A reinforcing bar coated with Fiber Reinforced Cementitious Composites (FRCC), called “coated rebar,” has possibilities of enhancing not only tensile properties but also resistance to rebar corrosion when embedded in concrete members. This study aims to investigate the bond behavior of coated rebars used in RC members. Several FRCC with different strength and ductility, including Ultra High Performance-Strain Hardening Cementitious Composite (UHP-SHCC), were used as the coating materials. Tensile tests for the coated rebars were conducted to evaluate the crack distributions of the coated bars themselves. Flexural load tests were also performed to evaluate the influences of coated rebars on crack distribution in RC beams. As a result, the experimental results demonstrated that the crack distribution of RC beams depends on the cracking ability of the coated rebar. The coated rebar with UHP-SHCC, having excellent cracking ability, shows better crack distribution in the RC beam than those with the other materials in this study.

In the 21st century, humanity faces increasing concerns about climate change and natural hazards such as earthquake earthquakes and floods that induce deaths, homelessness and economic loss due to poor performance of civil infrastructure, particularly in ODA-eligible countries like Turkey, where the majority of infrastructures are mainly made of concrete. Therefore, it is also very important to ensure infrastructural assets are free from structural damage and are made up of environmentally friendly materials with long-term durability performance. The current project explores the development and use of a novel ductile, resilient composite material, improving the safety and resilience of civil infrastructures and reducing their repair and maintenance costs. For that purposes, nano boron nitride with two-dimensional layered structure has incorporated into sustainable engineered cementitious composites (ECC) to reinforce/modify their properties and performances. Then, flexural strength, compressive strength, and ultrasonic pulse velocity experiments were conducted on the prepared composites. One of the main objectives of this project is also to provide an in-depth understanding of the cracking characteristics and fracture behaviour of the samples in the light of micro-structural analysis obtained by using Scanning Electron Microscopy (SEM), X-Ray Diffraction method, and fractal theory. The investigation into the characteristics of these damages through systematic experimental and numerical analyses, will help better tailor and design nano modified engineered cementitious composites with desirable engineering properties, which would further promote the usage of this innovative composite in structural applications.

Fiber-reinforced concrete (FRC) is widely used in structures subjected to high strain-rate loadings, such as military facilities, earthquake-resistant buildings, hydroelectric dams, and industrial and highway pavements. Despite significant advances in recent decades, certain structural behaviors remain underexplored, particularly when combining different concretes, such as thin strengthening layers with distinct characteristics, and incorporating different fibers like strain-hardening cementitious composites (SHCC) or even ultra-high-performance concrete (UHPC). Additionally, the application of carbon textiles in these strengthening layers warrants further investigation. This study aims to evaluate the impact resistance of steel fiber reinforced concrete (SFRC) short beams under flexural impact loading, with the addition of SHCC, UHPC, and UHPC layers reinforced with carbon textiles on the tensile face of the beams. The mechanical performance of the composite specimens was assessed through flexural impact tests at varying energy levels. A custom-built drop-weight testing machine, developed at the Structures and Materials Laboratory at PUC-Rio, was used for this purpose. Furthermore, Digital Image Correlation (DIC), in conjunction with high-speed cameras, was employed to measure energy absorption, deformation, and crack propagation in the beams under different configurations and impact energies. The results demonstrated that the SHCC layers significantly improved energy absorption and reduced crack formation. At the same time, the UHPC composites, particularly those reinforced with carbon textiles, exhibited enhanced ductility, energy absorption capacity, and crack control under impact loading. These findings suggest that the improved performance of these composite materials can reduce future repair and reinforcement needs for structures exposed to such demanding conditions.

This study examines the impact of microfibre inclusion on the tensile properties of cement paste at the microscale through both experimental and simulation approaches. Micro-cubes containing vertically aligned microfibres were fabricated using cement pastes with varying water-to-cement (w/c) ratios, ranging from 0.3 to 0.5. These specimens underwent a splitting test using a nano-indenter with a wedge tip, and the results were compared to those of micro-cubes without fibres. Mechanical properties, including load capacity, peak deformation, stiffness, and fracture energy, were analysed. The findings indicate that fibre inclusion reduced the splitting tensile stress and modulus of the micro-cubes across all w/c ratios. Additionally, the influence of fibre inclusion became more pronounced with higher w/c ratios, likely due to a more porous interfacial transition zone (ITZ) at these higher ratios. To complement the experimental work, a lattice model with a simplified microstructure, comprising paste, fibre, and ITZ, was developed to simulate the fracture behaviour of the micro-cube under indentation splitting. The simulation results were in strong agreement with the experimental data, facilitating the determination of the mechanical properties of the ITZ.