Electrochemical Stability of Embedded Steel and Toxic Elements in Fly Ash/Cement Beds

Abstract

ABSTRACTThe electrochemical stability in fly ash/cement beds is of major concern to the durability of construction metals (iron or steel) embedded in the matrix as well as the stabilization (fixation) of toxic elements. The electrochemical stabilities were evaluated by measuring the redox potential as a function of both time and leach solution. For simulating the field conditions, the measurements were made on leachates of a prepared solution simulating rain composition in the area of application and results were contrasted to those obtained on leachates of standard deionized water. Two leaching techniques were used: the standard EPA-EP test; a test developed at MRL/PSU for simulating field conditions in which leaching fluids are pumped up a fly ash/cement column. The redox potentials (based on hydrogen scale), Eh's, were plotted vs. pH of the leachates and the regions of stability of various construction materials and toxic elements were predicted. Tafel plots were also constructed for iron in contact with different leachates, and its corrosion rate was estimated.