidity increase and macromolecular coil fractal dimension reduction is observed. These changes influence essentially on both synthesis processes and flocculation of low-molecular admixtures processes of the considered copolymers [36]. 

Secondly, this plot shows very strong dependence of p on MM, that in its turn explains macromolecular coil accessibility degree strong enhancement in respect to admixtures (phosphatides) penetration in its internal regions and, hence, the strong dependence of flocculator (PDMDAAC) optimal concentration c on MM [183],... 

Hence, the stated above results have shown that the molecular weight, macromolecular coil stmcture, characterized by its fractal dimension, and medium, in which flocculation occurs, are included in a factors number, influencing on adsorption of admixtures (flocculation) effectiveness by a pol mier flocculator PDMDAAC. The medium cans influence on flocculation process by two ways by a macromolecular coil fractal dimension change and viscosity variation. The latter factor can influence on diffusive processes intensity. The sole from the enumerated above factors, which will influence equally on fractal and compact objects properties, is a... 

Kozlov, G. V Malkanduev Yu.A. Mirzoeva, A. A. The fractal model of flocculation process of low-molecular admixtures by polymeric flocculator. Proceedings of IV International Sci.-Pract. Conf The Economics of Usage and Protection of Nature. Penza, PSU, 2001,153-156. 

Thus, TMACh contents increasing in copolymers PAA-TMACh has two consequences for macromolecular coil structure — the chain rigidity increasing and the coil fractal dimension reduction are observed. These changes inflnenced essentially on both synthesis process and low-molecular admixtures flocculation of the considered copolymers. 

The soya bean phosphatide insoluble in alcohol has a very low I. E. P. and also a very low colloid equivalent weight, with which is connected the fact that even in aqueous medium (without addition of auxiliary substances, see note 3, p. 405) complex flocculation occurs with 3 and 2-valent cations. According to the N P ratio = 2 1 one can here expect a considerable admixture of phosphatidic acid. 

This hydrophobization, linked to a decrease in the negative value of the -potential by the admixture of small amounts of plurivalent counter ions, has been shown to cause flocculation of a variety of initially stable particle suspensions, e.g., calcite powder, montmorillonite (SWy-1) particles (Wu, 1994 Wu et al, 1994a,b). The flocculated particles could be reconverted to a stable suspension by complexation of the di- and trivalent counterions with, e.g., EDTA or hexameta phosphate (Wu, 1994). Upon standing for about 16 hours, the flocculated suspensions repeptized spontaneously, as a result of intercalation of the counterions into the clay particle structure (Wu, 1994). 

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