International Concrete Abstracts Portal

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.

The weakness of concrete in tension can be mitigated by developing fiber-reinforced concrete (FRC) to induce pseudoductility. However, enhancing the intrinsic tensile strength of the matrix in FRC has received little attention. In this regard, nanofibers, which can improve the intrinsic tensile properties of the matrix, were used in conjunction with microfibers to enhance intrinsic tensile strength. Different volumes of nanofibers (0.0 to 0.6%) and microfibers (0.0 to 2.0%) were tested, and various fresh and hardened properties were analyzed. Test results show that the high-range water-reducing admixture dosage increased with both nanofiber and microfiber volume and that strength increased with microfiber volume, reaching an optimum point at a certain nanofiber dosage. Moreover, incorporating nanofibers and microfibers to develop multiscale FRC (MSFRC) significantly improved direct tensile strength and energy absorption. The synergy between nanofibers and microfibers was revealed both qualitatively and quantitatively, contributing to the advancement of FRC.

This study investigates the impact of air-entraining admixtures (AEAs) on mortar performance, focusing on fresh-state and hardened-state properties critical to durability and engineering applications. Ten distinct mortar mixtures were analyzed, following guidelines established by the European Federation of National Associations Representing Producers and Applicators of Specialist Building Products for Concrete (EFNARC). AEAs were introduced at varying proportions (0.01 to 0.5% of cement weight) to evaluate their effects on intrinsic properties (density, void ratio, and water absorption), rheological parameters (plastic viscosity and yield stress), and mechanical characteristics (compressive strength, ultrasonic velocity, and modulus of elasticity). Regression models were developed and yielded high predictive accuracy, with R2 values exceeding 0.98. Notably, ultrasonic velocity and modulus of elasticity demonstrated strong correlations with intrinsic properties across all curing ages. Similarly, compressive strength showed significant associations with rheological parameters, highlighting the influence of air content and flow behavior on structural performance. These findings offer precise quantitative models for predicting mortar behavior and optimizing formulations for enhanced performance.

The applications of alkali-activated slag (AAS) face challenges such as poor workability, rapid setting, and high autogenous shrinkage, which require chemical admixtures (CAs) to adjust the performance of AAS. Unfortunately, there are limited specific CAs available to tune AAS properties. To address this gap, this study proposes using a ubiquitous, naturally occurring compound, L-ascorbic acid (LAA), as a multifunctional performanceenhancing additive for AAS to overcome the major challenges of AAS. The findings showed that LAA can function as a retarder, plasticizer, strength enhancer, and autogenous shrinkage reducer for AAS. When 0.5% LAA was added, the compressive strengths of AAS mortars at 3 and 28 days increased by 28.9% and 19.6%, respectively, and the 28-day autogenous shrinkage decreased by 43.1%. Both surface adsorption and ion complexation have been confirmed as the working mechanisms of LAA in hydrated AAS.

In this paper, uniaxial tensile testing of semi-grouted sleeve connectors was carried out by controlling the amount of expansive agent in the grout material. The effects of different steel bar diameters and anchorage depths on the failure mode, bearing capacity, and surface strain of sleeve connectors were studied. It is found that there are three failure modes in the specimens—namely, steel bar pullout failure, steel bar slip failure, and screw thread failure. The expansion characteristics of the grout material can partially compensate for the lack of compressive strength. Based on the analysis of the ultimate bearing capacity of different specimens, a design method to prevent the slip failure of the semi-grouted sleeve is proposed. The addition of 5 to 11% expansive admixture can reduce the circumferential strain of the casing from the steel bar anchorage location to the grouting end by 28.57 to 125.30%, with no impact on the longitudinal strain variation pattern. As the depth of steel bar anchorage increases, the expansive effect of the steel bar anchorage and casing longitudinal strain gradually surpasses the shrinkage effect, while the shrinkage effect at the grouting end of the casing gradually outweighs the expansive effect. With an increase in steel bar diameter, the longitudinal strain at the grouting end of the casing only decreases by 1.75% and 2.10%, essentially having no significant impact.