The Effects of Recycled Carbon Fibers on the Mechanical Properties of High-Strength Concrete and Its Resilience to Impact

The presented work investigated the mechanical properties and impact resistance (with a modified ACI test setup) of high-strength concrete by reinforcing it with two different aspect ratios, i.e., 150 for 15 mm fiber length and 250 for 25 mm fiber length of carbon fibers with varying dosages of 0.2, 0.4, 0.6, 0.8, and 1% volume fraction of fibers. Various tests, including flexure tests, compression tests, impact resistance tests, and ultrasonic pulse velocity tests, were conducted on test samples after 28 days of curing in water. Energy-dispersive X-ray spectroscopy along with powdered X-ray diffraction analysis was conducted on samples to find out various chemical compositions of elements present and mineralogical properties, respectively. The surface morphology of concrete samples was determined with the help of scanning electron microscope (SEM) equipment. The mechanical characteristics and impact resistance were connected with an analytical analysis technique. The carbon fiber with the largest aspect ratio of length equivalent to 25 mm showed good growth in the rate of flexural, compressive strength, and impact resistance. SEM images revealed that the primary cause of failure in recycled carbon fibers was the debonding of fibers at fracture surfaces. The increase in carbon fibers' volume fractions or dosages enhances the compressive strength and increases the porosity of concrete samples up to the optimum dosage of recycled carbon fibers. Chemical examination showed that silicon and calcium crystalline were the primary components of the concrete matrix, which suggested that calcium silicate hydrate and calcium hydroxide were the primary hydration products of the cement-based matrix.

Automated summary

This study investigated the mechanical properties and impact resistance of high-strength concrete reinforced with carbon fibers of different aspect ratios and dosages. The results showed that carbon fibers with a length of 25mm exhibited good performance, and increasing the fiber dosage enhanced the strength of the concrete while also increasing its porosity.