Stimuli-responsive polymers (SRPs) provide a promising path towards self-repair of cracks in cementitious materials. This review critically synthesizes SRP-based self-healing in Ordinary Portland Cement (OPC) and alkali-activated/geopolymer systems, based on polymers with moisture, pH, and thermo-responsive properties, including superabsorbent polymers (SAPs), hydrogels, shape memory polymers, and microcapsules. Literature that was published from 2000 to 2025 was screened from the major databases of information. More than one hundred and four relevant studies were chosen for comparative assessment. Quantitative performance indicators such as crack-closure efficiency, mechanical recovery, permeability reduction, and swelling behavior are used to investigate the reported healing performance and to understand the importance of differences in pore-solution chemistry of OPC and geopolymers on polymer activation and durability. The synthesis shows that the current evidence is mostly OPC-centric, while geopolymer applications are still limited in number and have not long-term tested for durability, standardized testing methods are unavailable, and the field-scale validation of these materials is lacking. Key research priorities are identified to facilitate durable polymer design and support more rapid translation of SRP-enabled self-healing systems to sustainable cementitious infrastructure.

Detailed analysis of a natural artinite sample by XRD, TGA, FTIR, Raman and solid state ¹³C CP MAS NMR confirmed a high purity of the sample as well as a crystal structure containing a single carbonate site. The solubility of artinite was experimentally investigated under varying saturation conditions. Undersaturation experiments at 7 to 25 °C, up to 1 year, showed that artinite remained stable in water, and that its solubility was higher than previously estimated in literature. In oversaturation experiments, initially dypingite formed at 7 to 20 °C, which slowly transformed into artinite and hydromagnesite. At 25 °C, no dypingite formation was observed, while initially formed artinite transformed to hydromagnesite within a year. Solubility products for artinite, dypingite, and hydromagnesite at 7, 15, 20 and 25 °C were derived from experimental and literature data. The thermodynamic data allowed calculating the impact of CO₂ pressure and temperature on the stability of magnesium carbonate and hydroxide phases and confirmed that hydromagnesite is more stable than dypingite, artinite, and nesquehonite under near-ambient conditions. Increased CO₂ partial pressure stabilizes nesquehonite while artinite becomes less favored. The revised artinite solubility product indicates that artinite is thermodynamically less stable than hydromagnesite, consistent with observations in MgO-hydromagnesite cements.

Existing mix design methods for underwater anti-washout self-compacting concrete lack reliability due to unclear underwater flow behaviors. This study investigates the workability evolution of this concrete in shallow-water environments. The effects of water-to-binder ratio, superplasticizer, and underwater protective agent dosage on flowability and segregation were examined through systematic experiments. Results indicate that underwater slump flow is significantly lower and flow time markedly longer than in air, while increasing the protective agent dosage improves anti-dispersion stability. Water depth variations within the shallow range showed negligible influence. To interpret these mechanisms, the traditional rheological threshold theory was modified by introducing a mortar film retention coefficient to account for dispersion inhibition and an effective density difference to incorporate buoyancy effects. Based on these improvements, a rheological threshold model and an enhanced mix design method were established. Experimental validation confirms that the proposed model accurately predicts qualified mix proportion regions, demonstrating improved design precision within the tested shallow-water environmental parameters compared to traditional methods. This study provides a systematic methodology for the rational mix design and quality control of underwater concrete.

To ensure the stress characteristics and durability of high arch dams during the construction and operation process in severe cold regions, this study proposes an integrated multifunctional prefabricated insulated formwork (MPIF). The MPIF not only works with cast-in-place arch dams to share stress but also provides life-cycle thermal insulation. Three full-scale specimens were tested under monotonic and cyclic loading to investigate the out-of-plane mechanical behavior of MPIF. Results indicate that under vertical loading, cracks primarily occur at the mid-span of the bottom beam, the beam-column interfaces and the center of the grid slab. At a load of 1000 kN, the out-of-plane deformation remains within the elastic range. Structural deformation varies slightly under different loading conditions. Under cyclic loading, out-of-plane deformation is considerably larger than under monotonic loading, and the bearing capacity decreases markedly. Numerical analyses were performed to evaluate the influence of boundary conditions, slab thickness, loading sequence and bonding strength between new and old concrete on the stress characteristics of the integrated formwork. These findings provide a foundation for the practical application of MPIF in high arch dams in severe cold regions.

Cracks in tunnel linings induce bearing capacity degradation, making the rapid prediction of the damage ratio critical for structural safety assessment. However, quantifying the intrinsic mechanical performance solely from apparent surface cracks remains a challenge. To bridge this gap, this study proposes a physics-informed deep learning framework that maps visual crack features directly to the bearing capacity damage ratio. First, a high-fidelity numerical simulation system is established using the Pseudo-Crack Method implemented on the multi-scale thermodynamic platform. This approach avoids the mesh dependency of traditional fracture mechanics and is rigorously validated against existing physical model tests of lining structures in terms of crack morphology and load-displacement responses. Subsequently, a standardized synthetic dataset is constructed by distilling topological features from in-service hydraulic tunnels and applying a color-coded width visualization strategy. By conducting comparative training across eight state-of-the-art deep learning architectures, the ConvNeXtV1 model is identified as the optimal regressor, achieving a coefficient of determination of 0.89 on the test set. The proposed method effectively acts as a real-time "digital surrogate" for time-consuming non-linear finite element analysis, providing a mechanism-based, efficient solution for structural health monitoring of tunnel infrastructure.

Concrete infrastructure in high-altitude regions suffers from accelerated degradation under low-pressure and high-frequency freeze-thaw cycles, which conventional air-entraining agents often fail to mitigate. This study presents a sustainable multi-scale modification strategy for enhancing the freeze-thaw resistance of concrete made with recycled tunnel muck, tailored for the unique durability demands of high-altitude, cold-region infrastructure. By integrating nano silica and vitrified beads, the approach achieves a synergistic material enhancement: nano silica chemically densifies the matrix and refines the interfacial transition zone, while vitrified beads act as solid air-entraining agents that physically dissipate internal stresses and provide stable microstructural insulation. Mechanically, the modified tunnel muck concrete exhibits significantly reduced strength and mass loss along with improved dimensional stability under low-pressure, high-frequency freeze-thaw cycles where conventional air-entraining agents lose effectiveness. Microstructural evolution reveals that, unlike air-entraining agents-based systems prone to void collapse and hydration discontinuity under such extreme conditions, the synergistic action of nano silica and vitrified beads mitigates damage through pore refinement, internal stress buffering, and interfacial densification. Collectively, these findings demonstrate a robust and scalable material strategy for climate-resilient, resource-circular infrastructure in cold alpine regions.