Vinicius Brother dos Santos

The growing demand for sustainable construction has intensified the need for advanced materials and robust assessment frameworks that integrate mechanical performance with environmental eff... Practical ApplicationsThis study provides a practical, data-driven framework to guide sustainable UHPC mix design by predicting fc and eco-efficiency indices. The predictive models enable engineers...

The use of ultra‐high‐performance fiber reinforced concrete (UHPFRC) to repair or rehabilitate old concrete structures has been shown to be appropriate due to its properties, such as higher compressive strength, ductility, and durability than conventional concretes. One of the studied strengthening techniques is the reinforced concrete columns jacketing by UHPFRC. Some recent research evaluated some parameters, such as the repair thickness and the volumetric ratio of stirrups. However, other important parameters, such as UHPFRC jacketing thickness in different column cross‐sections and the concrete core compressive strength, need to be addressed. In addition, the analytical models presented in the literature are restricted to only one concrete grade. The present study aims to evaluate the behavior of short reinforced concrete columns strengthened with UHPFRC subjected to centered compression. Numerical analyses of three‐dimensional models were performed using the finite element method, validated, and calibrated using experimental results. The influence of the concrete core compressive strength, the UHPFRC jacketing thickness, and the shape of the cross‐section were evaluated. Numerical simulations concluded that the lower concrete core compressive strength columns showed the best relative increase performance. Moreover, the concrete core strength was inversely proportional to the resistance capacity of the repair system. In addition, the increase in repair thickness contributes to the axial strength of the column. Furthermore, the cross‐section influences the distribution of stresses and strains, showing the best performance for circular sections. Finally, regardless of cross‐section type, the proposed equations accurately predicted the numerical results.

Ultra-high performance concrete (UHPC) is an appropriate material to repair and rehabilitate aged structures due to its excellent properties, such as high compressive strength and durability. Several studies have demonstrated the effectiveness of applying UHPC in old buildings as a rehabilitation or repair material, but the bond between concretes needs more investigation. In this sense, the bond between normal-strength concrete (NSC) and UHPC is currently being studied. Three main parameters are responsible for ensuring a good bond: the surface treatment of the substrate (roughness), the wetting conditions, and the mechanical strength of the substrate. Thus, the present study investigated the bond between concretes experimentally. The concrete of the substrate was carried out in three grades: C25, C45, and C60. The repair concretes were C25, C45, C60, and UHPC. The following parameters were evaluated: wetting conditions, air surface dry (ASD), saturated surface dry (SSD), substrate strength, and repair concrete strength. All models received surface treatment by wire brushing. Slant shear and splitting tensile tests were performed to evaluate the mechanical behavior and the failure modes of the bond between concretes. The bond strength was classified and compared to existing predicting models. The results showed that most expressive strength gains occurred in SSD models with lower strength substrates and UHPC. Furthermore, the influence of surface wetting conditions becomes smaller as the strength of the substrate is reduced.