Improvement of carbon fibers dispersion in cement‐based materials by mixed‐grinding

Abstract The uniform dispersion of carbon fibers (CFs) is essential for improving the performance of carbon fiber‐reinforced cement‐based materials (CFRC). This study proposes a method for mixing‐grinding and dispersing CFs with cement powder as a pretreatment, aimed at preparing high‐performance mixed‐grinding carbon fiber‐reinforced cement‐based materials (MCFRC). Microscopic techniques were employed to analyze the dispersion behavior of mixed‐grinding carbon fibers (MCFs) within cement powder and slurry matrices. The effects of different mixed‐grinding conditions on the degree of fiber bundle separation and the uniformity of fiber monofilament dispersion were thoroughly examined. Additionally, the impact of fiber content and mixed‐grinding time on the flowability, mechanical strength, and electrical resistivity of MCFRC was investigated. Scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP) analyses were utilized to qualitatively evaluate the dispersion characteristics of CFs within the cement‐based materials. Experimental results indicate that the mixed‐grinding dispersion method effectively breaks down carbon fiber bundles into individual filaments and uniformly disperses them within the cement‐based material. Mixed‐grinding dispersion significantly enhanced the workability, mechanical properties, and electrical performance of MCFRC. When the CFs content was 1.5% and the mixed‐grinding time was 3 min, the individual filaments were uniformly and directionally dispersed in the cement matrix, significantly improving the flowability and flexural strength of MCFRC. Simultaneously, the uniformly dispersed filaments within the matrix formed a stable conductive network, facilitating the flow of electric current and significantly reducing the resistivity of MCFRC. SEM and MIP analysis results reveal that mixed‐grinding dispersion breaks down CFs bundles into individual filaments, which are uniformly and directionally dispersed in the cement matrix, effectively reducing fiber agglomeration, enhancing the bond between fibers and matrix, and decreasing the number of harmful large pores, thereby improving the structural density of MCFRC.