Waste sludge generated in the potabilization of surface water is used to produce cellular materials by mixing with clay and firing at 1 250C. An iron-rich glassy matrix with crystals of mullite and albite is formed. Porosity is generated by the slow release of H 2 O, which originates from the dehydroxilation of lepidocrocite at high temperature. The sludge/clay ratio and the sludge granulometry determine the properties of the product: from highly porous cellular foams to denser materials with high strength. Laboratory tests for both kinds of products show that the latter can be used as aggregates for lowdensity structural concrete. The former serve as a support material for the catalytic reduction of NO x in exhaust gases. Deposition conditions for Fe-and Pt-nanoparticles are optimized by experimental design, resulting in NO x -conversion rates close to 100%.The valorization of wastes as a prime material to produce a ceramic with interesting technological properties is an option to decrease product costs and represents an environmentally friendly alternative to waste disposal. Diverse waste materials based on Si, Al, Ti, and C have been evaluated to elaborate a cellular or foamy ceramics: slag and fly ash [1] wastes from petrochemical fields, [2] cathode ray tubes, [3] waste glasses, [4] and porcelain tile powder [5] are examples. In the first reference, combustion gases dissolved in the slag are responsible for foaming [1] ; in the second case, ceramic cenospheres were added to generate porosity.[2] The other three studies use small amounts of SiC to achieve the formation of ceramic foams, while Bernardo et al. used waste SiC from polishing operations to produce a glass foam.[6]Release of O 2 by the reduction of Fe 2 O 3 was responsible for foaming in products obtained from waste glass and metallurgical slag, without the need for additional foaming agents.[7]Previous work on the valorization of the sludge produced in water potabilization [8,9] showed that mixing with various amounts of clay and firing in the two-phase temperature range allows producing a cellular ceramic without foaming agents.Mössbauer spectroscopy and thermogravimetric analysis indicate that the slow release of H 2 O by dehydroxylation of ghoethite or lepidocrocite at high temperature is responsible for the foaming of the viscous mixture.[9] A glassy matrix, rich in This communication presents a summary of recent studies, in which the technological applications of this cellular ceramic are explored. High-strength medium-porosity materials was optimized for its use in lightweight structural concrete. This presents a high-volume, low added value application which is optimal, when waste reduction is the main goal.