Investigating stress-strain relationship and damage constitutive model of basalt fiber reinforced concrete under uniaxial compression

Basalt fiber is a useful reinforcing and toughening material for concrete. The stress-strain relationship and damage evolution of concrete under compression can provide an experimental and theoretical basis for the design of structures. This research conducts uniaxial compression tests on basalt fiber reinforced concrete (BFRC) specimens with five different strength grades, namely BFRC25, BFRC30, BFRC40, BFRC50, and BFRC60, to investigate their stress-strain relationship. Digital image correlation (DIC) technology was adopted to analyze the damage evolution during the compressive loading process. Results revealed that with increasing the strength grade of BFRC, the peak stress and elastic modulus increased, the peak strain varied insignificantly, and the ratio of the ultimate strain to peak strain decreased. Considering the effects of the strength grade and fiber, a segmental constitutive model for predicting the stress-strain relationship of the BFRC was developed. In addition, the analysis of the transverse strain cloud diagrams collected by DIC revealed the local strain concentration phenomena during compressive damage to BFRC. The damage constitutive model considering the factors of strength grade and fiber was established, which can predict the compressive damage process of the BFRC specimens.