To reduce the impact of safety risks on assembled buildings, this paper explores the factors affecting the safety risks of constructed buildings from the perspective of linkage between the design and construction phases. The method identifies 10 first-level risk indicators and 25 s-level safety risk indicators in five dimensions of prefabricated components, personnel, management, environment, and technology in both the design and construction phases, utilizing literature induction, expert interviews, questionnaire surveys, and Porter’s diamond model. The structural equation model was used to quantify the weights of the 25 s-level safety risk indicators to highlight the safety risk analysis of the assembled building and avoid risk. The results of the study show that it is important to analyze the safety risk linkage between the design phase and construction phase of the assembled building; from the perspective of the design-construction phase linkage, controlling the safety risk in the design phase can effectively reduce the safety risk in the construction phase.

In the context of intelligent construction and building industrialization, assembly buildings face many challenges in quality management due to their special design and construction characteristics. Therefore, a comprehensive method for evaluating the quality risk of the whole process of assembly building is proposed. This method is based on game-theoretic combinatorial empowerment and three-dimensional cloud modeling. By identifying the key risk factors, analyzing and classifying the quality risks that may exist in the whole process of the assembly building project, using the game theory combination assignment method to determine its comprehensive weight, establishing the game-theoretic-combinatorial-assignment three-dimensional cloud model, calculating and comparing the distance between the evaluation cloud and the standard cloud, and determining the risk level of the indexes, thereby realizing the comprehensive assessment of the quality risk. Example validation shows that the method yields a risk level of II for the whole project, which is more consistent with the actual situation, and by comparing with the two-dimensional cloud model, it further verifies the effectiveness and advantages of the three-dimensional cloud model in identifying the high hidden risks, and provides a new idea and method for the quality management of the whole process of the assembled building.

In order to study the changes in the mechanical properties of road subgrade in cold areas after the freezing and thawing of highways in cold areas, indoor mechanical tests were carried out to investigate the effects of the number of freeze–thaw cycles, freezing temperature, water content, and circumferential pressure on the mechanical properties of road subgrade soil in cold areas after thawing. The mechanical properties of road subgrade soil in cold areas after thawing were measured under different conditions. The test results show that, within the study range: (1) After 7 freeze–thaw cycles, the destructive stress of the subgrade soil decreased from 321.7 kPa to 289.9 kPa, a decrease of 9.9%, and the elastic modulus decayed by 19.9%. (2) When the freezing temperature was reduced from −5 °C to −15 °C, the destructive stress of the subgrade soil decreased from 303.9 kPa to 290.1 kPa, a decrease of 13.8 kPa, approximately 4.5%, and the decrease in modulus of elasticity was about 1.6%. (3) The water content increased from 6% to 12%, and the destructive stress decreased from 405.43 kPa to 288.4 kPa, a decrease of 29.1%, and the modulus of elasticity decreased approximately linearly, with an attenuation of 50.4%. (4) The peripheral pressure increased from 50 kPa to 150 kPa, and the destructive stress increased from 194.7 kPa to 367.7 kPa, a growth of 88.8%, and its modulus of elasticity increased with the increase in peripheral pressure, an increase of 154.1%. The results of this research can provide a reference for highway and engineering construction in the western silt–soil distribution area.

To enhance the mechanical properties and low-carbon characteristics of industrial solid waste concrete, this paper proposes a synergistic modification strategy using nano-SiO₂ and sodium silicate. The nano-SiO₂ sol and sodium silicate activator were prepared using magnetic heating and stirring technology, and a quadratic regression model (R² = 0.9575, p < 0.0001) for compressive strength with three factors and three levels was established using the response surface method (RSM-CCD). The modification mechanism was verified through optimization of the mix ratio using a desirability function, along with microscopic characterization via SEM and XRD. The results indicate the following: (1) the content of nano-SiO₂ (2.4%) contributed the most to the compressive strength of the concrete, and its interaction with sodium silicate (2.1%) significantly promoted the formation of C-S-H gel; (2) the optimized fly ash substitution rate (21.7%) can achieve a 28-day compressive strength of 34.8 MPa, with the model prediction error controlled within 5%; (3) microscopic analysis showed that the synergistic effect of multiple components lowered the volume porosity of the cementitious phase, forming a densified network structure. The multi-factor synergistic optimization approach for nano-SiO₂-modified alkali-activated concrete (NS-AAC) proposed in this study offers a reference for multi-objective mix design optimization of industrial waste-based concrete.

The complexity of construction in prefabricated buildings makes it vulnerable to uncertainty in project timelines, and traditional project timeline management is insufficient to control project timelines for prefabricated buildings. Therefore, research on project timeline management for prefabricated buildings is needed in order to optimize project timelines and improve project execution rates. This study proposed an improved method of setting prefabricated building buffer zones through the use of improved grey critical chain technology. Five major factors affecting project timelines in actual prefabricated construction projects were selected: personnel experience, degree of prefabrication, technical complexity, reasonableness of construction plans, and degree of construction space availability. The OPA technique was introduced and combined with the entropy weight method to improve the comprehensive weight coefficient of the grey critical chain calculation of the factors affecting the timeline. Other influencing coefficients were determined, and a new calculation method for the size of prefabricated building buffer zones was proposed. Monte Carlo simulations were conducted in Matlab on actual construction projects to ensure the scientific rationality of the improved method. The results showed that compared with the classical buffer calculation methods (cut-and-paste method, C&PM and square root standard deviation method, RSEM), the project timeline was reduced by 14.3% and 11.7%, respectively, using the improved method. The improved method not only reduces project uncertainties, but also achieves the goal of optimizing project timelines, and it is reasonable and effective. The results of the study provide a direction for the project timeline management of prefabricated building critical chains, and this method can be applied to the planning and management of prefabricated building buffer zones.

To address the poor resistance of recycled aggregate concrete (RAC) to chloride ion penetration and freeze–thaw deterioration in cold coastal regions, this study introduces basalt fibers (BFs) as a reinforcement to improve its durability and structural integrity. Rapid freeze–thaw and electric flux tests, combined with scanning electron microscopy (SEM), were employed to systematically evaluate the effects of fiber volume fraction and length configuration on the frost resistance and chloride impermeability of basalt fiber-reinforced RAC (BFRAC). The experimental results demonstrated that the incorporation of basalt fibers markedly enhanced the coupled durability of RAC, with the mixture containing 0.15% fiber volume and a balanced hybrid of short (12 mm) and long (18 mm) fibers achieving the most favorable performance. This mixture effectively reduced mass loss and strength degradation under repeated freeze–thaw cycles while substantially lowering chloride ion penetration compared with plain RAC. Microstructural observations revealed that the hybrid fiber system formed a multi-scale three-dimensional network, in which short fibers restrained microcrack initiation and long fibers bridged macrocracks, jointly refining the pore structure and improving the interfacial bonding between recycled aggregates and the cement matrix. This synergistic mechanism enhanced matrix compactness and obstructed chloride transport, leading to a more stable and durable composite. The findings not only establish an optimal basalt fiber design for improving RAC durability but also elucidate the fundamental mechanism underlying hybrid fiber synergy. These insights provide valuable theoretical guidance and practical strategies for developing sustainable, high-performance concrete suitable for long-term service in cold-region coastal infrastructures.