International Concrete Abstracts Portal

Due to global warming, the temperature of earth surface increased by 0.95 to 1.20℃ in the past 4 decades. The increase in temperature has significant effects on the concrete industry, causing alterations in concrete curing conditions and degradation in strength and durability properties. The understanding of changes in concrete properties due to variations in curing conditions from climate change is an imminent task that has to be resolved. Among the durability properties of concrete, freeze-thaw (FT) resistance is most directly affected by climate change. However, in all of the studies conducted on the FT behavior of concrete, the dramatic changes in environmental conditions due to climate change were not considered. Therefore, the focus of this study is to understand the FT performance of concrete from extreme temperature and relative humidity (RH) changes in curing conditions. To find the relationship between the curing condition change and FT resistance levels as a function of time, a 3-D satisfaction surface graph was developed using the Bayesian probabilistic method. Then, an example of drawing the 3-D satisfaction surface diagrams for FT resistance based on the weather conditions in New York City between 2001 and 2100 was shown. Furthermore, considering the reduction rate of the average annual FT cycle due to climate change, this study confirmed that FT resistance performance increased. This approach contributes to a performance-based evaluation (PBE) strategy for concrete exposed to FT cycles under various environmental conditions. The study details and results are discussed in the paper.

This study employs advanced nonlinear finite element (FE) modeling to investigate interface shear transfer (IST) behavior in reinforced concrete connections, a crucial factor for bridge durability and safety. The research examines shear-transfer mechanisms at the interface between precast girders and cast-in-place deck segments through three experimental methods: beam, pushoff, and Iosipescu four-point bending tests. FE simulations evaluated stress distributions, IST capacity, and failure mechanisms. Validation against experimental data shows that the Iosipescu test provides the most accurate representation of IST behavior, exhibiting a stress distribution error margin of only 1%, closely aligned with observed failure patterns. In contrast, the pushoff test showed a 30% deviation from empirical data, indicating reduced accuracy in predicting real-world IST behavior. These findings highlight the importance of incorporating the Iosipescu test into IST evaluation protocols, as its greater precision enhances design methodologies for concrete bridges, reduces structural failure risks, and informs future updates to IST-related codes.

The durability of manufactured sand concrete is substantially influenced by variations in parent rock lithology, fineness modulus, and stone powder content of the manufactured sand. This study develops a predictive model for the relative dynamic elastic modulus of manufactured sand concrete using six machine learning algorithms. The results demonstrate that the CPO (crested porcupine optimizer)-optimized XGBoost model exhibits superior prediction accuracy and stability. The algorithm-based optimization reveals that manufactured sand produced from limestone, iron ore tailings, and quartzite demonstrates improved frost resistance in concrete. The optimal fineness modulus range was found to be 2.6 to 2.86; stone powder content should be maintained between 3 and 12% for optimal performance. The study further proposes a mixture ratio optimization scheme that takes into account frost resistance, material cost, and carbon emissions, so that the cost and carbon emissions of single concrete are reduced, and the frost resistance is further improved.

Advances in concrete material science have led to the development of a new class of cementitious materials, namely ultra-high-performance concrete (UHPC), which offers superior mechanical and durability properties. The control and characterization of the fresh properties of UHPC are crucial for successful mixture design. Among the methods for evaluating these properties, the mini-cone test has gained prominence due to its practicality. It requires smaller sample volumes than the standard slump cone test, making it especially suited for laboratory assessments of UHPC mixtures. In contrast, the slump flow test is the simplest and most widely used test for both laboratory and field testing of concrete. This study aims to establish a correlation between mini-cone flow and standard slump flow test results. A linear relationship is identified, which forms the basis for proposing consistency classes for UHPC using mini-cone flow values. These proposed classes align with the established consistency classifications for self-compacting concrete.

As recycled concrete reaches the end of its service life, a new generation of coarse recycled aggregate (CRA) is created. Although the variables influencing the physical properties of CRA are well understood, the performance of multi-recycled coarse aggregate (MRCA) remains insufficiently explored, being essential to study how the modified properties could affect the performance of recycled concrete. This research involved five recycling cycles to evaluate the properties of MRCA and its impact on the mechanical and durability performance of concrete made with 75% MRCA. The findings indicate that water absorption, porosity, and abrasion of MRCA increase with each recycling cycle. Although the mechanical behaviour of the concretes appears to be unaffected by the number of recycling cycles, the elastic modulus is negatively impacted when MRCA is used. Furthermore, while some permeability properties are significantly influenced by each recycling cycle, both water penetration depth and resistance to sulfate attack remain largely unchanged.