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The acid neutralization capacity of a cement/waste product is important because the integrity of the monolithic matrix and contaminant precipitation are dependent on the maintenance of alkaline conditions. A 1/8 fractional factorial experiment was used to selectively examine the main effects of seven pure metal compounds on strength development and acid neutralization capacity of portland cement paste and to obtain information regarding interactions between the compounds. The hydration products in a portland cement paste appear as plateaus in its titration curve. Metal contaminants were found to affect the pH and acid neutralization capacities of these plateaus, suggesting that they change the hydration products. Cr(NO(sub 3))(sub 3) and ZnCl(sub 2), which exhibited individual effects and also interacted, caused the predominant effects. Comparison between predictions by a simple empirical linear model based on these contaminants and acid neutralization capacity of a real solidified metal plating waste showed that additional factors play an important role in real wastes.

A marine environment may be characterized by tidal, submerged, and atmospherically exposed zones. Cathodic protection (CP) of reinforced concrete in the submerged zone may induce reducing conditions associated with immunity to corrosion characterized by negative steel potentials. In the atmospheric zone CP induces an improvement in the local environment at the steel, promoting steel passivity, which may be monitored using a potential decay criterion in relatively dry conditions. Many protective effects will persist following the interruption of the current, providing a basis for intermittent CP in the tidal zone. However, conventional criteria may not be reliable in this case. The importance of the current-induced improvement in the tidal zone environment provides justification for the use of a protection current density criterion. The integrated current densities required to arrest high initial corrosion rates are relatively low. Protection criteria may also be based on a positive trend in measured potentials indicative of passivating steel and the induced voltage drop through the concrete cover that drives the removal of chloride ions and sustains a high hydroxyl concentration gradient between the steel and the external environment.

Chloride transport in concrete is often subject to an electric field. This may arise from an internal source, such as the development of a membrane potential, or it may be imposed on the concrete by an external source, as is often the case when electrochemical remediation techniques are applied and accelerated chloride diffusion tests are undertaken. In this work the theory of chloride migration and its practical applications are reviewed. The migration of ions in an electric field differs from other transport processes in that positive and negative ions move in opposite directions, and the condition of electroneutrality does not impose the same constraint on the transport of ions as would otherwise be the case. Well established laws with appropriate boundary conditions have been used to model chloride transport in concrete under electrochemical chloride extraction and cathodic protection conditions, as well as in accelerated chloride diffusion tests. The minimum electric field that will prevent further chloride contamination may be regarded as the threshold requirement for chloride removal and also provides a basis for a corrosion prevention measure in its own right. The quantification of the membrane effects of concrete on the transport of chloride ions and the time dependence of chloride binding and dissolution require further research.