Recycled fiber reinforced concrete

Recycled fibers from various sources have been studied as reinforcement in concrete, including tire cords, carpet fibers, feather fibers, steel shavings, wood fibers from paper waste, and high-density polyethylene.  

1 Typical flexural test curves of fiber reinforced. 

The compressive test was condncted on 76 mm (diameter) by 152 mm (height) cylinders according to ASTM C39-86 at an age of 28 days. As seen from Table 14.1, the compressive strengths varied from mix to mix, most likely due to normal variation. However, it appears that the compressive strength for Mix 8 with 1.4 vol% waste fibers was lower due to the fiber addition. In all the tests, good shatter resistance was observed because of the fiber reinforcement, especially in those with relatively high fiber dosage rates (Mixes 5-8). 

It can be observed from the data in Table 14.1 that the index was insensitive 

Wu et studied the use of recycled fibers from used tires and carpet in 

---

This paper summarizes the results of an experimental program to evaluate the effectiveness of using recycled fibers from carpet waste for concrete reinforcement. It also discusses issues that need to be addressed for the application of such FRC in large scale construction projects. It then reports on a building construction project using carpet waste fiber reinforced concrete. The results suggest that using carpet industrial waste fibers in construction would not only improve the reliability and life of the concrete structure, it but also could reduce the landfill spaces needed to dispose the waste material. 

Wang, Y., Zureick, A.H., Cho, B.S., and Scott, D.E. (1994) Properties of fiber reinforced concrete using recycled fibers from carpet industrial waste. Journal of Materials Science, Vol. 29, No. 16, pp. 4191—4199. 

YoujiangW (1993) Fiber reinforced concrete using recycled carpet industrial waste and its potential use in highway construction. Symp Proc on Recovery and effective reuse of discarded materials and by-products for construction of highway facdities, October 1993, Denver, CO... 

Keywords pitch-based high performance-type carbon continuous fiber reinforced plasUc, chemically resolvable resin, environment-conscious materials (ecomaterials) design, deformed rebar, hybrid structure, lighweight precast concrete, recycle, service life,... 

From the viewpoint of the easiness of demolition and recycling, not ordinary steel reinforced concrete (RC) cast-in place completely in a body, but hybrid structural systems composed of steel reinforced precast RC columns and new continuous fiber reinforced plastics (FRP) reinforced lightweight precast concrete (FRPRC) beams connected with steel fasteners are recommended. 

The carpet industrial waste generated each year and that accumulated in landfills represent an abundance of useful resources, as they can provide effective reinforcement for concrete. As to be discussed in the following sections, concrete reinforced with recycled fibers from hard carpet waste is indeed a suitable material for construction. It suggests that using carpet waste in construction could be a very cost-effective way to improve the durability and performance of the concrete structure, and to reduce the needs for landfill spaces. 

The laboratory study described above demonstrated that recycled fibers from carpet industrial waste can provide effective reinforcement for concrete. However, concerns do exist that must be addressed before such FRC can be widely accepted for construction. 

Cost is another concern associated with the use of recycled carpet waste fibers in concrete. Currently a vast amount of carpet waste is disposed of each year and therefore the cost of raw material for the recycled fibers is negligible. The disassemble process to convert the waste into fibers suitable for concrete reinforcement requires only simple, inexpensive shredding operation. Therefore the cost of the recycled fibers will remain very competitive with virgin fibers for FRC. 

Many carpet manufacturers, fiber and chemical suppliers, recycling companies, and academic institutions are actively pursuing various methods to recycle fibrous waste. The approaches include chemical processes to depolymerize nylon and other polymers, recovery of plastic resins from carpet fibers, direct extrusion of mixed carpet waste, composites as wood substitutes, fibers for concrete and soil reinforcement, waste-to-energy conversion, and carpet as feedstock for cement kilns. 

Other tertiary recycling processes that have been developed include a Freeman Chemical Corp. process to convert PET bottles and film to aromatic polyols used for manufacture of urethane and isocyanurates. Glycolized PET, preferably from film, since it is often lower in cost than bottles, can be reacted with unsaturated dibasic acids or anhydrides to form unsaturated polyesters. These can then be used in applications such as glass-fiber-reinforced bath tubs, shower stalls, and boat huUs. United States companies that have been involved include Ashland Chemical, Alpha Corp., Ruco Polymer Corp., and Plexmar. Unsaturated polyesters have also been used in polymer concrete, where the very fast cure times facilitate repair of concrete structures. Basing polymer concrete materials, for repair or precast applications, on recycled PET reportedly leads to 5 to 10 percent cost savings and comparable properties to polymer concrete based on virgin materials. However, they are still approximately 10 times the cost of portland cement concrete. There appears to be little commercial application of these processes at present. 

Use of the products of chemical recycling of PET in the production of new PET resin has already been mentioned. In addition, the products from chemical recycling can be used as a feedstock in manufacturing of unsaturated polyesters, often for glass fiber-reinforced applications such as bath tubs, shower stalls, and boat hulls. Unsaturated polyesters have also found uses in polymer concrete. 

A total of four types of recycled fiber plus two types of virgin fiber were used as the reinforcement in concrete. Three recycled fibers were obtained from disposed tires and one from carpet waste. The tire fibers included two types of tire fabrics composed of polymeric tire cords, tire-rubber strips which were the main component of tires, and tire steel fibers which were the radial steel reinforcement of tires. The fibers from carpet waste contained backing fibers (nsually polypropylene), latex adhesive particles, and a small amount of face fibers. In addition, hooked end steel fibers and FiberMesh polypropylene fibers were also used as virgin fibers for comparison. Recycled fiber volume fractions in each composite were fixed at 2% except that the tire steel fiber and the virgin fibers (steel fiber and FiberMesh) were used at a 1 vol%. 

In a study on concrete reinforcement with carpet waste fibers [78, 79], recycled carpet waste fibers about 12-25 mm in length and fiber volume fractions of 1 and 2% were used. FiberMesh, a virgin polypropylene (PP) fiber (19 mm long), at 0.5 and 1% volume fractions was included for comparison. 

Utilization of recycled carpet waste fibers for reinforcement of concrete and soil... 

Wang Y. (1999), Utilization of Recycled Carpet Waste Fibers for Reinforcement of Concrete and Soil , Journal of Polymer-Plastics Technology Engineering, Vol. 38, No. 3, 533-546. 

---