International Concrete Abstracts Portal

Infilled cementitious composite (ICC) is produced by infilling cementitious paste into a designed aggregate skeleton. This approach enables the incorporation of both coarse aggregate and fibers while maintaining adequate fresh and hardened performance at minimal paste volume. In this study, ultra-high-performance concrete (UHPC) pastes incorporating supplementary cementitious materials were infilled into fiber-aggregate skeletons (FAS) with macro steel fiber volumes ranging from 0 to 2.0%, yielding a total of 16 ICC mixtures. The FAS packing density, UHPC infilling ability, and the fresh, mechanical, and microstructural properties of both UHPC paste and the resulting ICC were evaluated. The 28-day compressive strength of ICC ranged from 96.0 (13.9 ksi) to 121.6 MPa (17.6 ksi), while the first-cracking flexural strength increased by up to 61.8% at a fiber volume of 2.0%. The cement content of ICC ranged from 229 to 1116 kg/m3 (14.3 to 69.7 lb/ft3). Relative to the corresponding conventional UHPFRC without coarse aggregate, ICC reduced material cost by up to 50% and embodied CO2 by up to 55%. These findings demonstrate that ICC can provide a low-carbon, material-efficient pathway for sustainable structural concrete.

Concentrated shear deformation near the base of a wall, referred to herein as sliding shear, is one of the major mechanisms that can limit the strength and deformation capacity of reinforced concrete (RC) low-rise or squat walls. This paper reports tests of five large-scale RC squat wall specimens without axial load to investigate the effects of: 1) longitudinal reinforcement layout; 2) shear stress demand; 3) high-strength materials; and 4) aspect ratio (hw/lw) on the sliding shear behavior of squat walls. All specimens were tested under lateral displacement reversals. Test results indicate that the maximum strength of all test specimens with an aspect ratio of 0.5 was primarily associated with, or limited by, sliding shear at the wall base. For specimens with an aspect ratio of 0.5 and negligible axial load, the presence of special boundary elements did not have an apparent influence on wall behavior. Increasing the amount of longitudinal reinforcement, which also increased wall strength, resulted in less sliding deformation before 1.0% drift ratio. Beyond 1.0% drift ratio, all specimens with an aspect ratio of 0.5 exhibited a substantial pinching of the hysteretic response, where sliding along the wall base accounted for approximately 80% of the overall deformation. The specimen with high-strength materials exhibited less deformation capacity than other specimens due to bar fracture at the wall base. As the aspect ratio increased to 1.0, the relative contribution of sliding deformation to overall drift decreased substantially to less than 20% of the overall deformation. Based on the response characteristics of the test specimens, a sliding shear strength model for walls with negligible axial load is proposed. A database consisting of test results from 55 specimens (including five from this study) was developed to verify the proposed strength model.

The two-way shear equation in ACI CODE-440.11 was originally developed nearly two decades ago using experimental data from early fiber-reinforced polymer (FRP) materials, most of which are no longer representative of modern glass fiber-reinforced polymer (GFRP) reinforcement. With current GFRP bars exhibiting significantly improved mechanical and surface properties, the validity of the existing equation requires reassessment to ensure practical and economical design. This study evaluates the ACI CODE-440.11 two-way shear provisions using a comprehensive database of 49 GFRP-reinforced concrete (GFRP-RC) interior slabs and 14 edge column connections. The current code equation was found to be highly conservative, yielding an average test-to-predicted ratio of 2.13. Updated equations are proposed for both interior and edge conditions, reducing the ratio to 1.02 and 1.04, respectively, while maintaining acceptable statistical variation. Additionally, symbolic regression (SR) is used to develop machine-learning-based expressions that show high predictive accuracy. The proposed models provide reliable, physically grounded, and less-conservative predictions of punching shear capacity, supporting broader implementation of GFRP reinforcement in structural concrete applications.

This paper highlights the role that parameters such as pavement length, concrete confinement, concrete base/soil interface friction, and crack size have on the load capacity of unreinforced pavements. It provides a model that can be used to address these variables, which are not fully addressed by current models or testing at present. The research to date has been primarily focused on plain (unreinforced), non-ductile pavement slabs, but can be extended to reinforced slab systems using steel fiber, macrofiber, steel reinforcing bars, and steel wire mesh materials.

This study investigated the effects of sodium polyacrylate (PAAS) particle size and dosage on the workability, strength, and hydration of cementitious materials. The backscattered electron banding (BSE) was used to quantitatively analyze the degree of hydration of cement around PAAS voids under varying humidity levels. The results indicated that mortar fluidity, compressive strength, and flexural strength gradually decreased with increasing PAAS particle size and dosage. The incorporation of fine PAAS particles (45–50 μm) enhanced mechanical strength. While PAAS does not alter hydration product types, it promotes calcium carbonate formation, with calcium hydroxide, calcite, and C3S remaining dominant. Furthermore, it was found that higher humidity conditions and larger particle size PAAS particles can reduce the amount of unhydrated cement in the area around PAAS voids.