International Concrete Abstracts Portal

Despite the advantageous features of earthen construction for sustainability, certain limitations arise, notably the time-intensive nature of the construction process. Some efforts have been made to achieve self-consolidating earth concrete (SCEC) by overcoming the presence of fine particles to achieve adequate rheology. The impacts of cement, metakaolin, and limestone filler on dry flowability characteristics, rheology, workability, and compressive strength of self-consolidating earth paste (SCEP) mixtures were assessed in this study. The investigated mixtures were proportioned with different clay compositions and polycarboxylate ether (PCE), with and without the initial addition of sodium hexametaphosphate (NaHMP) as a clay dispersant. It was revealed that the addition of NaHMP and metakaolin to the mixtures consisting of finer clay particles significantly increased the static yield stress, build-up index, critical shear strain, and storage modulus evolution. Finally, the contribution of dry flowability characteristics of the powders to the rheological properties of the SCEP mixtures was investigated to facilitate the selection process.

This study focuses on enhancing the durability of two-component grouting materials by incorporating ground-granulated blast- furnace slag (GGBFS) and replacing cement with industrial waste to reduce environmental pollution. A ternary cementitious system was developed using 30% GGBFS and 10% carbide slag (CS) as partial cement replacements. The research investigates the effects of different water-bentonite ratios, water-binder ratios (w/b), and A/B component volume ratios on the physical and mechanical properties of the grout, including density, fluidity, bleeding rate, setting time, and strength performance. The microstructural evolution and hydration products were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and thermogravimetric analysis (TGA). The findings provide insights for optimizing the mixture design of grouting materials in shield-tunneling applications, with a focus on improving performance and sustainability.

The use of recycled plastic aggregate in cement-based materials has emerged as a promising strategy to reduce plastic waste and promote sustainable construction. However, the inherent hydrophobicity of plastic surfaces poses a significant challenge by limiting their bonding with the cement matrix. This review critically examines five major surface treatment methods, such as coating, oxidation, silane, plasma, and radiation, to enhance the compatibility of recycled plastic aggregates in cementitious composites. Coating with materials such as waterglass, slag powder, or acrylic resins improved compressive strength by up to 78% depending on the coating type. Oxidation using hydrogen peroxide or calcium hypochlorite increased hydrophilicity and improved strength by approximately 10%–30%, while excessive treatment with NaOH-hypochlorite mixtures reduced strength by up to 60%. Silane treatment significantly enhanced surface bonding, resulting in improved mechanical properties. Plasma treatment demonstrated high efficiency, reducing contact angles from ~108° to 44.0° within 30 seconds. Radiation treatment using gamma rays and microwaves increased surface roughness and strength, with gamma irradiation at 100–200 kGy leading to substantial improvements in compressive strength and surface morphology. To the authors’ knowledge, this is the first review to systematically compare the effectiveness, mechanisms, and limitations of these surface treatments specifically for recycled plastic aggregates in cement-based materials. This review also highlights the practical challenges of scaling such treatments, including energy demand, chemical handling, and cost, and identifies future directions such as bio-based coatings and nanomaterial functionalization. The findings provide critical insight into optimizing surface treatments to improve the mechanical performance, durability, and sustainability of concrete incorporating plastic aggregates, supporting their broader adoption in sustainable construction practices.

The durability of reinforced concrete is often compromised by chloride penetration, leading to corrosion of reinforcing steel and reduced structural strength. To improve the sustainability and longevity of concrete structures, it is crucial to model and predict chloride permeability (CP) accurately, thereby minimizing the time and resources required for extensive experimental testing. This paper presents a proof-of-concept study applying Artificial Neural Networks (ANN) to predict CP in concrete structures. The model was trained on a small but carefully controlled experimental dataset of 10 concrete mixtures, considering four key parameters: water-to-cementing materials ratio, silica fume content, cementing materials content, and air content. Despite the limited dataset size, which constrains generalizability and statistical robustness, the ANN captured nonlinear relationships among the input parameters and CP. The comparison between experimental and simulated CP values showed reasonable agreement, with errors ranging between –242 and 420 Coulombs. These results establish the trustworthiness and reliability of the proposed model, providing a valuable tool for predicting CP and informing the design of durable and sustainable concrete structures.

CO2 mineralization in concrete enhances cement hydration by reacting with calcium-rich materials, forming nano-scale calcium carbonate that fills micro-pores. This study explores CO2-mineralized concrete performance, produced using a two-step mineralization process. Concrete with 0.2% CO2 by cement weight exhibited significantly higher compressive strength, increasing by 18.78%, 19.27%, and 20.63% at 7, 28, and 56 days, respectively. Isothermal calorimetric analysis confirmed increased heat evolution in CO2-mineralized cement paste, while X-ray diffraction and scanning electron microscopy revealed calcium carbonate formation and more ettringite volume. The higher strength gain due to CO2 mineralization is used to leverage the cement content. A comparative study reveals that CO2-mineralized concrete with 7.5% reduced cement content achieves equivalent strength and durability to conventional concrete, reducing carbon emissions by 8% while significantly lowering cost per unit strength and enhancing sustainability and performance.