Plastic waste utilization as macro fiber in concrete

Abstract

The use of plastics has increased over the years, thus resulting in a large volume of plastic waste being generated and accumulated in the environment. Due to its non-biodegradability and persistence, recycling processes have become one of the sustainable solutions for preventing environmental deterioration. Plastic wastes, including high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), and polyethylene terephthalate (PET), were collected from industrial sector and used as additional ingredients (macro fiber) to improve mortar properties. Prior to mortar processing, an increase in wettability of plastic fibers using nonionic surfactant, Dehydol LS-12, was investigated. At the optimal concentration of 10 times of the critical micelle concentration (CMC), an interfacial tension and a contact angle were reduced to 31–32 mN/m and 65–68 degree, respectively. Properties of synthetic fiber reinforced mortar were determined and compared to those of the conventional mortar samples. Porosity was found to increase ((-8%)-44%) with higher volume fraction of plastic fibers, whereas decreases in workability ((-91%)-52%), bulk density ((-14.7%)-(-0.3%)), thermal conductivity ((-31%)-(-2%)), splitting tensile strength ((-77%)-7%), and compressive strength ((-79%)-(-6%)) were encountered. The lowest thermal conductivity (-31%) was recorded for mortar samples prepared with 30% by volume of LDPE fibers, and the rest in descending order were HDPE, PP, and PET, respectively. The degradations of plastic fibers immersed in alkaline solution (7-180 days) did not reduce their tensile strength significantly while UV-A radiation could decrease their tensile strength with increase time exposure. Furthermore, the maximal inclusions of plastic fibers were 5% for HDPE and LDPE, 10% for PP, and 50% for PET so as to satisfy the precast concrete wall requirements.