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.

The production of carbonated aggregates from Class F fly ash (FA) is challenging due to its low calcium content, typically less than 10%. This study investigates the production of carbonated alkali-activated aggregates using FA and calcium carbide sludge (CCS). Sodium hydroxide was used as an activator and examined the effects of autoclave treatment on the properties of these aggregates. The optimal mixture, comprising 70% FA and 30% CCS, achieved a single aggregate strength of >5 MPa in autoclave carbonated (AC) aggregates, comparable to the strength obtained after 14 days of water curing in without autoclave carbonated (WAC) aggregates. Both AC and WAC aggregates exhibited a bulk density of 790 to 805 kg/m³ and CO₂ uptake of 12.5% and 13.3% in AC and WAC aggregates, respectively. FE-SEM and FT-IR analysis indicated the formation C-A-S-H gel in noncarbonated aggregates, while calcite and vaterite, along with N-A-S-H gel, formed in carbonated aggregate. Concrete incorporating AC and WAC aggregates exhibit compressive strengths of 39 and 38 MPa, with concrete density of 2065 kg/m³ and 2085 kg/m³, respectively. Furthermore, AC and WAC aggregate concrete showed a reduction in CO₂ emission of 18% and 31%, respectively, compared to autoclave noncarbonate (ANC) aggregate concrete. These findings highlight the potential of producing carbonated alkali-activated aggregates from FA and CCS as sustainable materials for construction applications.

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.

Prolonged neutron irradiation can damage concrete biological shields, particularly when nuclear power plants extend reactor lifespans. Retrofitting biological shields with thin and highly efficient neutron shields may limit neutron damage. Portland cement mortars amended with boron carbide and polyethylene powders were assessed for neutron attenuation. Shielding performance was compared to concrete with a similar design and coarse aggregate as a biological shield at an operational nuclear plant. Boron carbide enhanced the shielding performance of specimens under the full energy spectrum of the neutron source. Boron carbide and polyethylene synergistically enhanced neutron attenuation under a purely high-energy neutron flux. Engineered thin composite mortars needed 90% less thickness to achieve similar or better shielding efficiency as the concrete in a typical biological shield under the test conditions. Isothermal calorimetry, compressive strength, and thermal expansion results indicate that mixture design parameters of thin shields can be adjusted to achieve adequate structural properties without diminishing constructability or structural performance.

This research establishes a systematic methodology for selecting a migratory corrosion inhibitor (M-CoI) as a repair strategy for reinforced concrete structures exposed to aggressive environments. Conducted in two phases, Phase 1 involves corrosion testing in pore solutions to evaluate inhibitor efficacy, while Phase 2 examines the percolation ability of M-CoIs in different concrete systems and the performance of M-CoI in RC with corroded reinforcing bars. The findings reveal that the efficiency of the compounds as repair measures is significantly lower than their preventive performance, primarily due to the presence of corrosion products on the steel surface. Additionally, the effectiveness of the M-CoIs is influenced by their concentration and form at the reinforcing bar level; specifically, 4-Aminobenzoic acid (ABA) achieved maximum concentration in its purest form, whereas Salicylaldehyde (SA) and 2-Aminopyridine (AP) reached the reinforcing bar in lower concentrations. Importantly, the study highlights that compounds effective in pore solution may not perform well in concrete, underscoring the necessity of considering the intended application, preventive or repair, when selecting inhibitors. Thus, a comprehensive approach involving both pore solution testing and migration ability assessments is essential for optimal corrosion protection in reinforced concrete.