Recycling gypsum: processing building materials instead of disposing of them in landfills

Already today, up to ten percent of gypsum - a building material used to make walls, ceilings and floors - is contained in the fabric of buildings in this country. After a building has been demolished, up till now the gypsum waste has largely been landfilled, because it causes huge problems when recovering it to make recycled building materials (so-called RC building materials). Its use in RC building materials is therefore subject to extremely stringent specifications (DIN 4226-100): Type 1 RC building materials (concrete chippings, crushed concrete sand), for example, may only contain 0.2 percent by mass of gypsum, while Type 2 RC building materials (building chippings/crushed building sand) may contain up to 0.5 percent by mass.

If these values are exceeded, the building rubble must be landfilled. In Germany alone, around five million metric tons of fine fractions (< 2 millimeters) of building rubble are produced each year, which are sent directly to landfills, partly because of the gypsum problem. However, even landfilling is difficult due to the high sulfate concentrations that leach out and contaminate the groundwater. In addition to building materials made purely from gypsum, building materials that contain sulfates, such as aerated concrete, are also affected. 

New chemical processing method developed

Based on the chemical analyses of building rubble and model walls, it is currently assumed that the average gypsum content in buildings (and thus also in building rubble) is 3.6 percent by mass. In some cases, however, a gypsum content of up to 10 percent by mass has been found in building rubble.

Since sulfate-containing mineral phases in most building materials are chemically bound rather than physically, only chemical processing methods can be used to recycle them. Our experts have developed such a processing method and have also constructed a demonstrator on a laboratory scale. Get in touch with us, we are more than happy to be of assistance!