Thermochemical transformation of residual materials by synthesizing lightweight granulates

International audienceThe general scope of this concern is to explore the formulation and the production, by thermochemical transformations, of expanded lightweight granulates incorporating residual materials as industrial and sewage sludge, schists, kaolinic waste, wasted glass… Depending on their nature, these materials contain fluxes, calorific power substances and potential pollutants. The possible application fields are light concretes, road engineering, water treatment and hydroponic agriculture. The benefits can be multiple: create new resources from wastes; preserve alluvial resources, humid zones on the river banks and the natural course of rivers; manage hazardous residual materials.Tests on the thermal treatment and the thermochemical expansion were conducted in horizontal experimental set-up including a static electrical furnace. Raw mixtures and treatment products were examined by visible microscopy, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD) and infrared spectroscopy (IR). Data analysis of the experimental results showed the possibility of obtaining the expanded granulates at temperatures lower than 1200 °C for a firing time around 10 minutes. The optimal temperature for their synthesis is a function of fluxes content and decreased dramatically with increase of the wasted glass amount. Obtained granulates have a density lower than unity and they have a good mechanical strength fulfilling the conditions for their use as building materials.Sewage sludge, wasted glass as well as incinerator ashes can be used as alternative materials, among other industrial solid wastes, in the formulation of lightweight clay and schist based granulates. Results of this work try to meet the principles of sustainable development preserving both the resources and the environment