Mechanical Properties and Microstructure of Cellulose Fiber- and Synthetic Fiber-Reinforced High-Strength Concrete

This study aimed to investigate the effects of cellulose fiber (CF) as a natural waste, glass fiber (GF), and polypropylene fiber (PPF) on the mechanical properties and microstructure of high-strength concrete (HSC). The analysis of the results focused on two main parameters: fiber type and fiber proportion. The study revealed that the proportion of the greatest improvement in compressive strength was 0.5% for GF, CF, and PPF, resulting in increases of 14.46%, 4.62%, and 3.43%, respectively. In terms of the splitting tensile strength, the proportion resulting in the greatest improvement was 1% for GF, while 0.5% for CF and PPF led to increases of 26.92%, 15.38%, and 11.54%, respectively. The proportion with the greatest improvement in flexural strength was 1% for GF and CF, showing increases of 29.41% and 9.8%, respectively. Additionally, a proportion of 0.5% PPF resulted in an 11.76% increase in flexural strength. For the density proportions of GF, CF, and PPF at 1%, the density was greater than 0.5%, leading to an inverse relationship with water absorption as density increased and water absorption decreased. SEM examination of the microstructure clearly revealed strong bonding between the GF and the cement matrix, while the CF displayed bonding and hydration products on its surface. PPF was observed to be cemented within the matrix, with microcracks identified in certain areas. These findings suggest that when utilized in appropriate proportions, all three types of fibers can serve as effective reinforcing materials, enhancing and refining the mechanical properties of HSC.