ABSTRACT
The urban heat island effect has become a critical issue in urban areas, intensifying heat-related problems and increasing energy consumption. A sustainable cement formulation that combines ordinary Portland cement (OPC) with a carbonated aggregate derived from Periwinkle shell powder for the development of an efficient cool material is presented. Through a carbonation process, the aggregate undergoes a transformation, capturing carbon dioxide (CO2) and converting it into calcite. The resulting cement mixture exhibits high solar reflective properties, making it a potential candidate for cool pavement and roof applications. In this study, the raw materials, including the Periwinkle shell powder, were characterized, and the carbonation process was evaluated to quantify the CO2 capture efficiency. Additionally, a real test of the efficiency of this new cement on a roof demonstrated that the material achieved a significant cooling effect, being 6 °C cooler than that with standard OPC at the peak of solar radiation.
ABSTRACT
Suspensions of nanometric-sized graphene platelets have been proposed recently as potential heat exchange working fluids, due to their remarkably enhanced thermal profile. Nevertheless, their use presents serious long-term stability issues. Due to this limitation, the nanoplatelets surface chemical functionalization has been postulated as a promising alternative to solve this problem. In this work, graphene nanoplatelets were functionalized following an oxidation-reduction process, and then dispersed in glycol as base fluid. The nanoparticles chemical profile was determined using XPS (x-ray photoelectron spectroscopy). The thermo-physical properties characterization of these nanofluids was performed by determining their viscosity and thermal conductivity, because of their impact on practical applications related with fluid flow and heat transfer. The effect of temperature and shearing time on viscosity were analyzed. Viscosity was measured with a stress-controlled rheometer. All samples show shear-thinning behavior with a very remarkable influence of temperature in their viscoelastic profile.
