Use of fine fraction of Waste-to-Energy Bottom Ash as aerating agent substitute in aerated concrete
BROSSAT M. 1, LUPSEA-TOADER M. 1, PRUD'HOMME E. 2, BLANC D. 1, DE BRAUER C. 1
1 Univ Lyon, INSA Lyon, DEEP, EA7429, Villeurbanne, France; 2 Univ Lyon, INSA Lyon, MATEIS, UMR 5510, Villeurbanne, France
Each year, in Europe, nearly 150 Mt of waste are incinerated producing over 17Mt of Waste-To-Energy Bottom Ash (WtE-BA). WtE-BA can be used in the construction sector as road base material. However, 46 % of it is landfilled because of lack of valorization schemes. Therefore, previous studies worked on alternative use of WtE-BA, particularly as a substitute for concretes’ raw materials. Several studies, showed that addition of WtE-BA caused swelling of concrete due to oxidation of reducing metals such as aluminum. In addition, the fine fraction (particles < 2mm) of the total WtE-BA (that represents around 30-40 %) is even more seldom used because of its high content in heavy metal. However, its chemical composition and potential pozzolanic activity are two arguments in favor of its uses in concrete. In addition, studies show that those pollutants can be stabilized into concretes’ solid matrix. In this study, to take advantage of the oxidation of metallic aluminum, fine fraction is used as a substitute of aerating agent for the production of aerated concrete. The aim is to produce a light and resistant concrete that restrains pollutants of WtE-BA from leaching. Furthermore, this study aims to assess the influence of the variability of WtE-BA used. This is why 2 different WtE-BA from 2 different incineration plants located in Belgium and Czech Republic have been used in different formulations of WtE-BA concretes.
In this study, properties of WtE-BA concretes are compared with two control concretes: an aerated (produced using 0.5 % cement weight of Al0 powder) and a traditional concrete. Samples were produced using cement CEM I 52,5 N and were cast in cylindrical molds of 11 cm height and 22 cm of diameter. The properties assessed are:
mechanical strength (through compressive strength after 7, 28 and 90 days of curing according to EN 12390-3),
density,
thermal resistance (using a Hot disk),
leaching potential (through a Dynamic Surface Leaching Test (DLST) according to EN 16637-2),
porosity and mineralogy analysis using an X-Ray tomograph and a Scanning Electron Microscope.
All those properties have been assessed after 90 days of curing. In addition, mechanical strength has been assessed after 7 and 28 days of curing too.
Results show that WtE-BA concrete comparable compressive strength (13.2 vs 11.9 MPa) and density as aerated concrete. However, because of its less developed porous network and more compact matrix, WtE-BA concrete is less insulating than aerated concrete. No significant difference has been observed between concretes using WtE-BA from different incineration plants meaning that the variability of WtE-BA does not influence properties of the concrete. Finally, leaching tests show that pollutants are well stabilized into the concretes’ matrix. Optimization of properties could be expected using an autoclave, this could be of interest for future studies.
Keywords: Concrete, Aerating Agent, Waste-to-Energy Bottom Ash, Valorization, Secondary Raw Material
