Carbon fiber is a very thin and slender material, like a filament, which can be cut continuously. Their excellent mechanical properties, low specific gravity and chemical stability make them widely used, such as in construction, aerospace, automotive and other industries. Metal elements have been replaced by carbon fiber elements. Due to lower cost and higher fatigue resistance, corrosion resistance and corrosion resistance, the demand for carbon fiber has been on the rise all over the world.
The waste generated in the carbon fiber manufacturing process, such as products that are about to expire, are actually still very useful. This article mainly proves a new method of carbon fiber recycling and how carbon fiber can control concrete crack propagation.
Cylindrical concrete specimens were prepared with cement as raw materials, with a mixing amount of 370 kg/m3, a water-cement ratio of 0.5, and a carbon fiber waste mixing amount of 2% cement mass. Although the processability is low in the fresh state, the results show that the mechanical properties are better in the 28-day test, and the compressive strength and tensile strength of the composite material are improved. In order to explain the relationship between the structure and performance of the new composite material, the image of the fiber was analyzed and the fracture surface of the concrete was analyzed by scanning electron microscope (SEM). Carbon fiber directly acts on the cracking mechanism at the moment of concrete rupture, inhibiting the cracking of the concrete and the formation of large cracks. Carbon fiber waste is added to concrete to provide mechanical improvements and reduce maintenance requirements, thereby increasing the durability of the concrete structure and the sustainability of the building.
The materials used in the concrete are mixed, including traditional and carbon fiber waste concrete as ⅱ Portland slag as shown in Table 1;
The characteristic size of the maximum gneiss gravel is 25.0 mm; the fineness modulus of medium natural (washed) sand is 2.42, as shown in Table 2.
The particle size of concrete aggregates is evaluated. Both fine-grained (sand) and coarse-grained (gravel) aggregates meet the requirements of the ABNT NBR 7211:2019 standard.
Figure 1 shows the particle size curve of natural medium sand, and Figure 2 shows the particle size curve of gneiss gravel (No. 1).
The carbon fiber blanket shown in Figure 3 is produced by MC-Bauchemie as a roll-up fabric, showing that the fiber is cut into pieces with a length between 40 and 50 mm.
Shown in Figure 4. According to the supplier’s notice, the tensile strength of carbon fiber is 4.90 MPa, the modulus of elasticity is 230 GPa, and the elongation break is 2.10% (Mc-Bauchemie, 2008). Used for the mixture is not impregnated with any product.
Granularity curve of natural medium sand washing
Gravel size curve of gneiss
Carbon fiber felt
Discontinuous carbon fiber with length between 40-50 mm
New concrete image: (a) conventional reference concrete; (b) concrete with 2% carbon fiber waste
Slump consistency test: (a) conventional reference concrete; (b) concrete containing carbon fiber waste
The research in this paper fills in the new recycling technology in the recycling of carbon fiber. The proposed recycling method is not only low-cost but also capable of recycling a large amount of carbon fiber waste worldwide.
In addition, this new composite material can provide a longer service life for concrete structures to reduce maintenance and improve the durability of building structures around the world.