Phosphorus slag (PS), an industrial waste slag, has been used in geopolymers because it is rich in silicon and calcium. The poor performance of phosphorus slag-based geopolymer is due to its aluminum deficiency. In this work, low-calcium fly ash, treated by a wet-grinding process, named wet-grinding ultrafine fly ash (WUFA) was used as an Al supplement to replace some of the phosphorus slag, and the wet-grinding, ultrafine fly ash-phosphorus slag (WUFA-PS)-based geopolymer was prepared. The effects of the substitution amount of WUFA and the activator dosage on the hydration properties, mechanical properties, pore structure and SEM of the WUFA-PS geopolymer were discussed in detail. The results indicate that WUFA and more activators contribute to the Al and high alkalinity environment, which positively induces the production of more geopolymer gels, thus releasing more heat and optimizing the pore structure of the matrix. The compressive strength increased by up to 28.1%. The enhanced performance of the WUFA-PS-based geopolymer may also arise from the filling effect and activity improvement of WUFA. This study has proved the feasibility of preparing a geopolymer by blending wet-grinding ultrafine fly ash and phosphorus slag and has provided references for the ratio and performance evaluation of WUFA-PS-based geopolymer concrete.

With the rapid development of prefabricated bridge construction, traditional manual bending and welding techniques for stirrups increasingly reveal limitations in efficiency, quality, and safety. To promote intelligent technologies in smart girder yards, this study establishes and reports an automated logistics system covering the entire workflow of bending–delivering–welding–storage for reinforcement processing, alongside key innovations, including an integrated stirrup bending workstation, an intelligent rebar cage welding station, and laser-adaptive seam-tracking technology. The results demonstrate that the system achieves fully automated and standardized construction of rebar cages, achieving 100% compliance in quality parameters (e.g., rebar spacing) while eliminating quality risks. Implementation in the G107 Chinese National Highway retrofit project reduced the site footprint by 27%, labor input by 40%, and construction duration by 60% compared with conventional prefabrication yards, saving CNY 3.38 million per thousand girders and reducing rebar consumption by 50 metric tons. This research provides a replicable technical pathway for intelligent bridge construction and significantly advances the mechanization and digitalization of rebar processing and welding.

To tackle the shortage of river sand resources and excessive carbon emissions in building materials, environment-friendly concrete can be fabricated by solidifying aeolian sand and natural gravel with a fly ash-based geopolymer. Aeolian sand and natural gravel are accessible building materials, but their engineering applications are largely limited by their poor properties such as high mud content, large specific surface area, and discontinuous particle size distribution. To enhance the application of this environment-friendly concrete, in this paper, 48 sets of specimens with different geopolymer dosages, curing temperatures, and curing times are studied experimentally, and quite well-strengthened geopolymer aeolian sand mortar (GAM), geopolymer aeolian sand concrete (GAC), and an appropriate dosage of the geopolymer are finally obtained. The experimental results and the failure section of the mortar specimen indicate that the fly ash geopolymer can solidify the aeolian sand and ensure the integrity and compactness of the specimen. The 28-day compressive and flexural strength of the geopolymer standard sand mortar (GSM) reached 40.5 MPa and 4.3 MPa, respectively, at a curing temperature of 60 °C when the amount of alkali activator was improved to 100%, and the 28-day compressive and flexural strength of GAM reached 33.7 MPa and 4.2 MPa, respectively, when the amount of geopolymer material was 0.75 times that of aeolian sand. A lower compressive strength of GAC was obtained following the addition of aeolian sand. The experiment results can provide a reference for aeolian sand usage and have a certain social value in environmental protection.

Fully prefabricated bridge construction technology has gradually replaced traditional cast-in-place methods, becoming a core approach for efficient, environmental, and intelligent construction of bridges in cities. However, due to city-embedded restrictions, i.e., large width for more lanes, prefabricated cap beams in municipal bridges often demand segmental prefabrication and multi-point lifting, which hinders the overall construction efficiency. Based on a real project, this paper proposes a vertical rotation construction method for the bridge substructure, achieving integrated vertical rotation and positioning of prefabricated cap beams and piers by designing rotating steel shoes at the bottom of piers. This approach avoids segmental lifting of extraordinarily heavy cap beams while eliminating the need for prestressing and grouting operations high above the ground. Subsequently, detailed finite element models for critical rotational components, such as steel shoe, hinge pin and lug plates, are established to verify the stress distribution under various rotation conditions. The results demonstrate that the proposed layout, consisting of four 60 mm diameters 40Cr steel hinge pins with Q345 steel shoe and lug plates, effectively controls the representative stress within yield under all conditions, leaving the 10° scenario most unfavorable. Compared with the 10° rotation scenarios, increasing the initial rotation angle to 20° reduces the most critical stress inside the steel shoes by up to 39%, while further increasing to 30° only produces an additional 1% stress reduction. The design parameters of auxiliary equipment for the vertical rotation process can provide valuable references for future engineering practices.