# Effect of Adding Waste Polyethylene and GGBFS on the Engineering Properties of Cement Mortar
## 1 Introduction
Therefore, plastic waste's almost permanent pollution of the natural environment is a growing problem [15]  
Taiwan has the second highest density of convenience stores in the world [16], and most disposable food packages usually contain a plastic film [5] composed of polyethylene (PE), a high-quality material with resistance to impact, good chemical stability and resistance to low temperatures. Most single-use paper containers are considered plastic waste rather than waste paper. With the ever-increasing amount of plastic waste, recycling is an efficient way to reuse or recycle waste into useful products, materials, or components  
According to the Taiwan Environmental Protection Agency, in Taipei alone, takeout packaging increased by 85% in May 2021, which may be due to the impact of the COVID-19 outbreak. In general, recycled food packaging consists of different polymers and complex materials, making it difficult to separate each material [16]. The PE components in the packaging container must be separated by buoyancy separation and then recycled. Polyethylene (PE) is one of the most widely used polymers in the world [17]. One million plastic bottles are purchased every minute and this number is expected to increase by 20% by 2021 [18]. Due to the excessive use of this material, the problems caused by its waste are becoming more and more serious. In search of sustainable solutions for PE waste, research has been developed using waste as a constituent of concrete, mortar, and fly ash geopolymer in recent decades [19; 20; 21; 22; 23; 24; 25; 26]. Based on the concepts of sustainable construction and the past results obtained in the research analyzed. The use of PE waste as a substitute in natural mortar sand has become an interesting option to reconcile the reduction in the use of natural aggregates and the reuse of non-biodegradable waste [4]. Researchers have studied the inclusion of recycled plastic waste in building materials such as bricks and concrete [27; 28]. In addition, recycled plastic waste can also be used in plastic-wood building materials when combined with wood and other plant fibers [5]. In recent years, ordinary-strength concrete has not been able to meet performance demands for the increasing number of underground structures in complex geology [29]. This results in an improved global structural response of the composite, characterized by an increase in different mechanical properties, such as tensile and flexural strengths, ductility, toughness, and fracture energy [30]. In this study, adding GGBFS and waste PE materials to make cement mortar improves the usability of waste and green energy. Research indicates that PE fiber-reinforced CAC-GGBFS blended mortar provides improved durability against sulfuric acid attacks, adding longevity and decreasing the maintenance costs of concrete sewage pipes [31; 32]. Past studies have shown that recycled plastics can replace fine aggregate and add mortar [33]. However, as the discarded PE in the mix increases, the bulk density of the mortar in the hardened state decreases. This reduction is due to the fact that the density of plastic aggregate is 70% lower than that of natural sand [34]. The water absorption of the mortar increases with the content of waste PE because the addition of waste PE induces the balling phenomenon, which increases the internal porosity of the specimen, and the water absorption rate increases with the content of the PE material. When 20% sand was replaced by low-density polyethylene (PE), the overall density of the mortar decreased by 10% and the water absorption increased by 11.5% [35]. The measured value of the velocity of the ultrasonic wave has a considerable relationship with the compactness of the cement products. [PERSON] et al. observed a reduction in the speed of the ultrasonic pulse in mortar samples due to the increase in the aggregate of waste PE in mortars [36]. [PERSON] et al.