International Concrete Abstracts Portal

The heterogeneous pore structure and weak interfacial transition zones associated with reclaimed asphalt pavement (RAP) aggregates adversely affect the durability of cement concrete. This paper quantitatively evaluates the influence of aggregate packing on pore network characteristics and transport properties of RAP concrete. Concrete mixtures were proportioned using a conventional particle size gradation (PSG) method and a particle packing–based method (PPM). X-ray computed tomography was used to quantify pore structure and connectivity, while sorptivity, open porosity, ultrasonic pulse velocity, and electrical resistivity were measured to assess transport behavior. Compared to PSG mixtures, RAP concrete mixtures designed with the PPM approach showed a more refined pore network, shorter pore throats, and higher tortuosity due to better aggregate packing and reduced meso-scale pore connectivity. These microstructural changes resulted in significant reductions in sorptivity and open porosity, along with improved ultrasonic pulse velocity and electrical resistivity. The results demonstrate that packing-optimized mixture proportioning effectively mitigates transport-related durability concerns in RAP concrete.

The marine environment accelerates the deterioration of concrete’s mechanical properties, necessitating accurate prediction of compressive strength for service life and durability design. Using a marine concrete database, this study develops a Support Vector Machine (SVM) model to examine the impacts of data quality, dataset size, and hyperparameter optimization. Gray relational analysis identifies initial strength, silica fume content, SO₄²⁻ concentration, and exposure age as key factors. Noise simulations reveal that erroneous data significantly reduce predictive accuracy, underscoring the importance of data reliability. As the dataset expands from 500 to 10,000 samples, R² increases from 0.515 to 0.939, while RMSE and MAE decline markedly, though accuracy gains taper beyond 5,000 samples. Bayesian optimization delivers the best performance with an R² of 0.946 and an average relative error of 5.52%, demonstrating its superiority in enhancing model adaptability and prediction precision for marine concrete durability assessment.

Reinforcement corrosion constitutes a major threat to the durability and safety of concrete infrastructure. While the effect of reinforcement corrosion on the flexural strength and bond of reinforcement in reinforced concrete beams has been studied, more research is needed on the effect of corrosion of stirrups and longitudinal reinforcement on their shear strength. This paper focuses on the shear strength of reinforced concrete beams with a shear span to effective depth ratio  2.5. A review of experimental investigations on the behavior of reinforced concrete beams subjected to varying levels of reinforcement corrosion is summarized. The ACI CODE-318-25 shear design provisions are assessed by comparing experimental results with code-calculated strengths. Modifications to improve the safety of the current ACI CODE-318 approach are proposed to estimate the shear strength of slender reinforced concrete beams with corrosion damage.

While the layer-by-layer approach can accurately predict the moment-curvature (M-Phi) response of ultra-high-performance concrete (UHPC) beams, it is computationally intensive and cumbersome for designers. This study proposes a simplified equivalent rectangular stress-block method, aligning with conventional concrete design practices. The proposed method is validated using a database of 224 UHPC beams, including rectangular, T, and I-shaped sections, both prestressed and non-prestressed. The ratio of experimental to predicted moment capacities ranges from 0.95 to 1.13, with an overall average of 1.10 and a coefficient of variation of 16%, demonstrating good accuracy. Parametric analysis indicates that the maximum reinforcement ratio for singly reinforced UHPC beams ranges from 6 to 8%. To ensure ductile behavior and prevent compression-dominant failure in over-reinforced sections, it is recommended to provide compression-side reinforcement up to 50% of the area of primary tension reinforcement. The proposed approach offers a practical tool for UHPC flexural design suitable for researchers and practicing engineers.

A conceptual design screening workflow for reinforced concrete (RC) columns is presented to conjointly minimize raw-material cost and cradle-to-gate carbon footprint prior to reinforcement detailing. The method proposes modifications to ACI 318-19 sizing procedures to incorporate performance-based cost and environmental metrics before reinforcement detailing, thereby enabling rapid screening of candidate concrete mixtures, reinforcement ratios, and column configurations. The workflow is demonstrated on a 12-story building using 30 concrete formulations, four reinforcement ratios, three cross-sectional shapes, and two steel rebar production routes. Results show that: 1) decreasing reinforcing-steel content and the embodied carbon footprint of materials on a per-unit-volume basis does not necessarily minimize the total carbon footprint of RC columns; 2) steel reinforcement can contribute up to three times more embodied carbon than concrete; and 3) eco-efficiency exhibits a weak correlation with binder content and concrete type.