Keestrack machines help build house out of 75% C&D waste

The German company Büscher started in 1961 as a concrete plant and their business grew with, among others, a container service. In 2023, so many years later, Büscher is building a complete house out of 75 percent recycled construction and demolition waste. The load-bearing and non-load-bearing interior wall elements are made of 100 percent recycled aggregates.

They didn't just prove it is possible but also got approval from the Deutsches Institut für Bautechnik (DIBt). The German Federal Association for Building Materials gave their approval to use up to 100 percent of recycled aggregates, including crushed sand similar to type 3, to be used in their prefab load-bearing and non-load-bearing interior wall elements in exposure classes XC1 and X0 (dry).

In 1961 Büscher made concrete like everybody else; from gravel, sand, cement, and water. Now, they have changed the recipe to 100 percent construction and demolition (C&D) waste to replace the sand and gravel completely and produce prefab load-bearing and non-load-bearing interior wall elements. The outside walls are not made out of recycled materials.

Due to their container service, Büscher received a lot of C&D waste which they normally recycled into aggregates for road construction. As this material was difficult to sell and available in high stock quantities the brothers Wolfgang & Hans-Jürgen Büscher started to look at how this material could be re-used and came to the idea to use it as raw material for prefab concrete and concrete elements.

The idea was a sustainable idea, but it was hard to convince specialists in the field and authorities that this could be the future. Getting 100 percent prefab concrete certified was difficult, and took them eight years of Research and Development to approval as most people didn't believe it was possible.

"Concrete specialists, laboratories, and certification specialists were very doubtful this could be done. They all said it is impossible and not legal," says Wolfgang Büscher.

Büscher asked researchers from laboratories and universities to scientifically prove what the material is capable of and what it's not. They gave the parameters on what they wanted to achieve with the material and let them research if it stands the tests.

"By now all scientific research has been done and it shows exactly what is possible with the 100 percent recycled prefab concrete and concrete elements. The new material functions perfect and the recipe has changed at Büscher," says Hans-Jürgen Büscher.

"The quality is good because the company Büscher took the right measures from the acceptance of the construction and demolition waste, the processing of the material and the use in the prefab concrete and concrete elements," says Prof. Dr.-Ing. Wolfgang Breit of the Technical University Kaiserslautern.

The main advantage of this certified production process is the efficiency of resources. They are using local highly available cheap C&D material and produce a sustainable, climate-neutral product with less CO2 emission, saving as well on transport costs as the material at hand can be used.

"No costly raw materials are used so the price of the end products is also cheaper, a real win/win situation," says Thomas Overbeeke, operations manager at Büscher.

It took them eight years of scientific research to prove a house can be sustainably built from fully recycled material, even at lower costs. While the research took a while, it took them only four months to build the complete three-family house, build with paint-ready prefab elements. Piping and electricity are all integrated into the prefab panels which have a smooth surface so no plaster is needed. Now the first house is built out of 100 percent recycled natural mineral substitutes in the load-bearing and non-load-bearing interior wall elements. And when it is time to demolish it, it will be recycled into new concrete using the Büscher method.

Büscher is minimizing the ecological footprint and is looking to close the material cycle for the circular economy. This is also the reason their factory and recycling site are powered by solar panels. The choice to use Keestrack crushing and screening equipment is also driven by this idea. Oppermann & Fuss, a Keestrack dealer in Germany, has advised Büscher which ZERO equipment was the best fit for their applications and capacity. Plus, choosing the right options is essential in this specific application.

A sustainable product should be produced with sustainable production equipment. As the Büscher site is equipped with solar panels delivering up to 323 kW/h of renewable electricity it is used to power the concrete factory but also to the Keestrack R3e ZERO impact crusher and the K4e ZERO screen. Both Keestrack machines are fully electric and are powered by renewable energy. The machines do not have a combustion engine onboard.

As the electric motors drive most of the mobile crushing and screening equipment and power, some necessary hydraulics systems both Keestrack machines run with ZERO CO2 emissions.

When plugged into the grid, the R3 and K4 are producing zero carbon emissions. The energy cost will be approximately 152kWh. Operational and maintenance costs will decrease drastically as there is no engine on board to maintain.

The technology, its safety features, and the design of the R3 impact crusher have won several European design prices, one of them being the Red Dot award. The compact and easy-to-transport impact crusher is available in a diesel/hydraulic drive, an electric plug-in drive (with onboard backup diesel gen-set), and a ZERO drive. The ZERO drive version utilizes a fully electric plug-in without a genset backup and has a 250t/h capacity.

The Büscher company choose the ZERO versions to minimize the environmental impact as it runs at zero carbon footprint and can be powered by its own solar energy.

The R3e ZERO is equipped with a vibrating feeder with a pre-screen of 1.200 millimetres by 920 millimetres to optimize crushing results and minimize wear. The machine has an inlet opening of 770 millimetres by 960 millimetres and a rotor diameter of 1.100 millimetres and a rotor width of 920 millimetres. The crusher equipped in a closed circuit with a recirculation conveyor and a precession screen of 3.100 millimetres by 1.400 millimetres produces a defined aggregate product size. The installed wind sifter eliminates contaminations of plastics, wood, or paper and the overband magnet separates the metals. The R3e ZERO weighs 32 tonnes, and its plug-out of 125A, powers the connected K4e ZERO of 28 tonnes.

The K4e ZERO, has high productivity with a capacity of up to 350t/h. The double deck screen box of 4.200 millimetres by 1.500 millimetres, standard heavy-duty plate apron feeder, and a hydraulic adjustable screen angle give it very good screening capabilities. The numerous available options and screen decks make the K4 suitable for each job. At the Büscher recycling site, they choose to have the fine and middle fraction conveyor at the same side of the screen to improve the accessibility for the wheel loader.

Each Keestrack machine is designed to have good service access to minimize maintenance and repair times but at the Keestrack ZERO range there are no engines on board meaning maintenance is strongly reduced.

Both Keestrack machines at Büscher are equipped with remote controls to operate the crusher and screen from the excavator. They both have an integrated water spray system which can be used in case the production is too dusty. Both are equipped with a Keestrack-er UMTS system. The telematics software system provides real-time data and analytics. The system enables you to check the location of the machines and if they are working correctly. All aspects of a machine can be checked and if necessary, remote updates to the software can be made. It is possible to run diagnostic tests for all components including the feeder, screen, crusher, and conveyors.

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Website: keestrack.com