Abstract for presentation at Advances in Cement and Concrete Sustainability the 2 -7 July 2006 in Davos, Switzerland
Some aspects of the use of sludge incinerator ash for the production of concrete
Jørn Bødker, Danish Technological Institute, Gregersensvej, DK-2630 Taastrup, Denmark
Claus Pade, Danish Technological Institute, Gregersensvej, DK-2630 Taastrup, Denmark
Bo Neergaard Jacobsen, Avedoere Wastewater Services, Denmark
Dan Kjersgaard, Avedoere Wastewater Services, Denmark
Kim Rindel, Lynettefællesskabet I/S, Denmark
Freddie Larsen, Unicon, Denmark
Incineration of sludge from biological wastewater treatment plants leaves a waste material with some of the same characteristic as fly ash from coal fired power plants. The sludge incinerator ash (SIA) represents an environmental problem as it is typically landfilled the same way traditional power plant fly ash is or was prior to finding wide-spread use in the production of concrete. If the SIA could also be used for the production of concrete without adversely affect the properties of the fresh and hardened concrete it would solve an environmental problem. Using SIA in the production of ready mixed concrete has been practiced in Denmark in small scale for a few years particular with concrete for passive environment classes. However there exist a number of barriers for an extended utilization of SIA in concrete, e.g. the lack of documentation of the environmental impact with respect to leaching of heavy metals from the concrete, as well as the limited documentation of the influence of SIA on the properties of concrete. The Danish Technological Institute has carried out a few SIA concrete projects funded by the Danish EPA, and recently been involved as subcontractor to the project “BioCrete” partly funded by The European Commission-LIFE Program. This paper presents the “BioCrete” project and some of the results of a recent investigation of the SIA concrete in a Danish highway bridge that was cast in 2002. The results include a condition survey including e.g. strength development, petrographic examination, chloride penetration profiles, and carbonation depths, as well as a study of the heavy metal leaching characteristics of the concrete compared to laboratory cast specimens. Accelerated carbonation of the SIA concrete prior to leaching tests had a pronounced effect of the rates of leaching for some heavy metals, i.e. the leaching of chromium was increased by a factor of 10, whereas the leaching of barium was reduced by a factor of 100 or more.