Estabilização de resíduo de areia descartada de fundição com agente cimentante a base de cinza-cal

Abstract

Industrial waste such as rice husk ash (RHA) have an excellent potential to use in mixtures with hydrated lime (HL) due to their ability to stabilize soils. Likewise, waste foundry sand (WFS) and carbide lime (CL) are types of industrial waste with high applicability in civil construction, both due to the high volume discarded and excellent physical and chemical properties. Byproducts such as WFS, RHA and CL are normally discarded in landfills, a fact that ends up causing high costs to industries, in addition to the high volume produced, also contributing to reduce the lifespan of landfills. The reuse of waste as raw materials aims to reduce environmental impacts and contribute to the search for a cyclical and sustainable economy. The purpose of this study is to produce pozzolanic reactions between RHA with CL or HL, and thus provide the chemical stabilization of WFS, acquiring strength and promoting the immobilization of possible contaminants present in the wastes. Through an experimental design, cylindrical specimens were produced to perform unconfined compressive strength tests (UCS) with variations of RHA (10%, 20% and 30%), dry specific weight (12.00; 12.75 and 13.50 kN/m³) and curing time (28, 60 and 90 days) with each type of lime (CL and HL). Solubilization and leaching tests, mineralogy and microscopy of the mixtures with better UCS results were carried out, as well as a self- healing test of mixtures with CC. The results showed that higher specific weights result in higher strengths. The percentage of RHA and curing time are non-linear variables, while specific weight is a linear variable. It was observed that the higher the percentage of RHA, the greater the UCS, a very positive fact for the application of larger amounts of RHA. The solubilization and leaching tests also had positive results, as all metals are below the limit of Brazilian legislation. The microscopy showed the formation of structures that resemble cementing gels (C-H-S), a fact also observed in the X-ray diffraction test (XRD). The proposed healing assay demonstrated an increase in stiffness after damage, stabilizing at 60 days. The proposed material with mixtures of three wastes has satisfactory characteristics for use in various applications in infrastructure works.