REALight - Lightweight granulates and FGD gypsum from construction waste and industrial by-products

Resource-efficient circular economy - construction and mineral material cycles (ReMin)

The aim of the project is to develop a reference plant for the production of lightweight granulates from construction and demolition waste with gypsum recovery. A wide range of previously unused or low-level construction and demolition waste and industrial by-products are used as raw materials.

The project is being funded as part of the "Resource-efficient circular economy - construction and mineral material cycles (ReMin)" funding measure. "ReMin" is part of the BMBF research concept "Resource-efficient circular economy" and is aimed at resource-efficient construction and the expanded use of mineral secondary raw materials from construction waste, slag, ash and mining residues.

A new way of recycling building materials

In Germany, more than 50 million tons of construction waste consisting of concrete and masonry rubble are produced every year. The further recycling of mixed masonry rubble is severely restricted due to the sometimes high sulphate content resulting from building materials used in interior construction, highly fluctuating physical properties or the presence of other impurities. The use of secondary raw materials obtained from this is therefore usually limited to applications with low quality requirements. If the sulphate content is too high, which would damage the concrete, the only remaining option is often to landfill the construction waste, which is cost-intensive and not in line with the circular economy.

The aim of the REALight project is therefore to develop a reference plant for the user-optimized production of lightweight granulates from mineral construction and demolition waste with gypsum recovery as well as the technological expansion of the process to include a wide range of mineral material flows and industrial by-products such as slag.

The combination of classic mechanical and modern thermal processes breaks new ground in the recycling of building materials. The use of a rotary kiln to produce light granulates from waste containing clay ceramics with simultaneous flue gas desulphurization is innovative. In this way, unwanted sulphates in many construction products are converted into FGD gypsum, which is in high demand. A topic that is highly topical with the coal phase-out and the associated elimination of large quantities of gypsum from flue gas desulphurization plants (FGD gypsum).

The reference plant is the prerequisite for

- the transfer of the product and process idea into practice, - the demonstration of sulphate separation and recovery from gypsum-containing feed material, - the extension of the technological approach to other mineral waste streams to broaden the raw material base, - the intelligent coupling of specific material streams - with the aim of the production of sufficient quantities of lightweight granulates in order to characterize them, to test them in known applications and to develop new fields of application, - the balancing of the process as a basis for an economic and ecological assessment.

In order to broaden the raw material base, the suitability of various mineral wastes will be examined in a raw material assessment. Lightweight aggregates (LWA) are produced, for which there are already signs of a shortage in Germany. The deposits of natural LWA and primary raw materials for the production of lightweight aggregates are limited. REALight is intended to be groundbreaking for the recycling of building materials by closing cycles.

Division of tasks among the REALight project partners

Twelve project partners from various areas of building material production and application, waste processing, process engineering and research and development are working on the following key areas: - LWA production technology from masonry rubble - Sulphate removal from secondary mineral material streams and production of FGD gypsum - Raw material assessment to expand the raw material base beyond masonry rubble, including necessary pre-treatment/preparation - Evaluation and testing of the performance stability of the new LWA - Application of LWA in lightweight concretes, mortars and unbound systems

Transfer into practice

The participating companies benefit from the expansion of their scope of services and their product range and can use and market a unique product with LWA made entirely from residual materials. The fields of application are broadly diversified with the areas of lightweight concretes, dry mortar/mortar systems, fills/substrate components and supplementary stone compounds/repair mortars in monument conservation. The project also strengthens the scientific expertise of research institutions and universities.

Funding measure
Resource-efficient circular economy - construction and mineral material cycles (ReMin)

Project title
REALight - Lightweight granulates and FGD gypsum from construction and demolition waste and industrial by-products


Funding reference

Funding volume of the consortium
1,916,758 euros

Dipl.-Ing. Alexander Schnell | Bauhaus-Universität Weimar
Coudraystr. 11 | 99423 Weimar
Phone: 03643 58-4608

Project participants
Federal Institute for Materials Research and Testing; IAB Institut für angewandte Bauforschung Weimar gGmbH; TU Clausthal; T.B.R. Teltower Baustoffrecycling GmbH; Mendiger Basalt Schmitz Naturstein GmbH; BNB Beton und Naturstein Babelsberg GmbH; Sievert Baustoffe GmbH; Heidemann Recycling Thüringen GmbH; Opus Denkmalpflege GmbH; IBUtec advanced materials AG; HanseGrand Klimabaustoffe e.K.

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