Use of a kaolinitic-illitic clay from Central African Republic and an organic waste for the production of porous ceramic materials

Abstract

This work aimed at investigating the use of agricultural waste for the manufacture of porous ceramic products while promoting the valorization of local clay materials. The peel of plantain (Musa paradisiaca) fruits appeared as potential porogen and source of flux during the firing of silicate ceramics. A commercial kaolin served as the reference raw clay to investigate the influence of the waste content (from 0 to 30 mass%) over the microstructure and mechanical properties upon sintering at 1000 and 1200°C (dwelling time of 1 hour). The main physical and chemical characteristics of the local clay (from Central African Republic) were analyzed. This clay appeared to be a moderately plastic silica-rich clay material that exhibited a bimodal particle size distribution. Mixtures of this clay with 0, 10, and 15 mass% of the waste were submitted to compressive strength testing upon firing at 1100°C (dwelling times = 1 or 2 hours). In all samples, the compressive strength decreased while the open porosity rate increased with increasing waste content. When using the commercial kaolin, the open porosity could be tuned close to 53% and 40% after firing at 1000 and 1200°C, respectively, by adding 30 mass% of waste. Accordingly, firing at 1200°C for the latter sample led to higher compressive strength due to the enhanced consolidation related to flux oxides arising from the waste burnt out. For the local clay, the incorporation of 10 or 15 mass% of waste led to open porosity values in the range 36%-40% after firing at 1100°C regardless of the dwelling time. Accordingly, the compressive strength was decreased, 60% of the initial value for the local clay without waste.