## 2 State-of-the-Art  
Recent years have seen significant strides in concrete technology, propelled by advances in chemistry and materials science. The introduction of innovative fillers into cementitious matrices has played a crucial role in elevating the mechanical properties and durability of materials [16]. [PERSON] at al. [17] demonstrated, through laboratory tests, that hybrid carbon fiber mixes exhibited superior tensile performance, improving the mortar's fracture resistance, although all the fiber reinforcement enhanced the pre-peak load energy absorbing capacity. In particular, carbon nanofibers (CNFs) and milled carbon microfibers (MCMFs) enhance the cracking resistance of cement-based materials by effectively bridging cracks [6]. The specimens' roughness exhibited an upward trend with an increase in fiber volume fraction, also demonstrating a positive correlation with mechanical properties, including the peak load in tension and flexure [7]. An experimental investigation on mechanical performance, energy absorption, electrical conductivity, and piezoresistive sensibility of carbon-doped cementitious mortars [8] indicated enhancements in flexural strength, toughness, and electrical conductivity, approximately by an order of magnitude, when compared to the reference specimens. Carbon-based particles and fibers hold promise for engineering applications. In the market and across the literature, various types and shapes of carbon fillers exist, all composed of carbon atoms, varying in size from nanometric to micrometric. Common carbon inclusions for civil applications include carbon nano- and micro-fibers, carbon nanotubes, graphene, carbon black, and graphite [4; 18; 19]. In particular, these carbon-based fillers exhibit excellent mechanical and electrical capabilities for building materials, with one promising application being the enhancement of conductivity, and other electrical properties, as the self-sensing capability for structural health monitoring [20; 21]. Indeed, properly produced and tailored smart cementitious materials with carbon inclusions can monitor their state of strain and stress [22; 23]. The construction material itself, forming structures and infrastructures, can serve as a strain sensor for assessing building performance and integrity conditions. Furthermore, it can identify cracks or incipient damages caused by exceptional events or variations in usage [24; 25]. The existing literature predominantly explores cement-based matrices (such as cement pastes or mortars) and small-sized samples [26; 27; 28]. Nevertheless, the behavior of concrete smart composites and medium- to high-scale elements, together with the investigation of the tailored setup and implementation, remains largely unexplored territory,but are essential for real application of this technology [9; 29; 30]. Challenges associated with scaling this technology include ensuring the proper dispersion of fillers to achieve a homogeneous material, addressing potential adverse effects of coarse aggregates on strain sensitivity, and optimizing the type and placement of electrodes in large structures [31; 32; 33]. The literature presents works about the enhancement of fibers dispersion that could be effective for real-scale constructions, and tailored applications at higher scales could have interesting developments, [34; 35]. In light of the interest demonstrated in the literature, this paper seeks to examine the feasibility of producing cementitious cement mortar with carbon microfibers for full-scale applications in concrete structures (e.g., for local repairs) and masonry. The paper begins by describing the peculiarities of the materials and of the preparation procedures, and the tests/standards adopted for the fresh and hardened material characterization. Both rheological and mechanical tests are performed on composites with different amounts of microfibers, as presented in Section 3.