Study of changes in strength properties along section thickness of high-strength centrifuged and vibro-centrifuged concrete

Improving the efficiency of precast concrete products and structures can be achieved by creating thin-walled products of effective cross-sections from high-strength concrete the formation of which requires application of centrifugal methods of compaction. The paper discusses literature data on the issue of forming the structure of centrifuged concrete by the thickness of the section wall, taking into account different densities of the components of the molded concrete mass under the action of centrifugal forces during mold rotation during concrete compaction at a constant speed. The authors conducted a series of experimental studies to establish the nature of the change in strength properties along the thickness of cross section of products from heavy concrete made by centrifugation and vibrocentrifugation. As a result of experiments, it was found out that the density of samples of centrifuged structures decreases in cross section from the outer layer to the inner one. The greatest values of ultimate strength under axial compression and tension during bending are characterized by the outer layer, the smallest are characterized by the inner layer. The middle layer in terms of strength indicators is close to the average strength of the whole product. A feature of changes in compressive and tensile strength during bending of vibro-centrifuged products and structures compared to centrifuged layers is a smaller difference between the outer and middle layers and a significant difference between the outer and inner layers. It was established that the variability of the structure of high-strength concrete is less pronounced compared to the lower-grade concrete.