International Concrete Abstracts Portal

This study presents a comprehensive review of eco-friendly materials and advanced repair techniques for rehabilitating reinforced-concrete (RC) structures, emphasizing their role in promoting sustainability and enhancing performance. By evaluating fifty-five research programs conducted between 2001 and 2024, the study focuses on emerging materials such as geopolymers, natural fibers, and fiber-reinforced composites, highlighting their mechanical properties, environmental benefits, and potential for integration into traditional RC systems. The review is thematically organized into four areas: (1) Sustainability and Environmental Impacts, (2) Material Innovation and Properties, (3) Repair Techniques and Efficiency, and (4) Structural Performance. Key findings reveal that these materials not only reduce the carbon footprint of construction but also significantly improve structural durability, corrosion resistance, and long-term performance under varying environmental conditions. Specifically, geopolymer concretes exhibit low CO₂ emissions and superior bond strength; bamboo and flax fibers offer strong tensile capacity with renewable sourcing; and MICP techniques deliver self-healing functionality that reduces dependency on chemical-based crack sealants. Additionally, the use of recycled and bio-based materials further contributes to cost-efficiency and environmental resilience, fostering circular economy principles. By synthesizing findings across these domains, this study provides practical insights into how eco-friendly materials can simultaneously address environmental, structural, and economic challenges in RC repair. The study underscores the importance of adopting innovative repair methods that incorporate these sustainable materials to address modern civil engineering challenges, balancing infrastructure longevity, sustainability, and reduced environmental impact.

This paper presents an experimental study on the residual bond of glass fiber-reinforced polymer (GFRP) rebars embedded in ultra-high-performance concrete (UHPC) subjected to elevated temperatures, including a comparison with ordinary concrete. Based on the range of thermal loading from 25°C (77°F) to 300o°C (572o°F), material and push-out tests are conducted to examine the temperature-dependent properties of the constituents and the behavior of the interface. Also performed are chemical and radiometric analyses. The average specific heat and thermal conductivity of UHPC are 12.1% and 6.1% higher than those of ordinary concrete, respectively. The temperature-induced reduction of density in these mixtures ranges between 5.4% and 6.2% at 300o°C (572o°F). Thermal damage to GFRP, in the context of microcracking, is observed after exposure to 150°C (302°F). Fourier transform infrared spectroscopy reveals prominent wavenumbers at 668 cm^-1 (263 in.^-1) and 2,360 cm^-1 (929 in.^-1), related to the bond between the fibers and resin in the rebars, while spectroradiometry characterizes the thermal degradation of GFRP through diminished reflectivity in conjunction with the peak wavelength positions of 584 nm (2,299×10^-8 in.) and 1,871 nm (7,366×10^-8 in.). The linearly ascending bond-slip response of the interface alters after reaching the maximum shear stresses, leading to gradual and abrupt declines for the ordinary concrete and UHPC, respectively. The failure mode of the ordinary concrete interface is temperature-sensitive; however, spalling in the bonded region is consistently noticed in the UHPC interface. The fracture energy of the interface with UHPC exceeds that of the interface with the ordinary concrete beyond 150o°C (302o°F). Design recommendations are provided for estimating reductions in the residual bond of the GFRP system exposed to elevated temperatures.

In performance-based seismic design, buckling and fracture of longitudinal steel in reinforced concrete columns are damage limit states that may be considered for damage control and near collapse, respectively. This study evaluates the progression of buckling instability, which eventually leads to bar fracture, based on bending strains measured in buckled bars of cyclic quasi-static column tests. Buckling-induced bending strains are calculated with bare bar fiber models and experimental buckled shapes of longitudinal reinforcement in the column data set. This study proposes an empirical equation that calculates the buckling-induced bending strain based on column displacement ductility, low-cycle fatigue, and column design parameters for grade 60 steel. This study also identifies the buckling-induced bending strains that trigger transverse steel yielding, visual bar buckling, and brittle bar fracture.

The influence of alkaline aging on the basalt fiber-reinforced polymer (BFRP) bar reinforced concrete beam has not been thoroughly investigated, and the deterioration level can be further increased in seawater sea sand concrete (SSC) due to increased alkalinity. This study aims to unveil the coupled influence mechanism of accelerated sweater aging and impact loading on the impact resilience of BFRP-SSC beams. The influence of concrete strength, reinforcement ratio, falling weight height, and accelerated aging in seawater on the impact resistance of BFRP-SSC beam is examined. The results indicate that enhancing concrete strength can more obviously increase the peak impact force than enhancing the reinforcement ratio due to the higher strain rate sensitivity. The increased falling weight energy can increase the peak impact force while reducing the residual bearing capacity. The accelerated aging in seawater can reduce the peak impact force and increase the maximum midspan displacement. And the impact failure mode of the BFRP-SSC beam can be changed from concrete crushing to BFRP bar fracture due to the bar degradation. The peak impact force of beam specimens soaked in seawater at room temperature and 55°C conditions is reduced by 13.8% and 15.5%, while the maximum midspan displacements are increased by 32.2% and 47.1%, respectively. This study can serve as a solid base for the impact design of FRP bar reinforced seawater sea-sand and concrete beams.

In this study, fabric formwork is used to cast I-shaped and non-prismatic tapered reinforced concrete (RC) beams that have up to a 40% reduction in concrete volume, resulting in lower embodied CO2 than a rectangular prismatic beam. The primary aim of this research is to use distributed sensing to characterize the behavior of these shape-modified beams to an extent that was not previously possible and compare their behavior to that of a conventional rectilinear beam. Four RC beams (a rectangular control and three fabric-formed sections) were tested in three-point bending. Distributed fiber-optic strain sensors were used to measure strains along the full length of the longitudinal reinforcement, and digital image correlation (DIC) was used to acquire crack patterns and widths. The results indicate that fabric-formed RC beams can achieve the same load-carrying capacity as conventional rectilinear prismatic beams and meet serviceability requirements in terms of crack widths and deflections. The longitudinal reinforcement strains along the full length of the specimens were captured by Canadian concrete design equations, which account for the effects of both flexure and shear on reinforcement demand.