title: Effect of heavy metals and water content on the strength of magnesium phosphate cements.
abstract: In this paper the mechanical properties of magnesium potassium phosphate cements used for the Stabilization/Solidification (S/S) of galvanic wastes were investigated. Surrogate wastes (metal nitrate dissolutions) were employed containing Cd, Cr(III), Cu, Ni, Pb or Zn at a concentration of 25 g dm(-3) and different water-to-solid (W/S) ratios (0.3, 0.4, 0.5 and 0.6 dm(3)kg(-1)) have been employed. Cements were prepared by mixing hard burned magnesia of about 70% purity with potassium dihydrogen phosphate. Compressive strength and tensile strength of specimens were determined. In addition the volume of permeable voids was measured. It was found that when comparing pastes that the volume of permeable voids increases and mechanical strength decreases with the increase of water-to-solid ratio (W/S). Nevertheless pastes with the same material proportions containing different metals show different mechanical strength values. The hydration products were analyzed by XRD. With the increase of water content not previously reported hydration compound was detected: bobierrite.
authors.affiliation: Department of Mechanical Engineering, Technical University of Catalonia, 08028 Barcelona, Spain. irene.buj@upc.edu
authors.forename: Irene
authors.initials: I
authors.lastname: Buj
authors.forename: Josep
authors.initials: J
authors.lastname: Torras
authors.forename: Daniel
authors.initials: D
authors.lastname: Casellas
authors.forename: Miquel
authors.initials: M
authors.lastname: Rovira
authors.forename: Joan
authors.initials: J
authors.lastname: de Pablo
mesh_terms: D019245:Compressive Strength; D003247:Conservation of Natural Resources / Q000379:methods*; D007220:Industrial Waste / Q000517:prevention & control; D017616:Magnesium Compounds / Q000737:chemistry*; D008420:Manufactured Materials / Q000592:standards*; D019216:Metals, Heavy / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry*; D012037:Refuse Disposal; D013718:Tensile Strength; D014867:Water / Q000737:chemistry*
chemical_list: D007220:Industrial Waste; D017616:Magnesium Compounds; D019216:Metals, Heavy; D010710:Phosphates; D014867:Water; C030781:magnesium phosphate