The low toughness of normal/conventional concrete (CC) motivated the advent of high-performance fiber-reinforced cementitious composites (HPFRCC) to control cracking and hence extend the service life of infrastructural elements. HPFRCC incorporating various constituents (50% cement, 50% slag, and 6% nano-silica), with single basalt fiber pellets (macro-BFP) or hybrid fiber systems including BFP and polyvinyl alcohol (micro-PVA) fibers at different dosages were extensively studied in this thesis. Fresh, mechanical and durability tests were conducted to investigate the properties of these innovative composites. Moreover, the synergetic evaluation of the flexural performance and single pellet pull-out in various homogenized nano-modified matrices was comprehensively explored using integrated experimental and modeling approaches. To investigate the potential of employing these composites as a filler in shear key bridge joints, the HPFRCC interfacial bonding capacity with CC under shear configurations, as well as its interaction with reinforcement steel rebars were experimentally and numerically studied. The results showed that nano-silica led to improved performance at early- and later-ages in terms of hardening rates, mechanical capacity, refinement of pore structure, resistance to freezing-thawing cycles, bonding with BFP and interfacial bonding with CC and steel rebars. Reduction in mechanical capacity and interfacial bonding with CC were observed for specimens comprising a higher dosage (4.5%) of BFP (single fiber system); however, the tensile strain hardening behaviour and rebar interfacial bonding capacity were improved with BFP dosage. Comparatively, 1% micro-PVA fibers with 2.5% or 4.5% macro-BFP (hybrid systems) resulted in marked improvement in terms of mechanical properties, durability to frost action, and interfacial bonding with precast CC and steel rebars. The synoptic outcomes of this thesis highlighted that nano-silica modified HPFRCC comprising hybrid fibers (G-N-V1-B2.5 and G-N-V1-B4.5) can be a practicable option for shear key joints with enhanced performance in terms of mechanical and durability properties, as well as bonding capacity with CC and shear reinforcing dowels. The developed finite element models herein could efficiently project the expected full-scale behavior of complex composites such as HPFRCC including its shear capacity, crack formation process, and modes of failure, which pave the way for field applications.