Recycling and Valorisation of Industrial Wastes In the Formulation of a Sanitary Ceramic Body

Abstract

The research work conducted aims at the valorisation of solid industrial waste by its incorporation in the composition of sanitary ceramic bodies.This thesis is divided into three sections: In the first, we investigatethe effect of the substitution of feldspar by blast furnace slag (BFS), on the properties of sanitary ceramic bodies.The use of Na-electrolytes at the optimum ratio Na2CO3/Na2SiO3=1.5 with a combined amount of 0.375 wt. %, is found effective to improve the rheological behaviour of the slip. The structural and morphological characterisation of these ceramic bodies were identified by XRD, SEM and FTIR spectroscopy analyses. Mullite and quartz are the main phases in the ceramic matrix with the gradual appearance of the anorthite phase. TGA/DTA analyses prove that there is no significant effect on the peaks of kaolin dehydroxylation and mullite crystallization.It was concluded that the inclusion of 10 wt. % BFS in the ceramic mixture represents the optimum composition as it increases the flexural strength from 33 to 38 MPa and reduces the water absorption from 0.35 to 0.10%. In the second section, we study the effect of the substitution of feldspar by soda-lime glass waste (SLGW) on the properties of sanitary ceramic bodies. The rheological behaviour of the slip is improved by SLGW addition using a small amount of electrolytes (0.075 wt. % Na2CO3 and 0.1 wt. % Na2SiO3). XRD, SEM and FTIR spectroscopy analyses show that mullite and quartz are the main phases in all ceramic bodies with a slight appearance of the anorthite phase. TGA/DTG analyses prove that there is a reduction of mass loss during the addition of SLGW. It was found that the addition of 20 wt. % SLGW in the ceramic composition increases the Bulk density (2 to 2.52 g/cm3) and reduces water absorption (0.35 to 0.02%). In the last, we focused on the recycling of the sanitary ceramic waste (SCW) in the formation of its unglazed bodies. The different slips containing SCW, have optimal properties when adding a combination ofelectrolytes at ratio Na2CO3 / Na2SiO3=0.25, with a total combined amount of 0.375 wt. %. XRD and FTIR analyses show the high intensity of quartz and mullite in bodies containing SCW.The VC5 body (5 wt. % SCW) has the best physical-mechanical results as it has a flexural strength of 44 MPa and a water absorption of 0.18 %. Moreover, the VC10 body sample has better physical-mechanical properties than the standard ceramic sample. Therefore, SCW can be recycled and incorporated in the manufacture of their unglazed bodies up to 10 wt. %.