Microstructural changes and mechanical performance of cement composites reinforced with recycled carbon fibers

In recent years, efforts have been made to utilize recycled carbon fibers (RCFs) into the cement composites. However, limited information is available on the interaction of these recycled fibers with the host cement matrix. Therefore, this study aims to provide a better understanding of the influence of milled recycled carbon fibers (RCFs) on cement composites. For this purpose, six different fiber volume fractions ranging from 0.25% to 1.5%, at an increasing rate to 0.25%, were selected to develop fiber-reinforced cement composites, and a comprehensive research study was conducted to investigate the effect of RCFs on strength improvement, microstructure, crystalline phase change, and hydration products of cement composites over time. The X-ray diffraction analysis, FTIR, and thermogravimetric analysis revealed that RCFs promote the growth of hydration products by providing inert nucleation sites without any additional chemical reaction. The degree of hydration and chemically bound water was increased by 6.64% and 1.59%, respectively, when 1.5% by volume of RCFs were added to the cement composites. The reinforcing effect was most obvious with the addition of 1% by volume of RCFs, by which the flexural and compressive strengths were increased by 82% and 47%, respectively. This study revealed that RCFs have a great potential to be utilized as reinforcement into the cement composites.