DETERMINATION OF THE TENSILE STRENGTH OF MAGNESIUM PHOSPHATE CEMENTS CONTAINING DIFFERENT METALS USING THE BRAZILIAN TEST

Surface treatment processes like electrolytic or electroless plating provide coatings to metallic parts improving some of their properties like corrosion resistance, wear resistance and appearance [1]. Such processes use baths containing high concentration of heavy metals like chromium, nickel, zinc, etc. When exhausted, the bath becomes a hazardous waste which has to be properly managed. An option for the valorization of the waste is manufacturing of magnesium phosphate cement parts that may be cast in order to obtain road walls or as a base for roads [2]. The stabilized waste may also be disposed at a landfill. In order to know the performance of the material, the strength of the specimens is usually determined. Pastes containing different heavy metals (cadmium, copper, chromium, nickel, lead and zinc) were prepared with a metal concentration of 25000 ppm, a water-to-solid ratio(W/S) of 0.3, 0.4, 0.5 (0.4, 0.5 and 0.6 for Cr) and a magnesium oxide content of 50 % in weight of the total solid. They were allowed to solidify and after 10 months of curing. After that, disks were cut and they were subjected to an indirect tensile strength test (Brazilian test or splitting test) [3]. In general, tensile strength decreased with increasing water content as expected. The specimens prepared with a water-to-solid ratio (W/S) of 0.3 showed relatively high tensile strength values.