Abstract In Brazil, the production of each ton of steel generates approximately 621 kg of waste and direct co-products. One of the components that generates a high amount of waste is the refractory material used in the steel process. So, in this study, the possibility of using MgO-C refractory waste from steel casting pots after their deterioration for the formation of chemically bonded phosphate ceramics was investigated. This work aims to study the recovery of industrial solid waste from MgO-C refractories by determining the processing conditions necessary to obtain magnesium phosphate ceramics. Three mean particle size of the waste and three potassium monophosphate:MgO ratio in the mixture were adopted. All mixtures showed the formation of the K-struvite phase and a strong relationship between the compressive strength and porosity properties. The highest compressive strength value obtained, 7.51 ± 0.24 MPa, is sufficient for use in several areas of engineering. It was also possible to statistically represent, using a quadratic model, the variation in porosity in relation to the phosphate content and particle size of the waste, obtaining porosities ranging from 14% to 25%. Taking into account this study used a waste, the evaluation of its environmental impact assumed an important role. The waste showed no appreciable toxicity, while some samples W3-20 showed toxicity to Allium cepa L. and Artemia salina. Considering the presented properties, the obtained material could be used as a structural block, filters, support for catalysts, and repair element for cement-based structures and roadways.

ABSTRACT Waste generation is increasing in many industries. Therefore, effective measures are required to secure an environmentally sustainable and economically viable waste destination. Co-processing in clinker kilns at high temperatures and incorporation into cement matrices may stabilize many types of industrial waste. This paper presents the results of a study that characterized pulp and paper mill waste and their recycling in clinker production. Chemical characterization and estimation of the hazardous potential of lime mud, biomass ash, and wastewater treatment plant (WWTP) sludge were performed in accordance with brazilian standard (NBR) 10004:2004. Biomass ash and WWTP sludge were classified as non-hazardous (class II), while lime mud was classified as hazardous (pH > 12.5, class I). These wastes were mixed (69 wt % lime mud, 29 wt % biomass ash, and 2 wt % WWTP sludge), and the resulting mixture was processed at 1455 ºC to generate ‘Ecoclinker’. The clinker was characterized, milled, and mixed with calcium sulphate for use as an ‘Ecocement’. Mortars were obtained and cured for periods of seven and twenty-eight days. The hardened product exhibited a mechanical strength of ~20 MPa. The leaching and pH tests indicated that these parameters were within the permitted limits, confirming that this waste-based cement was non-hazardous.

RESUMEN La generación de residuos sólidos está aumentando en muchos sectores industriales; por lo tanto, se requieren medidas efectivas para garantizar un descarte de residuos que sea ambientalmente adecuado y económicamente viable. El coprocesamiento en hornos de producción de clínker a altas temperaturas, así como la incorporación en matrices de cemento, son estrategias utilizadas para estabilizar muchos tipos de residuos industriales. En este estudio se analizan los resultados de un estudio acerca de la caracterización de residuos de papel y celulosa y su reciclaje en la producción de clínker. La caracterización química y la estimación del potencial peligroso de lodo de carbonato, la ceniza de biomasa y el lodo de la estación depuradora de aguas residuales (EDAR) se realizaron de acuerdo con la norma NBR 10004: 2004. La ceniza de biomasa y los lodos de la EDAR se clasificaron como no peligrosos (clase II), mientras que el lodo de carbonato se clasificó como peligroso (pH > 12.5, clase I). Una mezcla de estos residuos (69 % en peso de lodo de carbonato, 29 % en peso de ceniza de biomasa y 2 % en peso de lodo de EDAR) fue procesada a 1455 ºC para generar el denominado Ecoclínker. El clínker fue caracterizado, molido y mezclado con sulfato de calcio para ser utilizado como Ecocement. Los morteros fueron obtenidos y curados por períodos de 7 y 28 días. El producto endurecido mostró una resistencia mecánica de ~ 20 MPa. Las pruebas de lixiviación y pH estuvieron dentro de los límites permitidos, lo que confirma el carácter no peligroso del cemento a base de residuos.

This paper presents an evaluation study of wastes from pulp and paper as well as construction and demolition industries for application in cement-based materials. The alternative raw materials were used as a source of calcium carbonate (CaCO3) and as pozzolanic material (water-reactive SiO2) in partial replacement of Portland cement. In addition to the hydraulic binder, coating mortars were composed by combining the pulp and paper fluidized bed sand residue with construction and demolition wastes, both added as small aggregates. Rheological and mechanical characterization showed that the waste additions changed the behavior of the cement materials, increasing both the viscosity of the pastes (at constant shear stress or rate). The formation of agglomerates in the cement hydration process made the mortars with additions of residues (lime and ash sludge) have an increase in the mechanical strength of the hardened bodies when compared to the mortar (M0W) prepared only with the residues (fluidized bed sand and C & D) as aggregates.