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.

Additive construction augments the laborious construction of structural concrete; however, its implementation remains mostly limited to building envelopes. Culvert construction benefits from alternative methods due to the high demand for transportation infrastructure. In this study, extrusion-based 3-D concrete printing (3DCP) is developed for the first time for culvert construction. Large-scale unreinforced concrete pipes were printed, and the early-stage (e.g., buildability), mechanical, and durability properties of two commercially available 3DCP materials were determined. Additionally, the specimens were tested structurally and exceeded the expected structural performance (by about an average of 32%) under the three-edge bearing test. However, the desired durability was not met due to the porosity of the specimens. The mix design with microfibers exhibited marginally higher compressive and tensile strength, but did not meet durability criteria similar to non-fiber material. Results indicated the 3DCP feasibility for pipe culvert construction and mapped further direction for widespread implementation and addressing concrete pipe durability issues.

Engineered cementitious composite (ECC), a prominent innovation in the realm of concrete materials in recent years, contains a substantial amount of cement in its composition, thereby resulting in a significant environmental impact. To enhance the environmental sustainability of ECC, it is plausible to substitute a large portion of cement in the composition with fly ash, a by-product of coal-fired power plants. Recent years have seen increased research in ECC containing high-volume fly ash (HVFA) binder and its wider application in construction practices. In this particular context, it becomes imperative to review the role of HVFA binder in ECC. This review first examines the effects of incorporating HVFA binder in ECC on the fiber dispersion and fiber-matrix interface behavior. Additionally, mechanical properties, including compressive strength, tensile behavior, and cracking behavior under loading, as well as durability performances of HVFA-based ECC under various exposure conditions, are explored. Last, this review summarizes the research needs pertaining to HVFA-based ECC, proving valuable guidance for future endeavors in this field.

Engineered cementitious composites (ECC) represent a significantinnovation in construction materials due to their exceptionalflexibility, tensile strength, and durability, surpassing traditionalconcrete. This review systematically examines the composition,mechanical behavior, and real-world applications of ECC, with afocus on how fiber reinforcement, mineral additives, and micromechanical design improve its structural performances. The present study reports on the effects of various factors, including different types of mineral admixtures, aggregate sizes, fiber hybridization, and specimen dimensions. Key topics include ECC’s strain hardening properties, its sustainability, and its capacity to resist crack development, making it ideal for high-performance infrastructure projects. Additionally, the review discusses recentadvancements in ECC technology such as hybrid fiber reinforcementand the material’s growing use in seismic structures. The paper also addresses the primary obstacles, including high initial costs and the absence of standardized specifications, while proposing future research paths aimed at optimizing ECC’s efficiency and economic viability.

Noncorrosive fiber-reinforced polymer (FRP) reinforcement presents an attractive alternative to conventional steel reinforcement, which is prone to corrosion, especially in harsh environments exposed to deicing salt or seawater. However, FRP reinforcing bars’ lower axial stiffness leads to greater crack widths when FRP reinforcing bars elongate, resulting in significantly lower flexural stiffness for FRP bar-reinforced concrete members. The deeper cracks and larger crack widths also reduce the depth of the compression zone. Consequently, both the aggregate interlock and the compression zone for shear resistance are significantly reduced. Additionally, due to their limited tensile ductility, FRP reinforcing bars can rupture before the concrete crushes, potentially resulting in sudden and catastrophic member failure. Therefore, ACI Committee 440 states that through a compression-controlled design, FRP reinforced concrete members can be intentionally designed to fail by allowing the concrete to crush before the FRP reinforcing bars rupture. However, this design approach does not yield an equivalent ductile behavior when compared to steel-reinforced concrete members, resulting in a lower strength reduction, ϕ, value of 0.65. In this regard, using FRP-reinforced ultra-high-performance concrete (UHPC) members offer a novel solution, providing high strength, stiffness, ductility, and corrosion-resistant characteristics. UHPC has a very low water-cementitious materials ratio (0.18 to 0.25), which results in dense particle packing. This very dense microstructure and low water ratio not only improves compressive strength but delays liquid ingress. UHPC can be tailored to achieve exceptional compressive ductility, with a maximum usable compressive strain greater than 0.015. Unlike conventional designs where ductility is provided by steel reinforcing bars, UHPC can be used to achieve the required ductility for a flexural member, allowing FRP reinforcing bars to be designed to stay elastic. The high member ductility also justifies the use of a higher strength reduction factor, ϕ, of 0.9. This research, validated through large-scale experiments, explores this design concept by leveraging UHPC’s high compressive ductility, cracking resistance, and shear strength, along with a high quantity of noncorrosive FRP reinforcing bars. The increased amount of longitudinal reinforcement helps maintain the flexural stiffness (controlling deflection under service loads), bond strength, and shear strength of the members. Furthermore, the damage resistant capability of UHPC and the elasticity of FRP reinforcing bars provide a structural member with a restoring force, leading to reduced residual deflection and enhanced resilience.