This work describes the studies carried out with various industrial wastes and natural byproducts based on the SiO2-Al2O3-CaO system, aimed at extruding ceramic products of industrial interest. Four waste materials were selected and characterised, namely, (i) Al-rich anodising sludge (A-sludge), (ii) sludge from the filtration/clarification of potable water (W-sludge), (iii) sludge generated in marble sawing processes (M-sludge), and (iv) foundry sand (F-sand). Two different formulations were prepared and bodies were shaped by extrusion, after its detailed optimisation. Screw extruded rods were then fired at several temperatures and characterised in terms of relevant functional properties (shrinkage, density and mechanical strength). Their electrical insulating properties were assessed by impedance spectroscopy. The design of interesting technological properties, such as high electrical and mechanical resistance, refractoriness, etc, was found to be easily achievable by controlling the initial batch formulation and/or the sintering schedule.