Systematic trends and empirical modeling of lead uptake by cements and cement minerals

摘要

Uptake of Pb was investigated for different hydrated fresh and leached Portland and high-alumina cements,different CSH phases including tobermorite,portlandite,as well as for several relevant cement Al-mericals.Except for highly degraded cement,CSH minerals are the most important phases for Pb uptake.A systematic analysis of our data and a comparison with recent literautre data for CSH phases [1] shows that Pb uptake is characterized by three trends:1) between pH 10-13,Pb uptake decreases with increasing pH,2) Pb uptake increases with increasing Fe content in the clinker,and 3) Pb uptake is dependent on the Pb concentration in the solution.Following these findings,an empirical model was developed based on regression analyses of uptake vs.Pb concentration,pH,and Fe content in the clinker.The resulting relation can predict K_d values for a large rnage of fresh and leached cements,as well as for individual cement minerals under different experimental conditions.Model application to independent data on cement phases,whole cement,and mortar gave very good agreements.