Wider application of slag portland cements in hydraulic construction

Abstract

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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