Mechanical and Thermal Performances of Eco-Friendly Mortar Containing Recycled PET As Partial Sand Replacement

: Plastic has become one of the most widely manufactured materials in the world and an indispensable part of everyday life. However, a large amount of plastic waste needs to be recycled to protect the environment. One way of recycling is to use such waste as a raw material substitute. This paper evaluates the thermal and mechanical performance of eco-friendly mortars containing 0%, 5%, 10%, 15% and 20% recycled polyethylene terephthalate (PET) particles as partial replacements for sand. Several experiments were conducted to evaluate the thermal properties (i.e. thermal conductivity, thermal diffusivity and heat capacity), compressive strength, density, workability and ultrasonic pulse velocity of these mortars. Results show that replacing sand with recycled PET in cement-based mortars reduces their thermal conductivity, thereby highlighting the potential use of these mortars 21 as energy-efficient and environmentally friendly construction materials.

workability of plastic concrete with regular and irregular particle plastic waste aggregates and found that the 54 workability of regular particle plastic waste concrete is worse than that of irregular particle plastic waste concrete 55 and that its optimum compressive strength at 28 days was only 24% of irregular particle plastic waste. Almeshal 56 et al. (2020) studied how partially replacing sand with PET waste affects the fresh weight of the mix, the quality 57 of the concrete and its fire behaviour. They found that increasing the PET replacement rate in concrete reduces the 58 fresh weight values of the mix below the reference, the ultrasonic impulse velocity (which reflects the quality of 59 the concrete) and the fire resistance of the concrete; moreover, the addition of PET emits an unpleasant toxic 60 smoke. Steyn et al. (2021) examined the performance of concrete with waste plastic, rubber and glass as fine 3 aggregates at 15% and 30% replacement proportions and found that the addition of rubber and plastic leads to poor 62 durability and stiffness whereas the addition of glass improves durability and stiffness. By contrast, the concrete 63 with low plastic content has a compressive strength comparable to that of the reference mix but shows inferior 64 tensile performance, whereas the concrete with rubber demonstrates inferior compression and flexion at both high 65 and low contents. In sum, plastic waste can be used to produce building materials with acceptable engineering 66 properties.

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This paper then investigates the compressive strength and thermal performance of mortars containing 0%, 5%, 68 10%, 15% and 20% crushed recycled PET particles as partial replacements for sand. The correlation between the 69 mechanical and thermal properties of the concrete was also evaluated. This study aims to develop and promote the 70 use of sustainable and ecological mortars in thermal insulation.

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The mortars were manufactured using sea sand collected from the Kenitra region.

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The PET used as partial replacement for sand in a cement-based mortar ( Fig. 1) was recycled from washed and 92 crushed PET bottles and had a maximum particle size of 7 mm. systematically replaced with 0%, 5%, 10%, 15% and 20% PET particle mass as shown in 105 Table 3. A constant water/cement (W/C) ratio of 0.5 was observed when producing the mortars.

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Recycled PET Prismatic samples of (40 40 160) mm and (40 80 120) mm were made for each mix. A day after casting, the (40 107 40 160) mm prismatic specimens were stored in water at 21±1 °C, and the (40 80 120) mm specimens were stored 108 in ambient air until reaching the test age. 109

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The improved workability can also be ascribed to the shape and size of the PET particles, which is consistent with

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Thermal conductivity was correlated with density and UPV, respectively, as shown in Fig. 11. An exponential 236 correlation with a coefficient of 0.999 and a pre-exponential factor of 0.00003 was observed between thermal 237 conductivity and density as shown in Fig. 11 (a). Meanwhile, Fig. 11   samples decreased by 11%, 16%, 20% and 27%, respectively, after 28 days of curing. Such reduction 298 was mainly attributed to the low cohesion between the texture and the recycled PET, which acts as a 299 barrier that prevents the cement paste from adhering to the natural sands. 300 (5) Thermal conductivity, specific heat and thermal diffusivity are the most important thermal properties of 301 a mortar. Replacing 20% of sand with recycled PET decreased thermal conductivity by 47% and specific 302 heat by 39% and increased thermal diffusivity by 13%. The thermal behaviour of the mortar is directly 303 related to its composition. Meanwhile, the lower thermal conductivity of the inclusions that replace the 304 conventional components corresponds to a greater insulation efficiency. These improvements in thermal 305 properties were ascribed to the recycled PET that limits heat flow. Another factor that explains the 306 reduction in thermal conductivity is the increase in the number of voids, which subsequently increases 307 the amount of trapped air. The ability of materials to store heat is determined by their specific heat 308 capacity, whereas thermal diffusivity characterises the heat transfer abilities of materials. An eco-friendly 309 mortar containing recycled PET is a less conductive mortar that does not allow heat storage.