Effect of heavy metals and water content on the strength of magnesium phosphate cements.

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.

[1]  Zhu Ding,et al.  Effect of aggregates and water contents on the properties of magnesium phospho-silicate cement , 2005 .

[2]  P. K. Mehta.  Concrete: Structure, Properties, and Materials , 1992 .

[3]  Miss A.O. Penney.  (b) , 1974, The New Yale Book of Quotations.

[4]  Julia A. Stegemann,et al.  Summary of an investigation of test methods for solidified waste evaluation , 1990 .

[5]  Quanbing Yang,et al.  Properties and applications of magnesia–phosphate cement mortar for rapid repair of concrete , 2000 .

[6]  Jaime Planas,et al.  Review of the splitting-test standards from a fracture mechanics point of view , 2001 .

[7]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[8]  Arun S. Wagh,et al.  Ceramicrete stabilization of low-level mixed wastes - a complete story , 1997 .

[9]  J. M. Chimenos,et al.  Removal of ammonium and phosphates from wastewater resulting from the process of cochineal extraction using MgO-containing by-product. , 2003, Water research.

[10]  Quanbing Yang,et al.  Factors influencing properties of phosphate cement-based binder for rapid repair of concrete , 1999 .

[11]  R. Comans,et al.  The leaching of major and trace elements from MSWI bottom ash as a function of pH and time , 2006 .

[12]  Julia A. Stegemann,et al.  A proposed protocol for evaluation of solidified wastes , 1992 .

[13]  A. W. Frazier,et al.  Solubility products of magnesium ammonium and magnesium potassium phosphates , 1963 .

[14]  L. Llanes,et al.  Fracture variability and R-curve behavior in yttria-stabilized zirconia ceramics , 2001 .

[15]  J. Planell,et al.  Compressive strength and diametral tensile strength of some calcium-orthophosphate cements: a pilot study , 1993 .

[16]  R. Stevens,et al.  Effect of Water Content on the Structure and Mechanical Properties of Magnesia‐Phosphate Cement Mortar , 2005 .

[17]  F. Abbona,et al.  Crystallization of two magnesium phosphates, struvite and newberyite: Effect of pH and concentration , 1982 .

[18]  J. H. Sharp,et al.  Chemical reactions between magnesia and aluminium orthophosphate to form magnesia-phosphate cements , 1989 .

[19]  Z. Ding,et al.  Chemical Durability Investigation of Magnesium Phosphosilicate Cement , 2005 .

[20]  Arun S. Wagh,et al.  Magnesium potassium phosphate ceramic for 99Tc immobilization , 2006 .

[21]  H. Itoh,et al.  REACTION OF ALKYL ARYL SULFOXIDE WITH METHYL PHENYL N-CHLOROSULFOXIMIDE. DIRECT SYNTHESIS OF OPTICALLY ACTIVE α-CHLORO SULFOXIDE WITH OPTICALLY ACTIVE N-CHLOROSULFOXIMIDE , 1978 .

[22]  D. Singh,et al.  HIGH STRENGTH PHOSPHATE CEMENT USING INDUSTRIAL BYPRODUCT ASHES , 1999 .