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.

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.

focused on the impacts of geometric design parameters on the structural performance of drilled shaft footings. Large-scale tests were conducted on specimens subjected to uniform column compression and constructed with different geometric conditions permitting the examination of varied strut inclination, shaft diameter, and footing depth. The experimental results obtained confirmed that footing strength was highly dependent on strut inclination while shaft diameter affected the ultimate damage pattern. Strength calculations based on three-dimensional (3-D) strut-and-tie modeling guidelines recently developed by the authors provided less conservative results as compared to previous recommendations and resulted in levels of accuracy consistent with those of other shear design procedures adopted in code provisions.

This study addressed a critical knowledge gap by examining the influence of staggering on the bond strength of lapped glass fiber-reinforced polymer (GFRP) bars in concrete members. It involved a comprehensive investigation of new-generation GFRP bars with varying staggering configurations in nine large-scale GFRP-reinforced concrete (RC) beams with a rectangular cross section of 300 x 450 mm (11.8 x 17.7 in.) and a length of 5200 mm (204.7 in.). The tests investigated splice strength with three staggering distances: 0, 1.0, and 1.3 times the splice length (ls) from center-to-center of two adjacent splices, and three splice lengths of 28, 38, and 45 times the bar diameter (db). Results revealed a slight improvement in ultimate load-carrying capacity (less than 10%) for partially and fully staggered splices compared to non-staggered ones, with the latter exhibiting a more ductile failure mode. The effect of staggering was consistent across different splice lengths, demonstrating that splice length was not a factor. Although staggering reduced flexural crack width, it increased the total number of cracks due to expanded splice regions. Bond strength improved with staggering, with gains of 4.0% and 8.0% for partially and fully staggered splices, respectively. ACI CODE- 440.11-22 provides more accurate predictions of the bond strength of lap-spliced GFRP bars than the other design codes, showing an average test-to-prediction ratio of 1.03 for non-staggered splices. Nevertheless, it requires some reconsiderations when it comes to staggered splices. To address this, a proposed modification factor was introduced to account for staggering conditions when calculating bond strength and splice length in ACI CODE-440.11-22.

Extensive experimental verification has shown that the use of fiber-reinforced polymer (FRP) anchors in combination with externally bonded FRP composites increases the flexural capacity of existing reinforced concrete (RC) structures. Thus, a rational prediction model is introduced in this study so that fiber splay anchors may be accurately designed for practical strengthening applications. Simplified structural mechanics principles are used to build this model for capacity prediction of a group of fiber splay anchors used for FRP flexural strengthening. Three existing test series using fiber splay anchors to secure FRP-strengthened T-beams, block-scale, and one-way slabs were used to calibrate and verify the accuracy and applicability of the present model. The present model is shown to yield very accurate predictions when compared to the results of the block-scale specimen and eight different one-way slabs. The proposed model is also compared with the predictions of a design equation adapted from the case of channel shear connectors in composite concrete-steel construction. Results show a very promising correlation.