• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.3
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• pp.139-148
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• 2015

The purpose of this paper is to induce the ductile behavior of the UHPFRC member after the peak load by using the bundle of longitudinal reinforcing bar as a substitute for steel fiber. Experiments on the flexural behavior of the Ultra High Performance Concrete rectangular beam with the combination of the steel fiber and longitudinal reinforcing bar were carried out. The volume fractions of steel fiber are 0%, 0.7%, 1%, 1.5%, 2% and the reinforcement ratios of longitudinal reinforcing bar which induce the ductile behavior are 0.0036, 0.016, 0.028 and 0.036. 15 UHPC beams were made with the combination of these test factors. Not only steel fiber but also bundle of longitudinal reinforcing bar has the effect to induce ductile behavior of UHPC structural member. The combination of 0.7% volume fraction of steel fiber and 0.028 reinforcement ratio showed the most economic combination. The relationship of load-deflection, strain variation of the concrete and the crack pattern indicate the usefulness of the bundle of the longitudinal bar which has small diameter with close arrangement each other.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.1
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• pp.11-18
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• 2018

As the amount of polycarboxylate superplasticizer varied from 1.2% to 3.0% of the mass of binder, the change in the flowability & rheological properties, and strength of UHPFRC was investigated with experiments. The test results presented that the increase in the amount of superplasticizer was effective in improving the flowability up to 1.8%, but addition more than 1.8% was hardly beneficial for enhancing the flowability and rhelogical properties. Compressive strengths with different amounts of superplasticizer showed that the strength with 1.8% was slightly higher than that of 1.2%, but the amount more than 1.8% caused strength reduction, which was higher as the amount increased. The results in flexural strength according to the amount of superplasticizer showed a similar trend with the results in compressive strength. When the effect of compressive strength and fiber distribution characteristics on the flexural strength was analysed separately, it was found that high amount of superplasticizer caused an effect of fiber distribution in addition to the effect of compressive strength on flexural strength. This effect seems to be closely related to the results of flowability or rheological properties.