In the marine environment, sulfate ions and chloride ions are abundant. Therefore, sulfate attack and chloride ion attack are common failure forms of marine concrete. Mg–Al hydrotalcite is a layered bimetallic hydroxide, which can be used as guest molecular adsorbent. In this experiment, we synthesized Mg–Al hydrotalcite, and the crystal state, surface morphology, and composition of this adsorbent were investigated by modern micro-analysis technology. Mg–Al hydrotalcite was added into the prepared target ion solution, to explore the influence of various factors on the adsorption performance of Mg–Al hydrotalcite, and then calcined Mg–Al hydrotalcite was added into cement paste, to study the mechanical properties and durability of the paste samples. The experimental results show that the optimum conditions for adsorption of chloride ions by calcined Mg–Al hydrotalcite are an adsorption time of 4 h, temperature of 35 °C, LDO (calcined Mg-Al hydrotalcite) dosage of 3.5 g/L, and a pH of 8. The adsorption effect of sulfate ion is best when the adsorption time is 6 h, the temperature is 35 °C, the dosage of LDO is 4 g/L, and the pH = 8. The optimal adsorption conditions of calcined Mg–Al hydrotalcite for chloride ion and sulfate ion are not completely the same, and the adsorption of these two ions in mixed solution shows competitive adsorption. Compared with the common paste specimens without Mg–Al hydrotalcite, the mechanical properties and deformation properties of cement specimens can be significantly improved by adding Mg–Al hydrotalcite.

High titanium heavy slag is one kind of solid waste that exists in large amounts in the southwest of China. In this paper, this high titanium heavy slag is used as natural pre-wetted material in concrete because of its porous structure. Three kinds of aggregates are used in this concrete. The first one is natural limestone and river sand. The second one is dry slag fine aggregate and coarse aggregate. The third one is pre-wetted coarse slag aggregate and dry slag fine aggregate. The strength, dry shrinkage, autogenous shrinkage, relative humidity, pore size distribution, stress–strain relationship, micro-hardness and chloride penetration of concrete composed of the above three aggregates are tested in this study. The results show that pre-wetted slag aggregate is a suitable internal curing material. The concrete with pre-wetted slag aggregate shows higher strength, lower shrinkage and smaller porosity. The water absorbed in the slag aggregate can be released effectively to increase the relative humidity, accelerate hydration, improve porosity and increase the interface strength.

As one of the important factors affecting the structural durability of cementitious materials, sulphate erosion not only reduces the service life of the material but also poses a threat to the structural safety of the project. At present, scholars around the world have conducted extensive research on topics related to external sulphate attacks and have achieved fruitful results. However, the process and mechanism of attack degradation of the gelling material are not clear. In this paper, gypsum sand was introduced into the mortar. The effects of gypsum content, gypsum particle size and curing temperature on physical properties such as expansion and strength of specimens were investigated. X-ray diffraction (XRD), thermogravimetry (TG), differential scanning calorimetry (DSC), Scanning Electron Microscopy (SEM) and energy dispersive spectrometry (EDS) were used to analyse specimens’ phase composition and microstructure evolution at different attack ages. Finally, cementitious materials’ degradation process and mechanism under internal sulphate attack (ISA) were analysed. Through the above research, the following main conclusions are drawn: (1) The swelling rate of cement mortar specimens all increased with the increase of gypsum dosing; (2) The expansion of cement pastes and mortars does not increase with the increase in curing temperature; (3) The gypsum particle sizes are smaller, the expansion of mortar specimens is larger, and the loss of compressive and bending strength of mortar specimens is large; and (4) The main reaction product of ISA is Ettringite (AFt). The gypsum formed during the ISA process does not cause expansion, while AFt is the main reason for the destruction of the cementitious material.

Microencapsulated phase-change materials (MPCMs) with excellent thermal properties for low-temperature cold storage were developed in this study. Using 1-decanol as the core and methyl methacrylate as the shell precursor, the effects of emulsifier type and ultrasonic emulsification conditions were investigated. Styrene-maleic anhydride copolymer served effectively as a protective colloid emulsifier, producing MPCMs with high enthalpy and a well-defined, uniform microstructure. Under optimal conditions of 5 wt% emulsifier content relative to the oil phase, an ultrasonic power of 375 W, and an emulsification time of 12 min, the MPCMs exhibited a phase-change enthalpy of 126.7 kJ/kg. To further improve the thermal properties, a binary eutectic mixture was prepared by combining 1-decanol and 1-tetradecane at an optimal molar ratio (51.1:48.9). This binary-core MPCM showed a higher storage enthalpy (144.3 kJ/kg), with an increase of 13.9% compared to the single-core material (1-decanol). It also exhibited improved microstructural uniformity due to the stabilizing role of 1-tetradecane. These optimized MPCMs demonstrate phase-transition temperatures particularly suitable for low-temperature thermal storage, providing a practical and innovative technical solution for cold-chain logistics and vaccine refrigeration applications.

Lithium mica slag is a byproduct acquired via the sulfate method of lithium extraction, and it contains a certain quantity of soluble sulfates. The improper storage of lithium mica slag not only takes up a large amount of land resources, but also poses a threat in terms of environmental pollution. Therefore, this study aimed to investigate the mechanism by which SO₄²⁻ dissolves in lithium mica slag, along with the impacts of internal sulfate attacks on mortar specimens with 10%, 20%, and 30% lithium mica slag contents. Testing was carried out in terms of the expansion, mass change, flexural and compressive strengths, porosity, composition, and contents of the products. It was determined that a significant quantity of SO₄²⁻ was generated in mortar specimens with lithium mica slag. The mortar specimens mixed with lithium mica slag produced more ettringite (AFt: 3CaO·Al₂O₃·3CaSO₄·32H₂O), which is the product of internal sulfate attacks. This demonstrates that there was an internal sulfate reaction in the mortar specimens mixed with lithium mica slag. The internal sulfate reaction in mortar samples with lithium mica slag was finished in the later stages. It is noteworthy that the reaction did not lead to any cracking or damage; instead, it later allowed for a retention of strength that was equivalent to the strength of mortar specimens without lithium mica slag. In addition, the partial replacement of cement with lithium mica slag not only reduced the environmental pollution caused by soluble sulfates in lithium mica slag, but also reduced the use of cement and, thus, lowered costs.