Concrete strength tendency in the wall of cylindrical spun-cast concrete elements

Abstract

The aim of the research was to characterize the concrete mixtures for spun-cast concrete and to determine the relationship between the compacting ratio and the manner of segregation. In the research 23 specimens of 9 different mixtures with low w/c ratio were tested. Investigated parameters included w/c, spinning speed, duration, and properties of the aggregate. The strength of the concrete in the outer, middle and inner region of the spun-cast element and of the vibrated cube was assessed by testing drilled cores. The optimal compacting energy caused by spinning was defined for different mixtures. Statistical regression functions depending on the parameters above were defined for the change of strength in the wall of the element.Keywords spun-cast concrete · strength · experimental test AcknowledgementThe authors wish to express their gratitude to BVM Épelem LTD, SW Umwelttechnik Hungary LTD, Railone LTD for the research materials and for sponsoring the research. Thanks to the Department of Structural Materials and Engineering Geology for their assistance in the laboratory work. Special thanks to Mr András Eipl. István VölgyiDepartment of Structural Engineering, BME, Bertalan L. u.

Rebound testing of cylindrical spun-cast concrete elements

“…Correlations between the strength of the spun-cast and of vibrated elements made of mixtures with low w/c ratio have been published by the authors earlier [16][17][18]. Due to radial segregation the composition of the material and its strength changes throughout the wall of the element.…”

“…It has been shown that the composition of the material changes throughout the wall of the specimen due to the radial segregation. The incidence of gravel is higher in the outer region because of its higher density [18]. The result of rebound tests strongly depend on the properties of the microenvironment.…”

“…A polynomial regression function was determined for the f cm,out / f cm,vib ratio and for the f cm = ( f cm,out − f cm,in )/ f cm,out ratio, as function of the E * app /E * need ratio and paste excess [15]. See more about this topic in [18]. The functions are shown in Fig.…”

“…Applied enlarged compaction energy is a production of the pressure at the outer radius of the specimen caused by the centrifugal effect and the compaction time. Compression classes have been defined in [18] after the applied compaction energy. The cylindrical compressive strength of concrete was determined using drilled cores from the inner, middle and outer region of spuncast specimen and from the vibratory compacted specimens (Table 2).…”

“…Spinning concrete at high speed may cause segregation and different porosities within the concrete wall, which leads to different shrinkage and strength [11]. Previous research by the authors [18] shows that the strength properties of the spun-cast elements significantly depend on the spinning parameters. Quality control using vibrated specimens made of the same mixture is not the best method.…”