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Experimental assessment of the casting position factor of reinforcing bars in high performance concretes (HPC, HPSCC)

Dybeł Piotr, Kucharska Milena

Archives of Civil and Mechanical Engineering

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2019

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Vol. 19, no. 1

127--136

EN

This paper concerns the problem of the experimental assessment of the casting position factor in comparison to the current normative guidelines. Our experiment was performed on three types of concrete: high-performance concrete (HPC), high-performance self-compacting concrete (HPSCC) and normal strength concrete (NSC) used as a reference. The HPC and the HPSCC were made in respectively, two and four different variants that differed in the content of silica fume. To assess the casting position factor, three types of elements with heights of 480, 800 and 1600 mm were used. In each element, a ribbed reinforcing bar with a diameter of 16 mm was embedded perpendicularly to the direction of concreting. The bond was examined using pull-out test. The test results showed that regardless of the type and composition of concrete, the linear change of the casting position factor with element's height was observed. No significant differences in the changes of the casting position factor with height were noted between the HPC and the HPSCC. The experiment revealed that the new generation concretes were characterized by a much lower value of the casting position factor in comparison to the current normative guidelines.

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The effect of ribbed reinforcing bars location on their bond with high-performance concrete

Dybeł P., Furtak K.

Archives of Civil and Mechanical Engineering

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2015

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Vol. 15, no. 4

1070--1077

EN

This paper deals with the effect of reinforcing bars location on high-performance concrete–rebars bond. The results of research have proved that the increased distance of the reinforcement from the formwork bottom (a larger layer of concrete below the bar) decreases the bond. The physical bases of the phenomenon are related with a special form of bleeding in which process a portion of water is transported towards the upper surface of concrete mix. The modified microstructure and different mechanical properties of high-performance concrete result in the fact that the maximum bond differences between the area of “good” and “poor” bond conditions are much smaller than in normal concretes. Following the results of experimental research it can be stated that concrete-upper bars bond reduction quoted in standard guidelines is rather conservative. Therefore, it has been found advisable to determine new criteria of bond conditions assessment for high-performance concrete.

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Assessment of the casting position factor in reinforced concrete elements in view of experimental studies

Dybeł P., Furtak K.

Archives of Civil Engineering

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2014

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Vol. 60, nr 2

209--221

EN

The paper presents the results of experimental investigations performed by the authors on the casting position factor. It was proved that at the height of reinforced concrete elements there are different bond conditions. Moreover, the bond depends on concrete mechanical properties, element height as well as concrete mix composition and consistency. The experiments also showed the advisability of determining the casting position factor separately for bars from normal concrete and those from high–performance concrete (HPC). The analysis of investigation results has shown that “good” bond conditions are a relative concept and depend on, among other things, element height. The higher the element the better the concrete to lower bars bond. Consequently, elements of considerable height (higher than 600 mm) demonstrate a bigger difference between concrete to upper bars bond and concrete to lower bars bond.