Basalt fiber (BF) is an environmentally friendly type of fiber that has attracted the attention of researchers in recent years due to its excellent performance in concrete constructions. This current research was conducted to investigate the effect of chopped basalt fiber on the workability, compressive strength, and impact resistance of high-performance concrete (HPC). Three various lengths (3, 12, and 18 mm) and six volume fractions (0%, 0.075%, 0.15%, 0.3%, 0.45%, and 0.6% by concrete volume) of BF were used in producing sixteen HPC mixes. HPC compressive strength and impact resistance were measured for each mix. Scanning electron microscopy (SEM) analysis was also conducted on selected mixes to closely investigate the effects of the applied variables through the microstructural scale. An empirical model was developed to study the relationship between the impact energy and compressive strength of BF-reinforced HPC. The results show that adding BF improves the compressive strength and impact resistance. Compared with the control concrete, the compressive strength of the HPC reinforced with 3 mm, 12 mm, and 18 mm BF increased by 12.2%, 15.1%, and 17.5%, respectively. The impact resistance increased with a dosage of 8 kg/m³ for all lengths of BF. The SEM observations revealed that the BF accumulated in pores and on the surface of the attached cement which improved the microstructure of the interfacial transition zone (ITZ), which further enhanced the strength and ductility of the HPC.

Functionally graded concrete (FGC) is a construction technique that helps the structures to adapt to varying structural and functional requirements. In this study, eco-friendly engineered cementitious composites (ECC) mixes made of stone processing waste (SPW), crumb rubber (CR), and hybrid basalt fibers (BF), were developed and employed in FGC beams to improve their flexural performance. In the proposed eco-friendly ECC mixes, SPW, and CR were used as partial substitutions of the conventional ECC fine aggregate volume by 20%. Several types of SPW were used including basalt waste (BW), dolomite waste (DW), and marble waste (MW). The slump, slump-flow, compressive strength, and uniaxial tensile strength were measured for the eco-friendly ECC mixes. In addition, eight reinforced FGC beams (130 × 230 × 1000 mm) were prepared and tested. The beams included different configurations in which the proposed ECC mixes were employed in the beam tension zone (bottom one-third). The structural performance of the proposed FGC beams was assessed through testing them under a 4-point bending loading. The results indicated that the utilized SPW and CR decreased the ECC by 15.0–33.3%. CR reduced the ECC's compressive and tensile strengths by 28.1% and 11.2%, respectively. The BW improved the compressive and tensile strengths of ECC by 7.14% and 14.3%, respectively as opposed to the reference ECC. The use of BW consequently enhanced the flexural performance of the FGC beams. The FGC beams showed an enhanced ductility with using eco-friendly ECC. The FGC beams made with CR-ECC and BW-ECC achieved the highest deflections of 16.46 mm and 15.35 mm (73.9% and 62.2% higher than that of beam made with control ECC), despite slight reductions in their peak loads making them suitable for applications requiring high ductility. Graphical abstract