Impact of adding waste polyethylene (PE) and silica fume (SF) on the engineering properties of cement mortar

Abstract

The production of plastics and subsequent accumulation of plastic waste has escalated as a direct consequence of rapid population growth and urbanization. Within this framework, research on the recycling and repurposing of plastic waste in the construction sector offers a means to mitigate the adverse environmental effects of plastic waste and save natural resources. This study examined plastic fine aggregates (PFA) produced from polyethylene (PE) as a substitute for natural fine aggregates in mortars. Mortar mixes were created and tested with varying percentages of PE as a substitute for natural sand: 2.5 %, 5 %, 7.5 %, and 20 %. In addition, varying percentages of SF as a substitute for cement were 10 % and 20 %, respectively. The study of fresh properties focuses on workability and setting time, whereas the study of mechanical properties focuses specifically on compressive strength. The findings demonstrated that using the produced PE enhances the malleability of concrete, and it was anticipated that this would result in a significant decrease in compressive strength. To improve the strength characteristics, silica fume (SF) was added to the concrete mixture as a substitute for cement, using the same ratio of replacement as for PE. The inclusion of silica fume mitigated the impact of the plastic aggregate on the strength characteristics, resulting in a decrease of only 8 % in the compressive strength of the mortar when the plastic aggregate was entirely replaced with silica fume. The findings show that the optimum mix can substitute 10 % natural sand with plastic sand while maintaining the compressive strength by adding 20 % silica fume. In summary, the findings indicate that plastic aggregates may substitute natural fine aggregates to create an environmentally friendly mortar with similar strength characteristics.