The physicotechnicaL properties of synthetic structural materials depend largely on the homogeneity of the starting mixtures and the finished articles [1,2]. A decrease in homogeneity usually leads to deterioration of the properties, particularly in the case of concretes for hydraulic structures. Such concretes are characterized by a relatively low cement consumption, so that uniform cement distribution in the concrete presents difficulties. Owing to fluctuations in the moisture content of the aggregates, the plastic-viscous properties of the mixtures may vary widely, which has a deleterious effect on the homogeneity of the hardened concrete. Concrete mixers have large mixing compartments and the period of mixing is very brief, which reduces the possibility of obtaining uniform masses. Transport of the concrete mix over long distances leads to layer separation (which is also observed during compaction by vibrators).From data in the literature and practical experience, we know that the addition of surfactants to cement Or concrete improves the homogeneity of the latter and its principal physicomechanical properties, owing to the specific character of the effect of such additives on cement systems [3, 4]; e.g., additives which render concrete hydrophobic have a plasticizing effect, or reduce the viscosity of concrete mixes under mechanical influences (mixing and vibration). However, the flocculating effect of such additives prevents layer separation of concrete mixes during discharge, transport, and placing. This paper deals with the homogeneity of hydraulic concretes in relation to their principal physicomechanical properties and with the effect of various surfactants on these characteristics.The criteria presently used in factories and research laboratories for assessing the homogeneity of mixtures enable us to make only an indirect and somewhat subjective judgment (after much time has been expended) of the homogeneity and subsequent layer separation of the principal components during transport and placing.The homogeneity of a mixture, obtained during its preparation, is usually assessed from the results of tests on the most characteristic properties of the materials after all operations have been performed. For concretes and mortars, the relevant properties may be the unit weight or strength indices of specially fabricated specimens. However, these indices depend on a number of technological factors, which naturally distort the true picture; furthermore, determination of the strength, for example, is performed on specimens of 3-, 7-, and 28-day age. Therefore, intense research has been performed in order to develop practical, rapid methods of assessing the homogeneity of mixes, the most promising of these being the radioactivity method and the method of luminophors. The first method, based on the use of radioactive specimens, requires the construction ofa specialisotope laboratory, and also complex safety procedures.The Luminophor Method. The rapid method of determining the optimal operational indices of mixing ...

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