The Influence of Waste Plastic Fiber on the Characteristics of Light Weight Concrete with Expanded Polystyrene (EPS) as Aggregate

T his research aims to create lightweight concrete mixtures containing waste from local sources, such as expanded polystyrene (EPS) beads and waste plastic fibers (WPFs), all are cheap or free in the Republic of Iraq and without charge. The modern, rigid, and mechanical properties of LWC were investigated, and the results were evaluated. Three mixtures were made, each with different proportions of plastic fibers (0.4%, 0.8%, 1.2%), in addition to a lightweight concrete mixture containing steak fibers (0.4%, 0.8%, 1.2%), in addition to a lightweight concrete mixture. It contains 20% EPS. The study found that the LWC caused by the addition of WPFs reduced the density (lightweight) of the concrete mixtures because EPS tends to form more blocks, absorb water, and dry the mixture. While the increase in WPF content increased in compressive strength, as the compressive strength of the concrete mix containing (EPS) was only 13.6 MPa, the compressive strength increased to 17.6 MPa when WPFs were added. The addition of plastic also increased the bending resistance, where the bending resistance of the concrete mix containing (EPS) was only 2.26 MPa and increased to 2.66 MPa when (WPFs) were added.


INTRODUCTION
These beads are used to create lightweight packaging materials. Before the production of EPS blocks, EPS beads are produced in factories or on-site as round white gains (Wang and Miao, 2009). These granules are made of dissolved polystyrene and pentane and have fireretardant additives (ASTM C330/C330M-17a, 2017). They are non-biodegradable and chemically inert in water and soil (Horvath, 1994). Because of the closed cell structure, EPS beads have a low water absorption capacity (Rathan and Badwaik, 2015). They are compressible and come in a variety of shapes for different applications. Since geofoam blocks are unsuitable for filling irregular shapes and sizes, EPS geometry and bottom ash can be used as alternatives enhanced with natural fibers. Concrete is a mixture of mortars, aggregates, and separate (non-continuous) fibers. Making use of fiber is not a new concept; thatch was used to reinforce roasted bricks 3,500 years ago. Asbestos fibers were the first fibers used in concrete, around 1900, but they were discontinued due to health concerns. Steel, glass, carbon, polypropylene, plastic, nylon, and sisal were among the fibers used in concrete at the time. Ordinary concrete, due to a lack of tensile strength and tensile stress capabilities, requires reinforcement before it can be utilized as a construction material. To improve tensile and shear strength, concrete is typically reinforced with continuous reinforcing bars strategically placed throughout the structure. Whereas the fibers are used infrequently and randomly throughout the matrix (ACI commitee 544, 2002; Bentur and Mindess, 2006). Recently, industrial development, including the plastics industry, has accelerated. Since plastics have a long analytical life and pollute the environment, studies have focused on reusing recycled plastic waste (sustainable plastic) to create environmentally friendly concrete (Qasim et al., 2022). The increasing demand for new infrastructure facilities and buildings, as well as the world's population growth, indicates an increased consumption of resources, particularly in the form of more durable concrete, such as High-Performance Concrete (HPC) (Al-Hadithi and Allani, 2015). The first synthetic plastics were developed nearly a century ago. Then, rapid population growth leads to an unprecedented increase in plastic production. Plastic was used in strategic sectors, including wrapping, construction, mass transit, medical devices, and sports, due to its efficacy and competency. Increased plastic use leads to increased waste at the end of plastic use. Plastics are non-biodegradable materials that accumulate in landfills because the moiety used in the petrochemical industry, such as both ethylene and propylene, are  Table 1. In all mixes, natural gravel with a nominal aggregate size (5-10 mm) was used as coarse aggregate. I grew up in the Spring neighborhood. The physical and chemical properties of the used aggregate, as shown in

Expanded Polystyrene Beads (EPS)
This study used spherical EPS beads with a maximum nominal size of 10 mm as a complete replacement for coarse aggregate. The gradient and physical properties of EPS beads are shown in Table 4 and Fig. 1. In this work, reinforcing fibers were made from PET bottles of a crystalline carbonated beverage that had been cleaned to remove impurities and shaped into strips. These pieces were then cut into 4 mm wide pieces in length using a paper shredder. Table 5 and Fig. 2 show the PET fibers' physical properties.

Molds, Mixing, and Casting
To determine the bending strength, three (100*100*400) mm prismatic molds were prepared for each age (7, 14, and 28). Three cube molds (100*100*100) mm for each age (7, 14, and 28) were prepared to test the compressive strength. The interior surface of the mixer was cleaned and wet before depositing the materials. The raw components were combined and allowed to dry for around three minutes to ensure that the polystyrene was evenly distributed throughout the mixture. After PET has been added, Water is added to the mixture, and mixing continues until a homogenous and flowing liquid is achieved. The mixing procedure takes roughly three minutes to produce homogeneous and uniform concrete. In the concrete lab of the Baghdad College of Engineering, all concrete was mixed using a planetary mixer (see Fig. 3). To enhance compaction and lessen the number of air bubbles, the mixture was put into oiled molds, which were then vibrated on a vibrating table for one minute. The samples were degassed after 24 hours and kept in water for processing before testing.

Concrete Mix
Three distinct concrete mixes, in addition to the reference mix, were employed in this study. Table 7 displays the percentage of the prepared concrete mixes.

Compressive Strength
Results of strength properties at (7, 14, and 28) days for all LWC mixtures are shown in Table 8 and Fig. 4. The addition of WPF in different volume ratios has a positive effect on the compressive strength. All blends containing WPF have higher pressure resistance than the reference mixture. This increase can be attributed to the fact that WPFs are uniformly distributed within the concrete mixture structure, which increases homogeneity and reduces the amount of voids within the concrete body, resulting in a more cohesive and rigid concrete body.  When microcracks form within the matrix, WPFs attempt to stop and limit the spread of these cracks in the adjacent development. As a result, the crack propagation path is wound, which requires more energy to continue crack propagation, and therefore this process must reach high pressures for the presence of failures (Ganesh and Saradhi, 2003). increase can be attributed to the fact that WPFs are regularly distributed within the structure of the concrete mixture, which increases homogeneity and decreases the amount of voids within the concrete body, resulting in a more cohesive and hard concrete body. When microcracks form within the matrix, WPFs attempt to halt and limit the spread of these cracks in the neighboring region's development. As a result, the path of crack propagation is wound, requiring more energy for continued crack propagation, and thus this operation must reach high stresses for the existence of failures, as shown in Fig. 5 and Table 9.

Density
As shown in Fig. 6, curing ages influence density for various concrete types, and testing results reveal that concrete has a significantly lower density than a control concrete mixture without plastic. Because PET has a lower unit weight, adding it to the mix reduces the unit weight of the mix for a specific age. Table 10 compares the results of LWC concrete to the control mix.

CONCLUSIONS
This work is concerned with using plastic wastes in concrete as fibers and replacing EPS granules instead of coarse aggregates. This approach is one of the effective methods to eliminate the bad environmental effects of these wastes and to improve some of the properties of concrete. Based on the analysis and discussion of the obtained results in this study, the following conclusions can be drawn: 1 -Adding WPFs with different volumetric rates to LWC improves compressive strength. When WPFs were added by volumetric ratio, the maximum increase in compressive strength ranged between (14.3) and (17.6) compared to the reference mix. 2 -When WPFs are added to LWCs at different volumetric rates, the rupture modulus of the LWC reinforced with these fibers increases when compared to the reference mixture. 3 -Lightweight concrete using EPS as coarse aggregate with different contents of WPF showed that the density of LWCFRC decreased, with increased contents of WPF in the concrete mixtures revealing lower density. 4 -According to the results of this study, the optimal PET fiber content in LWC could be 1.2%.
However, adding PET fibers with moderate to high content (0.4% to 1.2%) may be acceptable to avoid further workability loss and improve the LWC's properties.