Obtenção de cerâmicas quimicamente ligadas a partir de resíduos industriais

Abstract

Resumo Neste trabalho investigaram-se cerâmicas quimicamente ligadas com quatro resíduos industriais: areia de fundição, casca cerâmica, escória de níquel e tijolo refratário MgO-C. O sistema foi composto (% em massa) por 17% de fosfato monopotássico, 12% de magnésia cáustica e 71% de resíduo. Foram empregados três tempos de cura (1, 7 e 28 dias). A fase K-estruvita foi identificada por difratometria de raios X e microscopia eletrônica de varredura. A resistência à compressão aumentou com o tempo de cura, variando entre 7 e 17 MPa. As formulações contendo casca de cerâmica e escória de níquel, no entanto, apresentaram os melhores resultados devido à maior densidade relativa apresentada e aos cristais em forma de placa nas microestruturas obtidas. Os resultados mostraram ser possível a incorporação de resíduos industriais para a obtenção de cerâmicas quimicamente ligadas usando-se a técnica de cimento ácido-base.

Chemically-Bonded Magnesium Phosphate Ceramics from Magnesium Oxide-Graphite Refractory Brick Waste

“…As expected, the smaller the D mean the higher the specific surface area, ranging from 6.48 m 2 /g for the coarser powder to 14.36 m 2 /g for the thinner powder. Cárdenas Balaguera and Gómez Botero 6 studied the use of steel slag with D60 ranging from 200 to 230 µm to obtain chemically bonded phosphate ceramics, while Luza et al 13 used Mg-O refractory brick waste with D 50 of ~29 µm. Therefore, possibly greater powder reactivity may have been obtained related to the powders used by Cárdenas Balaguera and Gómez Botero 6 and Luza et al 13 .…”

“…The compositions studied were defined based on the stoichiometric composition of the isomorphic phase of K-struvite (Equation 1). However, KDP saturation in composition 13 produced interesting results over a certain particle size range and the KDP/waste ratio studied. Thus, considering the work of Luza et al 13 , specimens were obtained from KDP levels of 20-40 wt.% and three particle size ranges of the waste: between 180 and 250 μm (W1), 105 and 150 μm (W2), and 45 and 90 μm (W3).…”

“…The materials were weighed on a laboratory scale (MARTE model BL 3200H, Brazil; accuracy of 0.1 g). After weighing, KDP and W were properly mixed and homogenised in mineral water (250 mL) at room temperature, according to the procedure adopted by Luza et al 13 Each composition was mixed for 5 s with the aid of a metal rod, for its quick grip, and deposition in the PVC mould. Five specimens of each established experimental condition were prepared (Table 1) and demoulded after 24 h at room temperature.…”

“…In aqueous media, the acid-base reaction, which occurs between MgO and monopotassium phosphate, results in the formation of a crystalline structure, K-struvite (MgKPO 4 .6H 2 O), known as ceramicrete 13 .…”

“…Viani and Gualtieri 8 used monopotassium phosphate (KDP, KH 2 PO 4 ) and obtained the isomorphic phase of K-struvite according to the reaction of Equation 1 13 :…”