Estabilização de areia descartada de fundição com um ligante alternativo de cinza de casca de arroz e cal de casca de ovo hidratada

Abstract

Waste foundry sand (WFS) is a by-product generated in large quantities by the metal foundry process. This material requires disposal in an industrial landfill, it makes costly for industries and can be cause impacts to environment. The ADF reuse commonly occurs through cementing agents, such as Portland cement. However, the conventional cement production requires high energy demand, high consumption of natural resources and generates greenhouse gases, which justifies searching for alternative binders. Industrial wastes as Rice husk ash (RHA) and eggshells recycled as hydrated eggshell lime (HEL) have great potential for WFS stabilization through pozzolanic reactions. The objective of this work is to applicate of the alternative binder from rice husk ash (source of amorphous silicates) and hydrated eggshell lime (source of calcium) for ADF stabilization, with the aim to study the mechanical behavior and leaching and solubilization of metals. From initial tests and experimental planning, controllable factors were chosen to analyze their influence on unconfined compressive strength (USC). It was found that higher USC values are obtained with an increase in the binder content and a higher dry specific weight of the mixture, with a strength of 1.69 and 2.41 MPa for 28 and 90 days of curing, respectively. The factors that had highest influence on the USC of the WFS-binder mixtures are, in this order: CCA content; dry specific weight and curing time. The results of leaching and solubilization of metals showed that the ADF-binder mixture with 28 days of curing and better mechanical behavior (30% of RHA and 15 kN/m³) did not present toxicity and solubility by metals. In this way, it encapsulated Al, Fe and Zn present in the residues (WFS and RHA).