Cement concrete is sensitive to cracking during service due to its brittleness and early susceptibility to shrinkage and deformation, further leading to the water seepage and leakage of concrete structure. The timely and effective repair of water leakage in cracked concrete has attracted recent attention in engineering. Superabsorbent polymer (SAP) hydrogel is a new type of self-sealing agent developed in recent years, which has the characteristics of rapid water absorption and significant volume expansion, and has a promising application potential in crack healing and sealing in humid environment. This review represented the basic design method of self-sealing cement-based materials based on hydrogel, discussed the working mechanism of SAP hydrogel as self-sealing agent and its effect on the anti-permeability, mechanics and durability recovery of concrete, and summarized the evaluation method of crack healing and sealing efficiency. In addition, the main challenges and future directions of hydrogel based crack self-sealing technology were also proposed.

Y-doped BaZrO₃ proton conductor has been extensively studied due to its outstanding chemical stability. However, the high sintering temperature has limited its practical application. To enhance the sintering activity of BaZrO₃, we co-doped Y-BaZrO₃ with Pr³⁺ and Ni²⁺, and investigated its microscopic morphology and electrochemical properties. The introduction of Ni forms a solid solution with the sample, while Pr³⁺ doping increases the grain size, a critical factor for the densification process. XPS, Raman and EPR results reveal that a small amount of Pr³⁺ doping significantly raises the concentration of oxygen vacancies in the materials. This increase promotes proton incorporation by accelerating the dissociation and adsorption of water, thereby facilitating the proton conduction. However, it's important to note that excessive Pr³⁺ doping leads to a high concentration of oxygen vacancies, which triggers a defect association reaction. Consequently, this results in a slight decrease in conductivity at low temperatures. On the other hand, as the temperature increases, the hydrogen permeability of the membrane increases also rises. Moreover, the hydrogen permeability of BaZr_0.66Y_0.2Pr_0.1Ni_0.04O_3-δ is found to be higher than that of BaZr_0.71Y_0.2Pr_0.05Ni_0.04O_3-δ, with the former reaching 2.60×10^-8 mol·cm^-2·s^-1 at 1 173 K. Notably, these membranes exhibit remarkable in CO₂-containing atmosphere indicating excellent resistance to CO₂.

In the field of backlight liquid crystal display (LCD), narrow-band green-emitting phosphor plays an important role in expanding the color gamut, improving luminous intensity and optimizing color rendering performance. This review represented recent research progress on the narrow-band green emission phosphors. The phosphors classified by different activating ions, i.e., Eu²⁺ and Mn²⁺, were introduced, and the relationships between their structures and luminescence properties were analyzed. In addition, the advantages and disadvantages were described and the future development were also prospected.

In our natural environment, mechanical energy has the advantages of universality, diversity, no pollution and easy collection, and occupies a place in various forms of energy. The use of piezoelectric nanogenerators to collect this mechanical energy can provide a feasible solution for the power supply of intelligent functional electronic devices. A BaTiO₃/PDMS and BaTiO₃/PDMS/C based composite nanogenerator was prepared with lead-free barium titanate (BaTiO₃) nanoparticles, carbon nanotubes, and polydimethylsiloxane (PDMS). The results show that the output signal of BaTiO₃/PDMS based composite nanogenerator firstly increases, and then decreases with increasing BaTiO₃ content. The optimal output signal is obtained at BaTiO₃ content of 12%, and the output current and output voltage are 42 nA and 18 V, respectively. The output signal of BaTiO₃/PDMS based composite nanogenerator is further improved with introducing C nanotubes. The BaTiO₃/PDMS/C based piezoelectric nanogenerator has the optimal output signal when the content of C nanotubes is 2%, and the output current and output voltage are 73 nA and 19 V, respectively. The results indicate that BaTiO₃/PDMS/C based piezoelectric nanogenerator has a great application potential in self-powered microelectronic wearable devices.

Reversible protonic ceramic electrochemical cell (R-PCEC) is an emerging and efficient energy conversion device that can convert chemical energy into electrical energy and electrical energy into chemical energy. The reversible operation of R-PCEC in the dual mode of fuel cell and electrolytic cell is highly flexible and is one of the most promising ways for efficient energy conversion and storage. However, for R-PCEC, the electrolyte conductivity, catalytic activity of the cathode and anode, and durability under actual operating conditions are the main factors restricting its performance. This review introduced the research and development status of each component of R-PCEC in detail, including electrolyte materials, hydrogen electrodes, and air electrodes, as well as mainly focused on the latest progress on material requirements, electrode performance and reaction mechanism of air electrodes for reversible batteries. In addition, the future developments on R-PCEC were also prospected.

Effect of carbonation curing on the early resistance to carbonic acid solution corrosion of cement-based materials was investigated. The compressive strength, and corrosion depth of carbonation cured specimens were tested after immersion in carbonic acid water for varying periods. The microstructure and corrosion mechanisms were analyzed by X-ray diffraction, thermogravimetric analysis, low-field nuclear magnetic resonance, and scanning electron microscopy. The results show that carbonation curing improves the initial compressive strength via forming calcite to fill pores, making the structure more compact and hindering inward diffusion rate of carbonic acid solution. A dense, slower-dissolving calcite layer around C-S-H gel reduces calcium-corrosion, decreasing both the corrosion depth of mortar specimens by 51%-68% after 90-d immersion and losing the strength after carbonic acid water corrosion. The early-stage corrosion was dominated due to C₃S, C₂S, and CH corrosion, accompanied by CaCO₃ decalcification. The middle- and later-stage corrosion involves the decalcification of CaCO₃ and C-S-H gel.

The characteristics of seawater sea sand concrete become a recent research issue, while the alkali-silica reaction (ASR) of seawater sea sand concrete is still unclear. To clarify the influence of supplementary cementitious materials on the alkali-silica reaction characteristics of seawater and sea sand concrete, the cement-metakaolin-fly ash-slag cementitious materials were designed by a simplex centroid design method. The effect of supplementary cementitious materials on the ASR products, pore structure, pore solution pH value, alkali ion content and expansion rate of seawater and sea sand concrete was investigated. The results show that the content of the amorphous product ASR-P1(K_0.52Ca_1.16Si₄O₈(OH)_2.84·1.5H₂O) and the crystalline product Na-shlykovite (NaCaSi₄O₈(OH)₃·2.3H₂O) in seawater and sea sand concrete are inversely proportional to the content of active SiO₂ and Al₂O₃ in supplementary cementitious materials. Among the seawater and sea sand concretes with different cementitious materials, the pH value of paste prepared with 50% cement+25% metakaolin+25% fly ash and the contents of Na⁺, K⁺ and Ca²⁺ are the minimum values. As a result, the content of ASR-P1 and Na-shlykovite, the content of harmful pores and multi-harmful pores are the minimum values, as well as the porosity is the maximum value, thus resulting in the minimum expansion rate of the paste prepared with 25% metakaolin+25% fly ash +50% cement at 14 d and 28 d. This paper can provide a theoretical basis for the design of cementitious material composition of seawater and sea sand concrete, and improve the service life of seawater and sea sand concrete structure in marine engineering.

Sulfate-rich belite sulfoaluminate cement is used in rapid construction of marine engineering, but the strength of the clinker developed is not enough in the later period. The improvement of the strength in the later stage was investigated via boron/phosphorus composite doping. The effect of boron/phosphorus composite doping on the mineral formation, microstructure, and hydration of high sulfur belite aluminate clinker was analyzed by X-ray diffraction combined with Rietveld full spectrum quantitative analysis, scanning electron microscopy, isothermal calorimetry and thermogravimetric analysis. The results show that boron and phosphorus both can exist in the crystal structure of dicalcium silicate, form the crystal defects, and increase the content of α-C₂S and c-C₄A₃$, thus promoting the early hydration and later strength development of the clinker.

A foam insulation material was prepared by a wet foam mixing method with recycled powder and slag as main raw materials. The effects of alkali activator CaCl₂·6H₂O dosage and the preformed foam on the performance of foam insulation materials were investigated via testing the stabilization time of the foam, the condensing characteristics of the slurry, as well as the compressive strength, dry density, porosity and thermal conductivity of the specimens. The pore structure and reaction mechanism were analyzed by image analysis and X-ray diffraction. The results show that the compressive strength of the specimens firstly increases and then decreases with the increase of alkali exciter, and it reaches the maximum value at 5% of alkali activator, but the dosage of alkali activator has little effect on the porosity and dry density. The addition of CaCl₂·6H₂O significantly shortens the setting time of the slurry, thus favoring that the slurry and the prefabricated foam reach a better matching state, effectively refine the pores and improve the compressive strength and thermal inertia of the specimens. Different density grades of foam insulation materials can be prepared at different amounts of foam admixture. The pore size distribution becomes wider and the compressive strength and thermal conductivity decrease with the increase of foam admixture. The activity of both slag and recycled powder can be effectively stimulated, which can play a coordinating and complementary role to achieve the effect of synergistic utilization of solid waste.

Ultra-high performance concrete (UHPC) is a new cement-based composite material with ultra-high strength, high toughness, and excellent durability. Low water-to-binder ratio and large amount of fine particles in UHPC lead to some problems like high viscosity of fresh paste, fiber cluster issue, and difficulty in pumping, etc.. This is not beneficial to the homogeneity of concrete and fiber strengthening and toughening of UHPC, and restricts the in-situ placing and application of UHPC. This review represented the rheological properties of UHPC from aspects of rheological parameters and models. Based on the influence of water-to-binder ratio, chemical admixtures, mineral admixtures, fiber and aggregate characteristics on the rheological properties of UHPC, the techniques in regulating the rheological behavior of UHPC were analyzed. Such techniques include regulating water film thickness, regulating paste film thickness, reducing viscosity of interstitial fluid, adding viscosity modifier, and changing fiber characteristics. In addition, the rheology regulation mechanisms associated with these techniques were also discussed.