1/8 Factorial Study of Metal Effects on Acid Neutralization by Cement

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(NO3)3 and ZnCl2, 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.