Masonry rubble for resource-conserving construction

The construction industry is one of the largest consumers of natural resources and energy in the German economy. This is ecologically and economically viable because the components and structures have a significantly longer technical life span compared with other economic goods, and if high recycling rates can be achieved after demolition. The mass building material concrete plays a central role in terms of savings in the construction industry. In addition to the reduction of the energy-intensive clinker content, the use of proportional substitutions of natural aggregates – with the largest share found in concrete – offer great potential compared to recyclate. Aggregates too are a scarce resource; the expansion or even opening of new quarries and mines is becoming increasingly difficult as there are competing land use claims in our densely populated country. In fact, R concretes are one option for actually closing material life cycles, and this is the objective of the project.

Although the requirements of RC aggregates and R concretes are regulated in Germany, these ecologically valuable and sustainable concretes are rarely used in building construction. While R concretes using type 1 aggregate (= recycled concrete demolition) are at least used regionally after successful pilot projects (Baden-Württemberg, Berlin, Rhineland-Palatinate), there are still major barriers to the use of aggregates made from masonry rubble. These obstacles are the result of inadequate awareness of R concrete with type 2 RC aggregate among planners and building contractors, the potential gypsum content of the demolition materials, the fluctuating water absorption of the different brick grades, and insufficient experience and forecasts relating of the durability of the concrete in the corresponding exposure classes.

These issues form the basis of this multidisciplinary project wich involves experts in processing technology, construction material ecology and concrete technology, and investigates the following areas:

• Investigation and evaluation of type 2 RC aggregate from a recycler beyond the previous status of the regulations, and documentation of the fluctuation range
• Development of a simple procedure for quality control of type 2 RC aggregate for the demolition company or recycler
• Manufacturing concrete with real type 2 RC aggregate, and testing all relevant characteristics and durability on the basis of the frost resistance
• Drawing up life cycle assessments and economic consideration of tested recipes as a contribution to environmental protection
• Investigation and evaluation of the multifunction blocks known as “Ökostones” made by the company Feess after several years of outdoor exposure, and demonstration of potential further uses of type 2 RC aggregates