International Concrete Abstracts Portal

In this work, novel polycarboxylate admixtures were synthesized by two different free radical polymerization systems of methacrylic acid (MAA) and methoxy polyethylene glycol methacrylate (MPEG-MA) for PC-1, and acrylic acid (AA) and iso amyl alcohol polyethylene glycol (IAA-PEG) for PC-2. Thioglycolic acid as a chain transfer agent and ammonium persulphate as an initiator were used. The synthesized carboxylic polymers were characterized using FTIR, H-NMR, gel permeation chromatography (GPC), and thermogravimetric analysis (TGA). The influence of the chemical structure of polycarboxylates on the rheology of the concrete, as well as the prognosis of the superplasticizer’s development, is also presented through measuring water consistency, setting times, flow table, slump test, Zeta potential, and compressive strength. The cementitious products were investigated with X-ray diffraction (XRD) and scanning electron microscope (SEM). The developed superplasticizers have shown good dispersion effects and slump performance in workability and fluidity retention tests, adsorption performance, and scanning electron microscopy performance. Intriguingly, the PC-1 and PC-2 mixes achieved flow table values of 230 and 200 mm, respectively. The compressive strength values at various curing ages up to 28 days exhibited double and triple values compared with the control sample. Additionally, compared to the control ordinary Portland cement paste, a reduction of water-to-cement ratio of about 0.25 and the development of excessive hydration products give PC-1 and PC-2 extensive pastes a more dense and compact structure in XRD and SEM investigation.

This study examines the lateral cyclic response of a repaired damaged bridge pier originally reinforced with fiber-reinforced polymer (FRP) bars, particularly glass FRP (GFRP), as a corrosion-resistant and durable alternative to traditional steel. An as-built large-scale hybrid (GFRP-steel) reinforced concrete (RC) column had an outer cage reinforced with GFRP bars and an inner cage reinforced with steel reinforcing bars. The columns were first tested under cyclic lateral loading, where the hybrid specimen demonstrated ductility and energy dissipation capacity comparable to the conventional single-layer steel RC column. Following these initial tests, both specimens were repaired using FRP wraps and retested under the same loading protocol, resulting in a total of four tests. Enhanced structural integrity and energy dissipation demonstrate the effectiveness of innovative repair techniques in seismic engineering. These findings provide a blueprint for resilient infrastructure in earthquake-prone areas and contribute to advancements in bridge design and repair strategies.

This paper presents the interface shear between ordinary concrete and ultra-high-performance concrete (UHPC) connected with glass fiber-reinforced polymer (GFRP) reinforcing bars. Following ancillary tests on reinforcing bar fracture under in-plane shear loading, concrete-reinforcing bar assemblies are loaded to examine capacities and failure modes as influenced by the size, spacing, and number of the reinforcing bars. While the shear behavior of bare reinforcing bars is primarily governed by the orientation of the load-resisting axes in the glass fibers and their volume, the size and spacing of the reinforcement largely control the interface capacity by affecting the load-transfer mechanism from the reinforcing bar to the concrete. The degree of stress distribution affects the load-displacement response of the interface, which is characterized in terms of quasi-steady, kinetic, and failure regions. The primary failure modes of the interface comprise rebar rupture and concrete splitting. The formation of cracks between the ordinary concrete and UHPC results from interfacial deformations, leading to spalling damage when applied loads exceed service levels. An analytical model is formulated alongside an optimization technique. The capacities of the interface in relation to the reinforcing bar rupture and concrete splitting failure modes are predicted. Furthermore, a machine learning algorithm is used to define a failure envelope and propose practice guidelines through parametric investigations.

This paper presents the behavior of anchorage zones, also known as end zones, with discrete reinforcing bars and continuous meshes. To examine the implications of various reinforcing schemes on the capacity, cracking, and failure of end zones, 50 block specimens are loaded, and their responses are analyzed. Test parameters include the types of reinforcing bar materials (steel and glass fiber-reinforced polymer, (GFRP)) and the configurations of the reinforcing bars and steel meshes (single and multiple placements). In terms of load-carrying capacity, the specimens embedded with the GFRP rebars outperform those with the steel reinforcing bars and meshes by 14.0%. The post-peak load drop of the blocks with the steel and GFRP reinforcing bars is analogous due to distributed axial stresses in the unreinforced concrete region, differing from the abrupt drop observed in the specimens with the steel meshes that intersect the concrete in orthogonal directions. While concrete splitting originates from local tension generated near the axial compression, the location of cracking is dominated by the path of stress trajectories related to the number of reinforcing bars, which is not recognized in the case of the meshed specimens. The pattern of the isostatic lines of compression clarifies the development of bursting forces that cause cracking in the concrete. A two-stage analytical model is formulated to predict the magnitude of bursting forces and determine the effects of several parameters on the response of the end zones. The applicability of existing design expressions is assessed, and the need for follow-up research is delineated.

This study investigated the shear bond behavior, with and without optimized interfaces, between conventional and geopolymer steel fiber–reinforced concretes. Sixteen prismatic and eight cylindrical composite specimens were cast with interface inclination angles of 45° and 27°, respectively. In prisms, the inclined interface area was varied: eight were optimized by 50% to balance compressive and shear stresses, allowing a more accurate determination of cohesion and friction coefficients under steel fiber effects. Fiber volume fractions of 0.0, 0.5, 1.0, and 1.5% were tested, and the influence of epoxy at the interface was also assessed. Optimized prisms exhibited adhesive failure along the interface, matching the internal friction angle, whereas non-optimized prisms showed cohesive failure with a friction angle deviating from the interface. Increasing fiber content improved performance, especially when combined with epoxy. A new bond shear strength model is proposed, incorporating friction, cohesion, and fiber effects.