Influence of nano graphite platelets on the behavior of concrete with E-waste plastic coarse aggregates

Abstract

Past works have used electronic waste (E-waste) plastic as a raw material for the production of plastic aggregate to be used as a substitute for natural aggregates. However, the results have shown that the plastic aggregate reduces the strength properties of resulting concrete limiting its application to non-structural components. Nano graphite platelets (NGPs) are nanofillers that significantly improve the density and hardness of the cementitious composite due to reduction in porosity and reinforcement in microstructure. In the current study, NGPs have been utilized to increase the strength of plastic concrete. The natural coarse aggregates are partially substituted by 25% of E-waste plastic coarse aggregate. Locally available NGPs are utilized, and their structural characteristics were assessed by scanning electron microscopy (SEM), X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), and energy dispersive X-ray (EDX) spectroscopy. A dispersion test is carried out and a ratio of 0.6:1 (surfactant:NGPs) is found to yield maximum dispersion. Different dosages of NGPs (1%, 3%, and 5%) have been introduced into plastic concrete. This research work aims to explore the fresh, mechanical, durability, and microstructure characteristics. The mechanical properties of the cementitious composites declined with the incorporation of E-waste plastic aggregates which were significantly enhanced by incorporating NGPs. The specimens containing 25% of plastic aggregate and 5% of NGPs showed the hardened density, compressive strength, tensile strength, and flexural strength to increase by 2.16%, 13.56%, 15.53%, and 31.42%, respectively compared to the samples without NGPs. Sorptivity and ultrasonic pulse velocity values are found to decrease by 56.5% and increase by 2.53%, respectively for plastic concrete with 5% NGPs compared to the control mix. SEM-EDX spectroscopy was carried out to examine microstructure investigation and it was found that by the inclusion of NGPs in the concrete composites, the hydrated crystals stacked one over the other and became massive and thicker implying that the addition of NGPs is a promising reinforcing agent in plastic concrete.