Center for Light and Environmentally-Friendly Structures ZELUBA®

Research project

ReMatBuilt – Efficient and resource-saving building products from construction waste and plant residues 

The global construction industry devours enormous quantities of fresh raw materials, in particular in the production of concrete. How can resource efficiency be improved? In collaboration with our project partners in Germany and China, we are developing sustainable concrete building materials and high-performance construction elements on the basis of construction and demolition waste as well as plant-based production residues. One particular focus here is the identification of suitable recycling processes as well as the adaptation of the building products and all the process steps for the German and Chinese markets. We thereby offer a solution that can be rapidly implemented in order to significantly increase the proportion of renewable raw materials in the construction industry. Simultaneously, we are creating economically interesting perspectives for the agricultural and forestry industries, recycling enterprises and mechanical-engineering companies, as well as for the insulation and construction industries.  

Simplified illustration of a house with a door and a window as a 3D graphic with dimensions.
© Fraunhofer WKI | Libo Yan
Scale model of a house with walls made from recycled concrete and a natural-fiber-reinforced composite element comprised of wood and recycled concrete as the story floor. The recycled concrete is based on rice-husk ash as a cement substitute and aggregates from concrete/masonry waste instead of gravel.
3D graphic of a wall with a masonry-like structure. The cavities of the individual bricks show a yellow filling.
© Fraunhofer WKI | Manuela Lingnau
Wall system for one- to two-story residential buildings made from prefabricated recycled-concrete blocks with integrated insulation made from straw which is produced, for example, as waste from wheat or rice cultivation.

To improve the resource efficiency of building products, we are pursuing the following approaches in this project:

  • Utilization of used concrete and masonry waste (“building rubble”) as coarse and fine aggregates for the production of recycled concrete
  • Utilization of wood chips from waste wood as natural coarse aggregates for the production of lightweight recycled concrete
  • Utilization of rice-husk ash from the rice-milling process as a substitute for conventional Portland cement as well as to improve strength, durability, thermal and acoustic insulation
  • Utilization of natural-fiber plant textiles as an internal reinforcing material for the developed recycled concrete in order to improve its strength and ductility
  • Combination of solutions: Developing a particularly lightweight and resource-efficient high-performance concrete using waste-wood chips, rice-husk ash, and natural-fiber reinforcement
  • Utilization of rice straw, wheat straw and wood sawdust to produce sustainable insulation panels
  • Combination of recycled-concrete and straw insulation panels to produce a wall system of prefabricated insulated blocks
  • Combination of laminated veneer lumber and cross-laminated timber with the developed recycled concrete for the production of novel wood-concrete composite systems as story floor

 

Social relevance

As a result of the global construction boom, there is an immense, rapidly growing demand for cement and aggregates for concrete production. Cement consists of finite minerals. Cement production accounts for eight percent of global carbon dioxide emissions - more than all air traffic combined. Rice is the most widely used food in the world. To date, the husks have largely remained unutilized. A particular combustion process produces, in addition to a large amount of energy, rice-husk ash. This is suitable as a cement substitute.

Gravel is used almost exclusively as a concrete aggregate. Gravel is a finite raw material whose extraction is harmful to the environment and which often has to be transported long distances to the concrete plant. Building rubble and waste wood are produced in large quantities everywhere. Until now, they have seldom – if at all – been recycled for construction purposes. 

 

Economic advantages

Waste or raw material? Production waste, which previously yielded relatively little money or even had to be disposed of at high cost, is becoming valuable as building material and can command high prices. An interesting side effect for the agricultural sector is that holistic recycling makes the cultivation of annual and perennial plants more lucrative.

In order to produce natural fibers and textiles from plant waste, the plants must be harvested and pretreated in a special way. This opens up a new business field for mechanical-engineering companies.

For housing-construction companies, entirely new opportunities are being created for sustainable building. The hybrid building elements which we are developing in this project combine the advantages of plant-based building materials and concrete. Our aim is to create durable building elements with excellent mechanical and hygrothermal properties which are easy to process and which fulfill the fire-safety regulations. In this way, we are expanding the possibilities for cost-effective construction under increasingly stringent sustainability requirements.

Project partners#

  • Institute of Building Materials, Concrete Construction and Fire Safety (iBMB) of the TU Braunschweig
  • AgroMaterialSupport
  • Entsorgungstechnik-Bavaria GmbH
  • Advanced Compounding Rudolstadt GmbH
  • Hunan University
  • Xuchang Jinke Resource Recycling Co., Ltd.

Funding#

Official project title: Improved resource efficiency of renewable raw materials through the utilization of agricultural and forestry waste as well as construction and demolition waste for a sustainable building environment

Funding body: German Federal Ministry of Education and Research (BMBF)

Funding reference: 031B0914A, 031B0914B

Project management: Project Management Jülich (PtJ)

Duration: 1.3.2020 to 28.2.2023