Impact of Steel Fiber Volume Fraction and Morphology on the Strength of Recycled Aggregate Concrete

Steel-fiber-reinforced recycled coarse aggregate concrete (SFRCAC) has great potential for use in structural members due to environmental and economic reasons. A comparison of SF’s reinforcing effect on the strength of RCAC with natural recycled coarse aggregate concrete (NCAC) was conducted through experiments and analysis. Three types of steel fiber—milling (MF), shear-wave (SWF), and both-end hooked (BF)—were used. The SF volume fraction (Vf) was taken as 0, 0.5%, 1.0%, 1.5%, and 2%. The results show that SF has a similar reinforcing effect on NCAC and RCAC. The reinforcing effect of SF on the strength of RCAC is relevant to the strength of the RCAC matrix. The suitable content range of SF is from 0.5% to 1.5% in terms of the reinforcement effects on the compressive strength (ffcu) and splitting tensile strength (ffts) of RCAC. SF with a higher aspect ratio (AR) has a better reinforcing effect on the splitting tensile strength (ffts) and flexural strength (fftm) of RCAC. The equations of ffts/fts and fftm/ftm with the characteristic parameters of steel fiber (λf) were put forward to accurately determine the dosage of SF.

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