The classification of hydraulic concretes into zones corresponding to the working conditions for individual parts of the structures and the use of different types of cement makes possible a discriminatory approach to concretequality requirement and the avoidance of their being set unjustifiably high and, in consequence, leading to cost increases for structures. However, the use of several types of cement in construction has its own undesirable aspects. This will be illustrated by specific examples.The design for the construction of the foundation structures of the Dneprodzerzhinsk hydroelectric station specified 18 concrete standards. Because the mixes used during construction have various workabittties and different aggregate sizes,and the cements delivered to the construction site may be of different standards and types, the total number of working concrete mixes increases 2 to 2.5 times; i.e., it becomes impracticable to provide the guaranteed standard in one and the same item. An unjustifiably increased number of concrete standards can lead to an inadmissible combination of differen:t mixes. Therefore, the number was reduced by grouping,and four concrete standards were finally adopted for the project.For the submerged parts of the structures, one concrete standard was adopted, namely R 200~0, W4,~ 0, Frs 50z8 , with a cement content of 235 kg/m s and W/C (water-cement ratio) = 0.55; for concrete in the zone of fluctuating water levels (spiral chamber without a slab facing or liners, spillway surfaces and the upper levels of dam apron slabs to a depth of 1.5 m) the adopted concrete standard was R200~0, W41s 0' Frs 100 ~, with a cement content of 265 kg/m 3 and W/C = 0.53; the interior massive structures of the lower portions of the apron stab, and of the upstream and downstream lock pier down to the zone of varying water levels, were constructed with concrete of standard R 150,g 0' W 4~0, with a cement content of 210 kg/m 3 and W/C = 0.57; the slopes of earth structures were protected with concrete of standard R 200~Q, W 4,~ 0, Frs 100~. with a c e m e n t content of 280 kg/m 3 and W/C = 0.53.Notwithstanding this radical reduction in the number of standards, the concrete plant in some instances had to deliver six or seven concrete mixes, depending on the type of cement, sizes of aggregates, and the requirements for workability of the concrete mix, art of which created certain difficulties.For the construction of the Kanevsk hydroelectric station, some 16 concrete standards were specified in the design, with aggregate sizes ranging up to 70 ram. Later, the Scientific-Research Station (NIS) of the Art-Union Scientific-Research and Design and Planning Institute of Hydrotechnicat Construction (Gidroproekt) reduced the n u mber of standards to eight; nevertheless, even this number is fairly high.The experience on previous structures had convincingly demonstrated that the number of concrete standards should not exceed three for the whole hydroelectric-station scheme. Experience has shown that a reduction in the numb...

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In the manufacture of hydraulic engineering concrete in the Soviet Union, extensive use is made of plasticizing and air-attracting surfactants [1, 2, 3]. The most popular additives are alcoholic sulfite waste (ASW) and sodium abietite (SA).Research conducted in the Department of Structural Materials of the V. V. Knibyshev Moscow Structural Engineering Institute (MISI) in recent years has shown that hydrophobizing surfactants have a marked effect on cement systems. Among such agents are products containing mainly naphthenic or higher aliphatic acids or their derivatives. Surfactants may be incorporated into the cement during grinding, or added directly to the concrete. In the first case, we achieve not only an improvement of a number of technical properties of the concrete, but also faster grinding of the cement and a marked reduction in the hygroscopicity, and therefore prolongation of the cement's activity. This paper gives results of a study of the effect of the most readily obtainable hydrophobizing engineering cements and concretes. The aliphatic acids used for this work were a mixture of saturated (about 60%) and unsaturated (about 40%) acids and hydroxy-acids of the carboxylic series in the range C~0-C~. In this form, aliphatic acids are a cheap by-product of our chemical plants.Method of Introducing the Hydrophobizing Agent. At normal temperature, aliphatic acids are highly viscous liquids which solidify at about 0*C. For incorporation into the cement, the agent must be added in fluid form, which is achieved by heating it to 50"C or by dissolving in organic solvents. The second method, which we used in our experiments, is more suitable for technological condit2ons. As the cement is being ground, a solution of aliphatic acids in the heavy fraction of petroleum hydrogenate (1 : 1 ratio by volume) is added. The viscosity of the solution, measured in an Engler viscosimeter in the range 5-30,C. is from 1000 to 270 cP, which ensures adequate fluidity. Addition of 0.2% of a solution of aliphatic acids renders the cement hydrophobic and speeds up grinding.Aliphatic acids are added with the mixing water in predispersed form for incorporation into mortar and concrete mixtures. Exothermy of Hydrophobic Cement and Concretes Based on it. A reduction in the exothermy of cement is particularly important for massive hydraulic engineering concretes. Determination of the heat of hydration of cement by the "Thermos" method stipulated in GOST 4798-57 revealed that incorporation of a hydrophobizing agent into cement reduces its exothermy, which agrees with the suggestion [4] that hydrophobizing surfactants have a stabilizing effect on cement setting.Experiments showed that aliphatic acids have the most marked retarding effect on hydration of tricalcium alurninate, which is accompanied by the highest thermal effect. A decrease in the evolution of heat by the cement is observed with even minimal additions of a hydrophobizing agent, and the decrease becomes disproportionately greater with increasing surfactant concentration. De...

It is a well-known fact that two opposite processes take place in concrete being cured by steam. One, which is beneficial, consists in the shaping and hardening of the texture of the setting concrete; the other, which is destructive, involves the deterioration of the texture as a result of the appearance of thermal and humidity gradients, as well as other causes. The application of surface-active admixtures may substantially improve the properties of steam-cured concrete and, primarily, increase its durability.Surface-active admixtures may be incorporated in the cement during pulverizing, or to the concrete mix along with the water. Surface-active substances have long been used for cast-in-place structures in hydraulic construction, but they have been rarely utilized in the production of precast elements at factories and construction yards. This is due to the fact that the admixtures used up to now (abietic resin, saponified wood pitch, naphthenate soap, sulfite-alcohol residue, and so on) in addition to having favorable effects on the characteristics of the steamcured products, including improvement of the impermeability, frost-resistance, and deformation properties, exhibit also undesirable effects on the concrete strength, especially in the case of severe heat-humidity treatment. In order to obtain a strength equal to that of concretes of similar composition, but lacking admixtures, it is necessary either to increase the amount of cement or to maintain the products under aging for a long time before subjecting them to the heat treatment. Long preliminary aging of the products is not economically advantageous for the factories.The work conducted at the department of construction materials of the V. V. Kuibyshev MISI (Moscow Civil Engineering Institute) in collaboration with the personnel of a chemical group of factories, as well as with various other organizations, indicated that if in the preparation of concrete mixes use is made of hydrophobic cements containing especially chosen admixtures (made from diverse products of the petroleum industry), then reduction of the strength of the products does not take place, even when particularly severe heat treatment and short preliminary aging are applied.The favorable results of preliminary investigations made it possible in 1964 to organize at a cement factory the production of two experimental batches of hydrophobic portland slag cement with an admixture of oxidized petrolatum, and then to place under service conditions, experimentally, the steam-cured products made with these cements.It is known that products made with portland slag cements are characterized by a lower frost-resistance as compared with ordinary portland cement products. For this reason the effect which may be obtained (from the standpoint of improvement of the frost-resistance) by the application of surface-active admixtures to portland slag cements is relatively lower than for portland cements. However, in connection with the fact that during the last years flag cement is being increasingly used i...