Experimental Study on Cementless PET Mortar with Marble Powder and Iron Slag as an Aggregate

There has been an increase in plastic production during the past decades, yet the recycling of plastic remains relatively low. Incorporating plastic in concrete can mitigate environmental pollution. The use of waste polyethylene terephthalate (PET) bottles as an aggregate weakens properties of concrete. An alternative is to use PET bottles as a binder in the mortar. The PET binder mixed with sand results in weak mortar. Marble and iron slag can enhance PET mortar properties by preventing alkali reactions. This study examines the mechanical and durability properties of PET mortar with different mixes. The mixes were prepared as plastic and marble (PM); plastic and iron slag (PI); plastic, sand, and marble (PSM); plastic, iron slag, and marble (PIM); and plastic, sand, and iron slag (PSI). PM with 30–45% plastic content had increased compressive and flexural strength up to 35.73% and 20.21%, respectively. PI with 30–35% plastic content showed strength improvements up to 29.19% and 5.02%, respectively. However, at 45% plastic content, strength decreased by 8.8% and 27.90%. PSM, PIM, and PSI specimens had nearly double the strength of ordinary Portland cement (OPC) mortar. The durability of PET mortar in chemical solutions, mainly 5% HCl and 20% NaOH, indicate that mass decreased after 3, 7, and 28 days. All specimens showed good resistance to HCl and NaCl solutions compared to OPC mortar. However, its resistance to NaOH is low compared to OPC mortar. PET mortar without cement showed higher strength and durability than cement mortar, making it suitable for paver tiles, drainage systems, and roads.