Compressive Behavior and Durability Performance of High-Volume Fly-Ash Concrete with Plastic Waste and Graphene Nanoplatelets by Using Response-Surface Methodology

Plastic waste (PW) generation continuously increases every year due to the growing population and demand for plastic materials. This situation poses a challenge to many countries, including developed ones, on how to dispose of PW. Accordingly, PW was utilized in this study to replace coarse aggregates partially in high-volume fly-ash (HVFA) concrete. However, PW decreased the strength and durability of concrete. To address this issue, graphene nanoplatelets (GNPs) were added to mitigate the negative consequences of PW and HVFA on concrete's properties. The objective of this study is to investigate the influences of PW and GNP contents on the durability and deformation of HVFA concrete. Response-surface methodology (RSM) was used to design and optimize a series of cement mixes to achieve the most desirable properties. Independent variables included PW content as partial replacement for coarse aggregates (0%, 15%, 30%, 45%, and 60% by volume), fly ash as partial substitute for cement (0%, 20%, 40%, 60%, and 80% by volume), and GNPs as additives (0%, 0.075%, 0.15%, 0.225%, and 0.3%). The considered responses were concrete unit weight, modulus of elasticity (MoE), and Cantabro abrasion loss at 300 revolutions. Results showed that PW and HVFA decreased concrete unit weight and MoE but increased Cantabro abrasion loss. By contrast, GNPs increased concrete unit weight and MoE but decreased Cantabro abrasion loss. PW and HVFA also increased the compressive toughness and porosity of concrete, while GNPs increased its stiffness but decreased its compressive toughness and porosity. The mathematical models developed to predict the unit weight, MoE, and abrasion resistance of concrete were significant, with errors of less than 6%. An optimized mix was achieved by partially replacing 12.44% of coarse aggregates with PW and 24.57% of cement with fly ash and adding 0.279% GNPs with a desirability of 100%.

Automated summary

Plastic waste has a negative impact on the strength and durability of concrete, and the addition of graphene nanoplatelets can mitigate this effect.