International Concrete Abstracts Portal

The durability of reinforced concrete is often compromised by chloride penetration, leading to corrosion of reinforcing steel and reduced structural strength. To improve the sustainability and longevity of concrete structures, it is crucial to model and predict chloride permeability (CP) accurately, thereby minimizing the time and resources required for extensive experimental testing. This paper presents a proof-of-concept study applying Artificial Neural Networks (ANN) to predict CP in concrete structures. The model was trained on a small but carefully controlled experimental dataset of 10 concrete mixtures, considering four key parameters: water-to-cementing materials ratio, silica fume content, cementing materials content, and air content. Despite the limited dataset size, which constrains generalizability and statistical robustness, the ANN captured nonlinear relationships among the input parameters and CP. The comparison between experimental and simulated CP values showed reasonable agreement, with errors ranging between –242 and 420 Coulombs. These results establish the trustworthiness and reliability of the proposed model, providing a valuable tool for predicting CP and informing the design of durable and sustainable concrete structures.

Building resilient infrastructure in chloride-rich environments presents significant challenges. This study examines the impact of nanosilica (NS) and ground granulated blast furnace slag (GGBFS) on chloride ingress in cement composites exposed to seawater, NaCl solution, and a combined NaCl-Na₂SO₄ solution. Analysis using microcharacterisation, BSE-EDS hypermaps, and thermodynamic modelling reveals that GGBFS enhances chloride binding by forming Friedel's salt (FSS) across all environments, effectively immobilizing chloride ions. NS further refines the cement matrix by densifying the calcium silicate hydrate (C-S-H) structure and generating additional C-S-H gels, improving physical chloride binding. This combined effect reduces porosity and strengthens resistance to chloride diffusion. Sulfate ions significantly influence hydration products and chloride binding, with excessive sulfate reducing FSS formation, thereby weakening chloride resistance. Sulfate may also convert FSS into monosulphate (AFm) and ettringite (AFt), altering chloride immobilization. Cement composites containing both GGBFS and NS demonstrated superior resistance to chloride and sulfate exposure, as confirmed by thermodynamic modelling. These findings provide insights into sulfate-chloride interactions and offer guidance for developing durable cementitious materials in aggressive environments.

The influence of alkaline aging on the basalt fiber-reinforced polymer (BFRP) bar reinforced concrete beam has not been thoroughly investigated, and the deterioration level can be further increased in seawater sea sand concrete (SSC) due to increased alkalinity. This study aims to unveil the coupled influence mechanism of accelerated sweater aging and impact loading on the impact resilience of BFRP-SSC beams. The influence of concrete strength, reinforcement ratio, falling weight height, and accelerated aging in seawater on the impact resistance of BFRP-SSC beam is examined. The results indicate that enhancing concrete strength can more obviously increase the peak impact force than enhancing the reinforcement ratio due to the higher strain rate sensitivity. The increased falling weight energy can increase the peak impact force while reducing the residual bearing capacity. The accelerated aging in seawater can reduce the peak impact force and increase the maximum midspan displacement. And the impact failure mode of the BFRP-SSC beam can be changed from concrete crushing to BFRP bar fracture due to the bar degradation. The peak impact force of beam specimens soaked in seawater at room temperature and 55°C conditions is reduced by 13.8% and 15.5%, while the maximum midspan displacements are increased by 32.2% and 47.1%, respectively. This study can serve as a solid base for the impact design of FRP bar reinforced seawater sea-sand and concrete beams.

This paper presents research focused on the development of a test method that can be used to gauge the susceptibility of a post- tensioning (PT) grout to form soft grout. Depending on the grout formulation, soft grout may have a lower pH, retain excessive moisture, and be corrosive to the tendon. While relatively rare, it has been documented in bridge construction in the United States and abroad, and in some cases has prompted the replacement of PT tendons. One of the causes of soft grout is thought to be the use of low- reactivity fillers such as ground limestone. When tendons deviate significantly, these fillers can segregate and then accumulate into a mass of material that does not harden. The modified inclined tube test (MITT) was developed based on the Euronorm inclined tube test. None of the commercially available PT grouts produced soft grout when they were mixed and injected in accordance with manufacturer’s recommendations and tested well before their expiration date. Additional mixture water or residual water in the tube, however, produced soft grout consistently in one of the PT grouts.

This study focuses on enhancing the durability of two-component grouting materials by incorporating ground granulated blast furnace slag (GGBFS) and replacing cement with industrial waste to reduce environmental pollution. A ternary cementitious system was developed using 30% GGBFS and 10% carbide slag (CS) as partial cement replacements. The research investigates the effects of different water-bentonite ratios, water-binder ratios, and AB component volume ratios on the physical and mechanical properties of the grout, including density, fluidity, bleeding rate, setting time, and strength performance. The microstructural evolution and hydration products were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and thermogravimetric analysis (TGA). The findings provide insights for optimizing the mix design of grouting materials in shield tunneling applications, with a focus on improving performance and sustainability.