Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Immobilization of lead Pb2+ in blended binders
Permanent solidification of hazardous inorganic waste in cementous composites is commonly known method of their disposal, especially when the recovery of heavy metals from waste stream is not profitable and may present potential danger to natural environment. More and more often, active mineral additives with pozzolana or pozzolana-hydraulic properties are applied during the process of grout and solidificating composite creation. These compounds take active part in hydration process and are favourable during the formation of proper microstructure of solidification matrix. The test results showing the level of immobilization of Pb2+ in blended binders are presented. They confirm that blended mineral binders containing such mineral additives as: silica fly ash, fluidal fly ash, or granulated blast furnace slag may present effective matrix for binding of lead ions in their structures. Implementation of lead ions (1% in relation to binder mass) results in the extension of setting times of binders, as well as in decrease of early compression strengths of mortars. It is a consequence of delaying the hydration process of cementous binders with the addition of Pb(2+) ions, which leads to slower increase of early strength. The extension of setting times of mortars subsidized with lead is connected with the covering of binder grains with lead hydroxide. Immobilization level of Pb(2+) ions in tested binders increases as the time of hardening goes by, which should be related with the changes of microstructure of hardening binders (increase of compression strength). The highest immobilization level was reached for binder IV Pb after 90 days of hydration. The level is higher than the one achieved from matrixes made of Portland cement CEM I. Moreover, it is also necessary to highlight the results received on binder II (40% of fluidal ash). The binder has comparable strength properties to tested Portland cement CEM I and characterises with very high level of lead immobilization, both under the activity of leaching liquid with pH = 7 and with pH = 4. Grinding of matrixes being subjected to tests has important influence on the level of leaching of lead to water extracts - the lower grain-size distribution (surface more developed), the higher concentration of lead ions in eluat. Subjecting the hardened samples of mortars under the influence of low temperatures (frosting and defreezing) does not effect in liberation of significant amounts of Pb(2+) ions from their structure to water environment.
Immobilization of lead Pb2+ in blended binders
Permanent solidification of hazardous inorganic waste in cementous composites is commonly known method of their disposal, especially when the recovery of heavy metals from waste stream is not profitable and may present potential danger to natural environment. More and more often, active mineral additives with pozzolana or pozzolana-hydraulic properties are applied during the process of grout and solidificating composite creation. These compounds take active part in hydration process and are favourable during the formation of proper microstructure of solidification matrix. The test results showing the level of immobilization of Pb2+ in blended binders are presented. They confirm that blended mineral binders containing such mineral additives as: silica fly ash, fluidal fly ash, or granulated blast furnace slag may present effective matrix for binding of lead ions in their structures. Implementation of lead ions (1% in relation to binder mass) results in the extension of setting times of binders, as well as in decrease of early compression strengths of mortars. It is a consequence of delaying the hydration process of cementous binders with the addition of Pb(2+) ions, which leads to slower increase of early strength. The extension of setting times of mortars subsidized with lead is connected with the covering of binder grains with lead hydroxide. Immobilization level of Pb(2+) ions in tested binders increases as the time of hardening goes by, which should be related with the changes of microstructure of hardening binders (increase of compression strength). The highest immobilization level was reached for binder IV Pb after 90 days of hydration. The level is higher than the one achieved from matrixes made of Portland cement CEM I. Moreover, it is also necessary to highlight the results received on binder II (40% of fluidal ash). The binder has comparable strength properties to tested Portland cement CEM I and characterises with very high level of lead immobilization, both under the activity of leaching liquid with pH = 7 and with pH = 4. Grinding of matrixes being subjected to tests has important influence on the level of leaching of lead to water extracts - the lower grain-size distribution (surface more developed), the higher concentration of lead ions in eluat. Subjecting the hardened samples of mortars under the influence of low temperatures (frosting and defreezing) does not effect in liberation of significant amounts of Pb(2+) ions from their structure to water environment.
Immobilization of lead Pb2+ in blended binders
Krol, Anna (Autor:in)
Ibausil, Internationale Baustofftagung, 16 ; 1093-1100
2006
8 Seiten, 2 Bilder, 3 Tabellen, 3 Quellen
Aufsatz (Konferenz)
Englisch
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