Bricks in the circular economy

The use of masonry bricks is one of the oldest construction techniques in human history, and the reuse of bricks was already an established practice in antiquity. Today, this practice is gaining importance again in the context of the circular economy. In Germany, more than two-thirds of the residential building stock older than 50 years was built using brick construction. Furthermore, the German construction sector generates around 59.8 million tons of construction waste annually, including about ten million tons of demolition bricks or brick-rich material mixtures. By reusing and recycling bricks, it is possible not only to reduce waste volumes but also to make significant contributions to resource conservation and the reduction of CO₂ emissions. Let us therefore take a closer look at the various possibilities for brick recycling in the following.

Reuse

In terms of the circular economy, the reuse of bricks is a top priority. The decisive material properties for the reuse of bricks, such as compressive strength, water absorption capacity, frost resistance, and chemical resistance, depend on the intended use, and the absence of pollutants must always be guaranteed. Technical testing should be as comprehensive as required for the respective application and must comply with the legal requirements for the reuse of bricks. A prerequisite for reuse is dismantling or demolition that is as selective as possible. Reusing bricks requires significant resources to carefully separate the stones from the mortar without damaging them, as damaged bricks can lose their load-bearing capacity and can no longer be used as high-quality building material. The type of mortar used therefore plays a special role here. With clay mortar, for example, selective separation of the bricks is easily possible. Highly sandy lime mortars also allow for this, but require more effort. With chemically strong-bonding mortars such as cement mortar, separation is significantly more difficult because the mortar adheres firmly to the bricks. Innovative developments such as the clay thin-bed mortar from the company Claytec will play a pioneering role in the reuse of bricks in the future.

Recycling

If reuse of the bricks is not possible after their first life cycle, recycling takes place. Aggregates can be produced from demolition bricks and kiln rejects from brick production, which are used in road and path construction. The majority of old bricks are used in road construction for bound and unbound surface layers. Other areas of application for brick chippings and sand include sports field construction, such as tennis courts, and use as a planting substrate in landscaping. In addition, processed brick chippings can serve as a raw material substitute, for example in the production of recycled concrete (R-concrete) or new bricks. This allows for the partial substitution of aggregates such as gravel or crushed primary rock. Modern sorting and processing techniques make it possible to process bricks in several steps and reintroduce them into the material cycle.

A world full of good ideas

FRONT Materials

The company FRONT, formerly known as StoneCycling, is a pioneer in the production of bricks from recycled waste materials. The company produces so-called "WasteBasedBricks," which consist of at least 60% recycled construction and industrial waste, including brick and ceramic waste. The manufacturing process involves collecting, sorting, crushing, and mixing these materials before the bricks are molded, dried, and fired. The finished bricks also undergo various testing procedures and are suitable for both indoor and outdoor use, meeting European safety standards. FRONT aims to produce completely climate-neutral bricks by 2026 by relying on alternative energy sources for the firing process.

Another innovative product from FRONT is the "BioBasedTiles." These tiles are also made from recycled waste materials, but without the conventional firing process, which is associated with significant CO₂ emissions. Instead, the "BioBasedTiles" gain their strength through a biological process in which bacteria use carbon compounds to solidify the material within a few days. Areas of application include wall cladding and flooring.

Cold-pressed bricks from Leipfinger Bader

As part of a research project, the brickworks Leipfinger-Bader has developed a cold-pressed brick made from recycled brick residues and mineral binders. The main component of the brick is brick sand, which is produced during the grinding of precision bricks, as well as other fractions of recycled brick rubble. The cold-pressed brick is formed using a special pressing process and then air-dried, giving it a significantly lower carbon footprint compared to fired bricks. It meets static requirements as well as sound insulation requirements for load-bearing interior walls.