Transcript Slide 1
Mechanical properties improving of calcinated clay synthetic aggregates by crystalline ceramic phase development in conventional thermal treatment L. F. Berti, S. M. de Souza, D. M. Trichês, F. B. Laraz, C. A. Frota Particulate aggregates are common raw material within the Brazilian territory. Nevertheless, in the north Brazil the stone exploitation is not a widely feasible activity due to its deposits covering with a layer of sedimentary material. The Amazonic region fits to this situation and alternative materials were already studied in the literature with appropriated feasibility [1,2]. One alternative material is the ASAC, which is an aluminium silicate phase containing red ceramic. Author [3] addressed the production of crystalline ceramic phase from common minerals at temperature ranges consistent with the conventional clay ceramic thermal treatment. These minerals are abundantly available in the Amazonic region and present high quality in phase composition. This work focuses, therefore, mainly in proposing a feasible processing route based on the reactive sintering for improving the mechanical properties of ASAC by developing the crystalline phase. According to Y. Zhao et al. 2011, heating up kaolinite produces, in intermediate temperatures, mullite and amorphous silica: When T=400-500°C, 2SiO2.Al2O3 .2H2O… (kaolinite† ) ˆ2SiO2 .Al2O3 … (metakaolinite† ) +2H2O when T>980°C, 2SiO2.Al2O3 … (metakaolinite)† SiAl2O4 … (spinel)†+ ‡ SiO2 … (amorphous† ) or 2SiO2.Al2O3 … (metakaolinite)† Al2O3 … (γ-alumina† ) + 2SiO2 … amorphous† when T>1100°C, SiAl2O4 … (spinel)†+ SiO2 … (amorphous) 1/3.… (3Al2O3.2SiO2† )(mullite† ) + 4/3 SiO2 … (amorphous† ) Therefore, at high temperatures starting in 1100°C the product of kaolinite is mullite and amorphous silica. The idea behind this work is to adapt the conventional red ceramic manufacturing process in order to develop particular ceramic phase, which can improve the body mechanical property. This is a preliminary work, which intends to show the theoretical fundamentals for basing the idea. Mineral phase adding Raw Material Mixing According to C.Y. Chen et al. 2000, mullite may be produced by adding alumina in 42 wt.% at temperatures starting from 1200°C. Clay Water Chemical additives The main idea of this work is to produce mullite out of a mixture consisting of kaolinite and bauxite in temperatures lower than 1200°C, following the expression: Raw material When T < 1200°C, 2SiO2.Al2O3 .2H2O… (kaolinite† ) + (bauxite) 3Al2O3.2SiO2†(mullite† ) An highlight point, the amount of silica in the final product is to be minimized by balancing with bauxite content. extrusion Thermal treatment Ceramic brick Manufacturing process flowchart With vacuum help Up to 1200°C Conclusion: The production of a mullite ceramic phase by kaolinite and Al-rich minerals mixture is feasible, so the original ideal of this work is to test the production of mullite in red ceramic within the conventional manufacturing process cycle. Although the idea bases in preliminary results, in the literature there are several sources which corroborate for the successful of the work.