Innovations in Sustainable Cementitious Materials, Structural Performance, and Intelligent Monitoring

1. Foreword

The global construction industry is currently undergoing a paradigm shift driven by the urgent need for environmental sustainability and the rapid advancement of digital technologies. As the most widely used man-made material, concrete is at the center of this transformation. Traditional Portland cement production is responsible for a significant portion of global CO₂ emissions [1,2]. Consequently, researchers are exploring innovative binders, supplementary cementitious materials (SCMs), and recycling strategies to reduce the carbon footprint of the industry while maintaining or enhancing structural performance and durability [3]. This collection of ten research articles provides a comprehensive overview of these advancements, ranging from the chemical optimization of self-leveling mortars and hybrid binders to the application of artificial intelligence and low-cost sensors for structural health monitoring.

2. Brief Introduction of the Articles

2.1. A Study on Reactive Ultra-Fine Fly Ash and Sulfoaluminate Cement in Self-Leveling Mortar (Chuang et al.)

Chuang et al. investigate the optimization of self-leveling mortar (SLM) by combining Type I Portland cement, sulfoaluminate cement (SAC), and reactive ultra-fine fly ash (RUFA). SLM requires high fluidity and stability without segregation. The study finds that RUFA, due to its spherical shape and high pozzolanic activity, significantly improves the density of the microstructure and reduces porosity [4]. Although SAC enhances early-age strength, its dosage must be carefully controlled (ideally around 10% volume) to balance drying shrinkage and long-term strength.

2.2. Water Demand of Aggregate as a Dominating Factor for SCC Composition Design (Urban)

Maciej Urban highlights that in the era of superplasticizers, the water demand (or specific surface) of aggregates is an underestimated factor in self-compacting concrete (SCC) design. The author evaluates four analytical models (Bolomey, Stern, Loudon, and Relative Specific Surface) and demonstrates that they all correlate highly linearly with the relative thickness of the cement paste coating the aggregate. This study simplifies the design process, allowing for the determination of the “minimum paste demand line” based on simple aggregate grading data.

2.3. Effect of High Percentages of Coated Recycled Aggregates on RC Beams (Martínez et al.)

This study addresses the limitations of using recycled aggregates (RAs) in structural applications. Martínez et al. tested reinforced concrete beams with 50% and 100% RA replacement, where the RA was coated with a recycled binder paste (RBP) to improve its surface microstructure. Although compressive strength decreased by up to 12.73% for 100% replacement, the beams exhibited cracking patterns and load capacities comparable to or exceeding the theoretical predictions of ACI 318 and Eurocode 2.

2.4. Hybrid Mortars Activated with Alternative Steel-Compatible Salts (Cruz-Hernández et al.)

The research explores hybrid cements—binders with 70–80% industrial by-products (slag) and only 20–30% clinker [5]. Cruz-Hernández et al. focus on the activation of slag-based hybrid mortars using sodium carbonate and sodium nitrate. Carbonate activation proved more effective in reducing porosity, while nitrate activation formed specific phases (nitrate-AFm) that effectively hindered chloride diffusion, suggesting high durability for reinforced structures [6].

2.5. Bulk Electrical Resistivity as an Indicator of Durability (Santos Cortés et al.)

This study evaluates the sustainability and durability of concrete incorporating volcanic ash (VA) and sugarcane bagasse ash (SCBA). Santos Cortés et al. use bulk electrical resistivity (ER) as a non-destructive indicator of the material’s resistance to chloride penetration [7]. The ternary mixture of 5% VA and 15% SCBA showed an ER increase of up to 37% and a CO₂ emission reduction of approximately 16.8%, proving it to be a viable green alternative for coastal construction.

2.6. Impact of Fiber Type on Chloride Ingress in Concrete (Silva et al.)

Silva et al. utilize X-ray macrofluorescence (MacroXRF) to map chloride penetration in concrete reinforced with glass and polypropylene fibers. The findings indicate that while fibers do not increase compressive strength, they effectively mitigate chloride ingress. Polypropylene fibers at 0.25% dosage performed the best, emphasizing that optimal fiber volume is critical for enhancing concrete’s protective capacity in aggressive environments.

2.7. Strength Prediction of Cement-Stabilized Soils (Miturski)

Miturski proposes a novel empirical relationship for predicting the unconfined compressive strength (UCS) of cement-stabilized soils, considering porosity, cement index, and curing time. By developing a nomogram, the author provides a practical tool for highway engineering. The study demonstrates that the cement index is the dominant factor in strength development, while curing time can be mathematically modeled to provide long-term predictions.

2.8. Mesoscale Modeling of the Mechanical Behavior of Metaconcretes (Martínez Raya et al.)

Exploring the frontier of metamaterials, Martínez Raya et al. developed a 2D mesoscale finite element model for “metaconcrete”—concrete with resonant inclusions (steel cores with rubber coatings) designed to attenuate vibrations and shock waves. The study quantifies the strength penalty associated with these inclusions and suggests an optimal resonator content (3–5%) to maintain structural integrity while achieving the desired resonance properties.

2.9. Assessment of Low-Cost Sensors in Early-Age Concrete (Porras et al.)

Monitoring early-age concrete is vital for quality control. Porras et al. validated a low-cost, Arduino-based wireless sensor system to track internal temperature and humidity. The system was successfully tested in both laboratory conditions and on industrial precast New Jersey barriers. The findings confirm that such systems can reliably detect thermal gradients and maturity, providing actionable data for curing management in factory settings.

2.10. Heavy Equipment Detection Using YOLOv10 and Transformers (Eum et al.)

Addressing construction site safety, Eum et al. implemented the YOLOv10 object detection framework integrated with transformer-based backbones (Swin Transformer) to monitor heavy equipment. The model demonstrated high accuracy (AP50 = 89.72%) and real-time processing speeds (35 FPS). This technology allows for continuous safety monitoring, reducing collision risks and improving operational efficiency in complex work environments [8].

3. Discussion

The synthesis of these ten articles reveals a multi-faceted approach to modern civil engineering. First, the focus on sustainable binders—such as RUFA, SAC, slag-based hybrids, and agricultural ashes (SCBA)—underscores a transition toward a circular economy where industrial waste is valorized as a resource. Second, the integration of advanced characterization and modeling techniques, such as MacroXRF imaging for chloride mapping and mesoscale FEA for metaconcretes, allows for a deeper understanding of material behavior beyond traditional macro-scale testing. Third, the adoption of digital technologies, including low-cost IoT sensors and AI-driven object detection, signifies the arrival of “Construction 4.0,” [9] where data-driven decisions enhance safety and quality control.

In conclusion, the research highlights that while sustainable materials often involve trade-offs in mechanical strength (e.g., strength reductions in recycled aggregate concrete or fiber-reinforced mixes), these can be mitigated through innovative coating techniques, optimized mix designs, and precise chemical activation. Furthermore, the ability to predict performance through electrical resistivity and maturity models provides the necessary reliability for industrial adoption.

4. Future Development Directions

Based on the synthesized findings, the following directions are recommended for future research.

4.1. Digital Twins and Real-Time Feedback

Integrating low-cost sensor data with AI models to create “Digital Twins” [10] of concrete elements, allowing for autonomous curing adjustments (e.g., automated misting systems) in precast plants.

4.2. Advanced Surface Engineering

Further refining the coating of recycled aggregates and fibers with nanomaterials to eliminate the strength penalty and enhance the interfacial transition zone (ITZ) [11].

4.3. Long-Term Durability in Extreme Climates

Extending the study of hybrid binders and pozzolanic concretes to long-term exposure in highly corrosive (C-5) or arctic environments to validate service life models.

4.4. Multimodal AI Safety Systems [12]

Combining equipment detection with worker posture analysis and site-wide IoT networks to create a holistic, preventative safety ecosystem.