As environmental noise pollution becomes increasingly severe, concrete noise barriers have been widely used in noise control applications due to their excellent durability and cost-effectiveness. However, conventional concrete barriers still have shortcomings in sound absorption and insulation performance, making it difficult to meet the comprehensive demands of lightweight design, functional integration, and environmental sustainability simultaneously. Existing research has improved the noise reduction capability of concrete at the material level by incorporating components such as foaming agents and porous lightweight aggregates into cement-based systems. By adjusting material density, porosity, and pore connectivity, the pore structure and acoustic energy dissipation mechanism of the material have been optimized. On this basis, 3D printing provides a new way to achieve complex geometric designs, lightweight manufacturing, and structural personalization for noise-reducing elements. The directional interconnected pore networks and unique interlayer interface characteristics formed during the printing process can effectively extend the sound wave propagation paths and enhance energy dissipation, thus achieving acoustic performance optimization at the structural level. This article systematically summarizes the key factors and their control strategies affecting the noise reduction performance of concrete, focuses on analyzing the mechanisms by which 3D printing processes regulate pore distribution, interlayer interfaces, and surface textures, and summarizes relevant engineering application cases. Existing research indicates that properly designed 3D-printed concrete structure exhibits significant advantages in mid-to-low-frequency sound absorption, while further targeted optimization of acoustic performance can be achieved by coordinated regulation of geometric configurations and surface textures. In addition, 3D-printed noise-reducing concrete holds significant application potential in road noise barriers and architectural acoustics, though it still faces technical challenges such as material printability, interlayer bond strength and long-term service performance. Future research should focus on the utilization of green and low-carbon raw materials, multi-scale structural design, and durability assessment to promote the high-performance development and engineering application of 3D-printed noise-reducing concrete.

Understanding the composition and reactivity of formic acid modified steel slag powder (SS) from micro scale is critical to extending the utilization of steel slag. In this study, four representative sources of SS were selected, which were dry chemically modified by formic acid (FA) with a mass fraction of 4 % on the basis of SS. The backscatter electron microscope, hydration calorimeter, X-ray diffractometer and fourier transform infrared spectrometer were applied to characterize the SS and SS pastes before and after modification. Results show that the 3 d and 7 d compressive strength of the different sources of SS pastes are low, and the 72 h cumulative hydration heat varies between 10~40 J/g due to their different mineral compositions. However, after FC modification, the 3 d compressive strength increases by more than 200 %, and the 72 h cumulative hydration heat rises to above 50 J/g with an increase above 80 %.it is found that the Ca(OH)₂ in SS can react with FA to produce calcium formate, while the calcium silicates in SS are not significantly affected.