International Concrete Abstracts Portal

A capsule phase change material (CPCM) was synthesized using n-tetradecane as the core, expanded graphite as the shell, and ethyl cellulose as the coating material through a controlled assembly process. The results demonstrate that the infiltration of n-tetradecane significantly enhances the density of the expanded graphite, while the ethyl cellulose coating effectively prevents the desorption and leakage of the liquid phase change material during phase transitions. As a result, the CPCM exhibits a compact structure, chemical stability, and excellent thermal stability. The incorporation of this CPCM into cement-based materials endows the material with an autonomous heat-release capability at temperatures below 5°C. When the CPCM content reaches 20%, the thermal conductivity of the cementitious matrix increases by 24.66%. Moreover, the CPCM significantly improves the freeze-thaw resistance of the cement-based materials, reducing the compressive strength loss by 96% and the flexural strength loss by 65% after freeze-thaw cycles. This CPCM fundamentally enhances the frost resistance of cement-based materials, addressing the issue of freeze-thaw damage in concrete structures in cold regions.

Engineered cementitious composites (ECC) represent a significant innovation in construction materials due to their exceptional flexibility, tensile strength, and durability, surpassing traditional concrete. This review systematically examines the composition, mechanical behaviour, and real-world applications of ECC, with a focus on how fiber reinforcement, mineral additives, and micromechanical design improve its structural performance. 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 recent advancements in ECC technology, such as hybrid fibre reinforcement and 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.

Engineered cementitious composites (ECC), a prominent innovation in the realm of concrete materials in recent years, contain a substantial amount of cement in their 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. In recent years, there has been increased research in ECC containing high-volume fly ash (HVFA) binders and its wider application in construction practices. In this particular context, it becomes imperative to review the role of the HVFA binder in ECC. This review first examines the effects of incorporating an HVFA binder in ECC on fiber dispersion and fiber/matrix interface behavior. Additionally, mechanical properties, including the compressive strength, tensile behavior, and cracking behavior under loading, as well as durability performances of HVFA-based ECC under various exposure conditions, are explored. At last, the review summarizes the research needs pertaining to HVFA-based ECC, providing valuable guidance for future endeavors in this field.

Slag-based zero-cement concrete (ZC) of high strength (60 MPa [8.70 ksi]) was developed as an eco-friendly construction material. In the present study, to investigate the structural behavior of precast columns using ZC, cyclic loading tests were performed for five column specimens with reinforcement details of ordinary moment frames. Longitudinal reinforcement was connected by sleeve splices at the precast column–footing joint. The test parameters included the concrete type (Portland cement-based normal concrete [NC] vs. ZC), construction method (monolithic vs. precast), longitudinal reinforcement ratio, and sleeve size. The test results showed that the structural performance (failure mode, strength, stiffness, energy dissipation, and deformation capacity) of the precast ZC columns was comparable to that of the monolithic NC and precast NC columns, and the tested strengths agreed with the nominal strengths calculated by ACI 318-19. These results indicate that current design codes for cementitious materials and sleeve splice of longitudinal reinforcement are applicable to the design of precast ZC columns.

Geopolymer, an inorganic polymer material, has recently gained attention as an eco-friendly alternative to Portland cement. Numerous studies have explored the potential of geopolymer as a primary structural material. This study aimed to examine the efficacy of geopolymer composites as repairing and strengthening materials rather than as structural materials. We collected and analyzed data from 782 bond strength tests and 164 structural tests including those on beams, beam-column connections, and walls. The analysis focused on critical factors affecting the bond strength of geopolymer composites with conventional cementitious concrete, and the structural behaviors of reinforced concrete members repaired or strengthened with these composites. Our findings highlight the potential of geopolymer composites for enhancing the resilience and toughness of existing damaged or undamaged concrete structures. Additionally, they offer valuable insights into the key considerations for using geopolymer composites as repair or strengthening materials, providing a useful reference for future research in this field.