Influência do grafeno e dispersantes na hidratação, microestrutura e propriedades autolimpantes de matrizes cimentícias

Abstract

This study investigated the dispersion of graphene nanoplatelets (GNPs) and their impact on hydration, microstructure, mechanical properties, and self-cleaning capacity of cementitious matrices. The study was divided into three main stages: 1) determining the optimal stirring time for GNP dispersion with and without polycarboxylate (PCE); 2) analyzing the influence of the order of addition and stirring of PCE and GNPs on dispersion and stability; 3) evaluating the effectiveness of different PCEs in dispersing GNPs. The characterization of cement pastes included X-ray diffraction (XRD), thermogravimetry (TG/DTG), and scanning electron microscopy (SEM). The selfcleaning capacity was assessed through an accelerated microalgae growth test using Chlorella vulgaris as a model. The results showed that ultrasonic treatment effectively dispersed GNPs, and the order of addition influenced their dispersion. The ratio between GNPs and dispersant (g/d) of 1:3 or higher proved to be the most efficient. Initial hydration was delayed by the addition of GNPs, but when dispersed with PCE, GNPs accelerated hydration, especially in small quantities (up to 0.12%). After 120 days, samples with GNPs dispersed at a 1:1 ratio showed the highest hydration rate. Mechanical tests revealed that GNPs without dispersant reduced strength due to nanoparticle agglomeration, but PCE mitigated this effect, with an ideal g/d ratio of 1:1. In the selfcleaning tests, all samples with GNPs showed reduced microalgae growth, with efficacy varying according to the g/d ratio: 1:3 for 0.03% and 0.12% GNPs, and 1:1 for 0.21% and 0.30%. The homogeneity of GNPs on the sample surfaces correlated with self-cleaning effectiveness.