Optimizing quaternary chemical additives and steel fiber dispersion in CSA cement based HPC for rapid repair engineering

With the rising demand for efficient infrastructure repair, rapid-hardening calcium sulphoaluminate (CSA) cement has gained attention for its fast setting and high early strength, making it ideal for high-performance concrete (HPC) in urgent scenarios. This study developed a CSA-based HPC mix tailored for rapid repair, optimizing dosages of retarder, accelerator, water-reducing agent, and defoamer to balance workability and strength. The addition of 3.5 % steel fibers enhanced 28-day compressive strength and flexural toughness by 66.2 % and 87.73 %, respectively, due to denser hydration products. The effects of steel fibers on mechanical and electrical performance were analyzed, with scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) revealing the influence of microstructure and curing age. Electrical resistivity increased over time but declined quadratically with rising fiber content, showing a power-law relationship with mechanical strength. A slump flow of 225 mm was identified as optimal for uniform fiber dispersion. Overall, this work offers a scientifically grounded approach to designing CSA-based HPC with improved performance, providing a promising solution for fast, durable, and efficient concrete repair in demanding engineering environments. • The orthogonal design methodology is implemented to ascertain four optimal admixture proportions of HPC. • Electrical resistance measurements are employed to dynamically monitor HPC’s mechanical performance. • AC impedance spectroscopy is utilized to assess the dispersion uniformity of steel fibers within HPC.