Concrete and reinforced-concrete pipes can already be used as a source of recycled aggregate. However, a true circular economy requires the use of the highest possible proportion of recycled concrete rubble in pipe production. Therefore, a pilot project with Sika, the Federal Association of Concrete Sewer Systems (FBS) and the Röser Group explored whether 100% recycling of concrete rubble was feasible from a production and concrete technology perspective (Fig. 1). The individual steps, from processing the concrete rubble using the reCO2ver process, through preliminary laboratory tests to industrial test production, led to important findings that could significantly revolutionize the concrete circular economy. This article focuses on the problem and the findings gained in laboratory tests.