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.

RESUMO Os materiais de isolamento térmico convencionais, tais como a lã de vidro e o poliestireno extrudado, possuem importantes limitações técnicas. Os geopolímeros emergem como uma alternativa devido às suas excelentes propriedades. Neste trabalho, teve-se por objetivo descrever o desenvolvimento de geopolímeros de baixa condutividade térmica. Na produção dos geopolímeros utilizou-se metacaulim (Al2O3.2SiO2) que, devido à sua elevada reatividade, permite produzir polímeros inorgânicos, com propriedades físicas interessantes para aplicações em isolação térmica. Amostras de aluminossilicato foram ativadas com hidróxido de sódio (NaOH) e silicato de sódio (Na2SiO3). Amostras de geopolímeros leves foram produzidas com adição de diferentes percentagens de um formador de poros (0,5, 1, 2, 3, 4%). As amostras produzidas foram caracterizadas quanto à: resistência, compressão, absorção de água, condutividade térmica, densidade aparente e microestrutura.

ABSTRACT Conventional thermal insulation materials, such as glass wool and extruded polystyrene, owned-in significant technical limitations. The geopolymers emerge as an alternative due to their properties. In this sense the objective of this work is to describe the develop geopolymers with low thermal conductivity. Samples of geopolymers were produced from metakaolin (Al2O3.2SiO2) which, due to its high reactivity, made it possible to produce inorganic polymers with interesting physical properties, which can be used for thermal insulation. The samples of aluminosilicate were activated with sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). Samples of light geopolymers were produced with addition of different percentages of a pore former (0.5, 1, 2, 3, 4%). The samples were characterized with respect to: compressive strength, water absorption, thermal conductivity, density and microstructure.

Red mud, the main waste generated in aluminum and alumina production by the Bayer process, is considered hazardous due to its high pH, according to the Brazilian standard NBR 10004/2004, and worldwide generation of this waste exceeds 117 million tons/year. In this work, non-calcined red mud was used, thus requiring less energy and time and reducing costs, which is the ideal condition for reusing wastes. Mortars containing 30 wt. (%) of cement substituted by red mud showed higher strength of hardened products. The pozzolanic activity index was evaluated based on physical and mechanical parameters (Brazilian NBR 5751 and NBR 5752 standards) and on a chemical analysis (European EN 196-5 standard). A comparison of the reference mixture (without red mud) and the results obtained with red mud confirm the potential of non-calcined red mud for use a as pozzolanic additive in cementitious materials. The setting time (according to the MERCOSUL NM 65 standard) tends to increase but workability remains almost unchanged.

Red mud, which is a solid waste produced in the alumina production process, is classified as dangerous due to its high pH. In this work, the concentration of chlorides was monitored by measuring the conductivity of the anolyte, which initially was distilled water. The steady and nonsteady-state chloride diffusion coefficients were estimated from the "time lag"� and "equivalent time" between diffusion and migration experiments. The capillary water absorption, apparent porosity and pore size distribution of concretes were also analyzed. The addition of red mud apparently ensured lower chloride diffusion in the tested mixtures due to its superfine particle-size distribution and its "filler"� effect. Red mud lengthened the service life of the concrete to 35 years (double that of the reference concrete). This finding is very positive since it indicates a delay in the onset of the rebar corrosion process caused by the migration of chloride ions.