Efeito da adição de sienito nas propriedades de concretos: estudo das equações de empacotamento e propriedades tecnológicas

Abstract

Civil concrete is a composite obtained from the combination of coarse and fine aggregates, cement and water, and it is one of the cheapest and most easily produced materials in the world. Concrete’s cost and quality are normally associated to the proportion of its constituents (ceramic formulation), as well as the reduction of water consumption. The determination and optimization of concrete formulations is made through the application of mathematical models of packing and concrete dosage, like the methods ABCP and IPT/USP, which are practical methods used by civil industry, and Andreassen and Alfred, which are theoretical methods used by the ceramic industry. The aggregates used in civil concrete may have diverse origins, and there is a strand of research for the substitution of conventional aggregates by materials which cause impact to the environment. The syenite extracted at Maciço Alcalino da Pedra Branca is one of the materials that can be used for this substitution. Its current application is directed to ornamental rocks, and the reject is currently being accumulated in the environment, since the exploitation is low during extraction. Thus, this paper aims to investigate the addition of syenite as an aggregate in the formulation of concretes and its properties. In order to do so, the formulations of civil concrete were calculated and optimized using the mathematical models above mentioned, the properties of the product before, during and after final set-time were also evaluated. The formulation which obtained the best results was the one using Andreassen’s method. To this formulation were made the additions of syenite in the place of the fine aggregate, in the proportions of 25, 50, 75 and 100%. In order to maintain the original granulometric distribution, an algorithm was developed to compensate the different particle size distributions, reaching excellent results in the properties evaluated in fresh and hardened concrete. The grain size correction guaranteed the maintenance of the original properties of the concrete not only in substitutions using syenite, but also with other aggregates, such as scrap (sanitary ware disposal) and thermoset polymer. Even though all formulations guaranteed values of mechanical resistance above 35 MPa, which was the value established as mechanical resistance after 28 days, the formulation with 25% substitution presented the best results.