Reliability of pull-off test for steel fiber reinforced self-compacting concrete

• The application of pull-off test for steel fiber reinforced SCC is assessed.
• The effect of disc characteristics, partial coring and steel fiber content are probed.
• For core depths of ⩾10 mm, the reduction in pull-off load is independent of core depth.
• The stiffness of the disc is an important parameter for interpretation of results.
• A specific calibration curve must be developed for each SFR and plain SCC concretes.

This study investigates the applicability of pull-off test in more detail to prepare appropriate outlines for assessing the in-situ quality of steel fiber reinforced self-compacting concrete (SFRSCC) in order to minimize uncertainties involved. For this purpose, an extensive experimental program was conducted including different cement contents of 400 and 500 kg/m3, two maximum aggregate sizes of 10 and 20 mm along with steel fiber contents of 0, 30, 50 and 80 kg/m3. In this study, the water/cement ratio was kept constant at 0.45 for all mixes. 50 mm diameter aluminum and steel discs with thicknesses of 10, 20 and 30 mm along with 70 mm diameter aluminum and steel discs with thicknesses of 10 and 30 mm were supplied. Moreover, to examine the effect of partial core depth on pull-off strength, three different depths of 10, 30 and 50 mm for 50 mm diameter discs and two different depths of 20 and 50 mm for 70 mm diameter discs were chosen. The material and proportions of discs, partial coring and steel fiber content are shown to be particularly significant in pull-off test results for SFRSCC. Also, it is recommended that a specific calibration curve must be developed for each SFR and plain concretes with particular attention to disc characteristics for interpretation and comparisons of results to make a realistic assessment.

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