Avaliação das propriedades técnicas do concreto convencional com substituição parcial da areia por resíduos de casca de ovo

Abstract

Civil construction uses approximately 40% to 70% of the natural resources on earth, and therefore, it is one of the sectors that cause the greatest environmental impact due to the high consumption of raw materials. Several studies present the impacts generated by the construction industry on the environment and therefore, the model adopted in the current scenario must consider human development, technological innovation, the balanced use and reuse of available natural resources and the reinsertion of waste in the production chain, according to the circular economic model. The eggshell has in its composition a limestone layer, composed mainly of calcium carbonate for the most part (about 96%), magnesium carbonate and calcium phosphate, in smaller amounts. Its use in the production of concrete, in addition to favoring the destination of a residue, contributes to the increase of the porosity of the concrete, providing greater capture of CO2. In this study, 3 types of specimens were manufactured, where the sand was partially replaced in unit volume, by eggshell, in the percentages of 5, 10 and 20%. Mechanical tests showed a drop in compressive strength values, which can be corrected by reducing the water/cement ratio from 0.60 to 0.40. There was also a greater resistance to impacts of concretes replaced with eggshells in the order of, notable for the smaller depth and smaller area of influence of projectile impacts. The thermogravimetric curves indicated a greater potential for CO2 capture by concrete incorporated with eggshell. There was also an increase in the porosity of the eggshell concrete, as evidenced by the reduction in density, increased water absorption and higher carbonation rate. In this way, the eggshell has potential for use in activities aimed at the production of concrete for non­structural purposes, attributing value to this solid waste and reducing the pressure exerted on nonrenewable natural resources, such as sand in this case. Finally, studies on the replacement of cement by eggshell are recommended, in order to verify the possibility of filling existing voids due to the porosity of the concrete, favoring the increase in strength combined with the other benefits already mentioned in this study.