Durability of Cement Matrices Used for Stabilization of Hazardous Wastes

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Title: Durability of Cement Matrices Used for Stabilization of Hazardous Wastes

Author(s): J. Madrid, J. M. Diez, S. Goiii and A. Marcias

Publication: Special Publication

Volume: 170

Issue:

Appears on pages(s): 1527-1550

Keywords: Acids; blast furnace slag; cadmium; durability; lead (metal); seawater; stabilization.

Date: 7/1/1997

Abstract:
The durability of cement-stabilized specimens in various aggressive media were studied by means of the Koch and Steinegger test over 56 days at 20°C. Prismatic lxlx6cm samples of normal portland cement (OPC) and normal portland cement with 80% ground granulated blast furnace slag (OPC/BFS) addition, were prepared mixing them with water containing 5,000 ppm Pb2+ (OPC samples), 15,000 ppm Pb2+ (OPC/BFS samples) or 50,000 ppm Cd 2+. Those specimens were immersed in the aggressive solutions tested: a buffered AcH/Ac- medium, a NaCl 0.45M + Na2SO4 0.03M solution (SO4= and Cl- concentrations equivalent to those of the sea water) and deionized water as reference. In addition, the concentration of toxic metals in the aggresive media. was measured I Changes into microstructure and flexural strength were evaluated by X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP). The pore fluid solution extracted from specimens and the leachate solutions were analyzed for Pb2+, Cd2+, Ca2+, Na+,K+, SO4 and Cl-ions. Results show that normal portland cement and blast furnace slag blended cements are durable matrices in saline medium similar to sea water, but undergo an acid attack with formation of a porous degradation coating and dissolution of toxics metals in the acid medium of AcH/Ac- buffer solution.