International Concrete Abstracts Portal

Service life modeling of microbially induced concrete corrosion (MICC) is essential for assessing structural durability, optimizing maintenance, and minimizing risks in wastewater environments. ASTM C1904-20 is a recently developed biogenic benchtop method for assessing MICC that is safe, accelerated, and practical compared to conventional laboratory tests. The objective of this study is to use the benchtop test to predict the service life of concrete exposed to MICC in sewer pipes. This correlation is based on the Pomeroy model that relates the field H₂S concentrations, wastewater flow conditions, pipe and flow geometry, and the properties of the concrete. A demonstration study is provided to show how the ASTM C1904 data could be used to predict the performance of different types of concrete and antimicrobial products in realistic exposure scenarios. The projected corrosion rates in field conditions reflected the delayed and reduced corrosion rates for mixtures with antimicrobial treatment.

Analysis of reinforced-concrete damage (RC) under nonuniform corrosion has mostly been performed by adopting the two-dimensional (2-D) plane strain assumption to reduce the computational efforts compared with three-dimensional (3-D) models. This paper aims to compare results obtained from the 2-D plane strain formulation with 3-D analysis in the context of nonuniform corrosion, highlighting differences and similarities to gain valuable insights into the structural response and damage prediction. The findings indicate that both the 2-D and 3-D models yield reasonably similar damage patterns with minor discrepancies in crack orientation and predict comparable hairline crack widths on the concrete surface. During initial corrosion stages, both models exhibit similar stress and strain distributions. However, as corrosion progresses, distinct variations in stress and strain patterns emerge. Interestingly, despite these differences, the extent of damage converges as corrosion advances, suggesting a critical stage beyond which the RC response remains consistent regardless of the modeling approach. The study emphasizes stress and strain variations over time for accurate RC behavior representation.

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.

In practical engineering, beams requiring strengthening were usually preloaded; research on their strengthening techniques directly affected structural safety and cost-effectiveness. This study investigated the flexural behavior of preloaded RC beams strengthened with prestressed carbon textile reinforced concrete (CTRC) plates using four-point bending tests. Parameters included preload levels and whether to unload during strengthening. Results showed that strengthening with prestressed CTRC plates effectively improved the service moment, ultimate bending moment, and crack resistance, and preload level and whether to unload during strengthening had no significant effect on the strengthening effect. All strengthened beams failed due to the CTRC plate rupturing, with post-failure moments reducing to the unstrengthened beam's ultimate moment level. Pre-cracking flexural stiffness decreased with increasing preload, and the stiffness after cracking was independent of the preload and strengthening method. Finally, the ultimate bending moments were evaluated using four current codes, with the Chinese code exhibiting the highest prediction accuracy.