Mechanical Behaviors of Microwave-Assisted Pyrolysis Recycled Carbon Fiber-Reinforced Concrete with Early-Strength Cement

Abstract

This study aimed to investigate the mechanical performance of early-strength carbon fiber-reinforced concrete (ECFRC) by incorporating original carbon fiber (OCF), recycled carbon fiber (RCF), and sizing-removed carbon fiber (SCF). Compressive, flexural, and splitting tensile strength were tested under three fiber-to-cement weight ratios (5‰, 10‰, and 15‰). The RCF was produced from waste bicycle parts made of carbon fiber-reinforced polymer (CFRP) through microwave-assisted pyrolysis (MAP). The sizing-removed fiber was obtained through a heat-treatment method applied to the OCF. The results of scanning electron microscopy (SEM) analysis with energy dispersive X-ray spectrometry (EDS) indicated the successful removal of sizing and impurities from the surface of the RCF and SCF. The mechanical test results showed that ECFRC with a 10‰ fiber-to-cement weight ratio of carbon fiber had the greatest improvement in its mechanical strengths. Moreover, the ECFRC with 10‰ RCF exhibited higher compressive, flexural, and splitting tensile strength than that of benchmark specimen by 14.2%, 56.5%, and 22.5%, respectively. The ECFRC specimens with a 10‰ fiber-to-cement weight ratio were used to analyze their impact resistance under various impact energies in the impact test. At 50 joules of impact energy, the impact number of the ECFRC with SCF was over 23 times that of the benchmark specimen (early-strength concrete without fiber) and was also greater than that of ECFRC with OCF and RCF.

A Critical Review on the Application of Recycled Carbon Fiber to Concrete and Cement Composites

“…Patrinou et al [45] concluded that the compressive strength of cement composites increased with an increase in RCF dosage. Li et al [54] demonstrated that concrete composite with 10% of RCF dosage exhibited better compressive strength compared to concrete composites with 5% and 15% of RCF dosages. Similarly, Mastali et al [53] have investigated the influence of RCF dosage on cement composites by adding 0.5%, 1%, 1.5%, and 2% of RCF volume to a cement composite.…”

“…Their study indicated that a further increase in the RCF dosage up to 2.5% regressed flexural strength because of the agglomeration of RCF [45]. Li et al [54] have investigated the flexural strength of early strength concrete by adding a 5%, 10%, and 15% dosage of RCF. Their investigation concluded that a 10% addition of RCF improved the flexural strength of cement composites.…”

“…The use of RCF also improves the tensile strength of cement composites. For example, Li et al [54] have investigated the splitting tensile strength of early strength concrete by adding a 5%, 10%, and 15% dosage of RCF and concluded that, comparatively, a 10% addition of RCF showed a significant improvement in the splitting tensile strength of cement composites. Wang et al [50] have shown that incorporating RCF into cement composites improved tensile strength by 65.3% compared to that of cement-only samples.…”

“…Multiple studies have been conducted over the years on the workability of cement composites with added RCFs. For example, Li et al [54] have shown that the slump values of fresh RCF-added concrete composites is at 150 mm, 80 mm, and 35 mm with additions of 5%, 10%, and 15% RCF, respectively. Faneca et al [34] have investigated the workability of four different dosages of cement composites with added RCFs.…”

Effect of the Sizing Removal Methods of Fiber Surface on the Mechanical Performance of Basalt Fiber-Reinforced Concrete

“…The presence of sizing on the surfaces of fibers can affect the mechanical behavior of fiber-reinforced composites. Cement matrix composite specimens with sizing-removed carbon fibers can attain higher compressive strengths compared to untreated carbon fiber cement matrix composite specimens [28][29][30]. The sizing-removed fibers can be easily dispersed in the cementitious composite, and the bonding between the fibers and the cement can be notably improved.…”