Influence of the addition of grinding dust to a magnesium phosphate cement matrix

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Magnesium phosphate cement materials were prepared by reacting magnesium oxide with water-solublephosphates such as mono-ammonium dihydrogen phosphate (ADP), which solidified at ambienttemperature through the formation of hydrated phases in the material. Cylindrical specimens of magnesiumphosphate cement were molded and varying amounts (0–40% weight) of grinding dust, wastegenerated in the clutch disc finishing process by grinding and polishing, were added to the ceramicmatrices. The influence of the addition of grinding dust on the characteristics of the cement compositionswas verified in terms of setting time, apparent porosity, density and leaching/solubilizationtests. The setting time was analyzed according to NM 65 (the Vicat needle) and by indirect calorimetricmeasurements, the apparent porosity and density of the materials were analyzed by the waterimmersion method, based on the Archimedes principle. Using an Instron 5500R universal testingmachine, various analyses were made to ascertain how the different waste contents in the compositionsaffected the mechanical strength (axial compression and tensile strength by diametral compression).The results obtained proved highly satisfactory for the application of this waste as an additivein magnesium phosphate mortars. The addition of grinding dust to the magnesium phosphate cementmatrix did not affect the formation of new phases or the setting time to any appreciable extent, butan increase in grinding dust content led to an initial increase in strength up to a given limit (about30% of waste).