**3. Final considerations**

At this sense, it is technically possible to recycle steel slag by incorporating into clayey ceramic. However, the incorporation of this waste into clayey ceramics must be done in amounts of up to 10 wt.%. An elevated amount of steel slag can increase the porosity of the fired ceramic and decrease its mechanical strength due to its inert action and elevated weight loss.

It can be concluded by the influence investigation of the steel sludge as raw material for ceramic production in that its incorporation is technically feasible. The porous agglomerate constituents of the steel sludge do not adhere to the clayey matrix, creating regions of failure that contribute to the reduction of the mechanical strength of the final products with incorporations of residue above 5% by weight. The environmental evaluation shows excess of Al in the solubilization extract, coming from the clay. The other evaluated elements are within the limits required for both the solubilization tests and the leaching test. The fine steel sludge is a waste predominantly composed of Fe metallic, Fe oxides (magnetite and wustite), and calcium carbonate (calcite). This waste shows a fine particle size, average of 35.6 μm that is appropriate for red clay-based ceramic production. This waste contributes to increase the dried bulk density of the ceramic. Incorporations of 5 wt.% of the waste are beneficial to the ceramic since it decreased the fired linear shrinkage and does not increase the water absorption. And also, the mechanical strength does not decrease which is also a convenient result for this level of incorporation.

The incorporation of a particulate, PMW, waste generated in the sintering stage of an integrated steelmaking plant, caused significant changes in a kaolinitic clay-based ceramic sintered at 1050°C. Relatively large dark phases associated with Fe and Ca compounds in the waste were formed in the clayey ceramic matrix. These phases showed evidences of microcracks- and pores-induced defects. The PMW incorporation results not only in an increased amount of porosity but also pores with relatively larger sizes. It is suggested that the inert nature of the waste, as well as its different coefficient of thermal expansion with respect to the aluminum silicate matrix, is responsible for the additional defects produced in the clayey ceramic. It was found that the particulate material waste from the sintering stage of an integrated steelmaking plant has an elevated amount of Fe and Ca compounds. The incorporation of this waste, in amounts of up to 20 wt.%, into a clayey body did not change its workability and enhanced the evaluated physical and mechanical properties such as water absorption and flexural rupture strength. The results indicated that this type of waste has a potential to be used into red ceramics with real benefits both in the processing and in the quality of the products.
